Detroit Locker

Excerpts from NoSpin/detroit locker® OWNER'S MANUAL

Tractech Inc. Logo
(TracTech Inc. - used without permission)

NoSPIN differential with central driver assembly and external springs and retainers; supplied with support case.

  1. Vehicle Performance
  2. Operation
  3. Test for Proper Installation and Operation
  4. Trouble Shooting
  5. Glossary of Terms

This document contains information that will be of specific interest to those who own Detroit NoSPIN differentials.  It also provides considerable information that is of general interest to owners of lockers made by all manufacturers.  It is provided here as a convenience.

NoSpin Warning Sticker

Vehicle Performance
  • The performance of a vehicle equipped with a NoSPIN/Detroit Locker differential is somewhat different from that of a vehicle equipped with a conventional differential. For example:

When turning a corner, the sound of component disengagement and re-engagement may be audible, and the transfer of driving torque from both wheels to one wheel may be noticeable.

When going from drive (acceleration) to coast (deceleration) in a turn, a "metallic" sound may be heard as torque flow is reversed (inside wheel engaged during acceleration; outside wheel engaged during deceleration).

These characteristics are normal because of backlash designed into the NoSPIN differential, which is of a fixed amount (1 to 2 inches of rotation at the tire tread).

Backlash or slack between the driving and driven clutch teeth is an inherent part of the NoSPIN and necessary to permit automatic operation when driving in forward and reverse. The total backlash in the driveline is increased by the amount of the reduction between the ring gear and pinion. If the ring gear pinion ration is 5 to 1, the total backlash in the drivetrain with the NoSPIN would be about 30° . This in turn is increased by clearances between planetary gear, sliding splines, and the ring and pinion gear. We feel that the total driveline slack can amount to as much as 1/4th turn of the driveline without being abnormal, but if it exceeds ¼ turn, other parts in the drivetrain could be checked. Further clarification of operational and performance characteristics is available through Technical Bulliten No. 81-1044. A copy is available by writing to our marketing department.

  • Anything that improperly causes a difference in individual wheel speeds, such as mismatched tire diameters due to differences in tire wear or tire pressure, or unbalanced loading of the vehicle (especially cargo vehicles, or vehicles operated on a side slope) can cause the NoSPIN differential to deliver power to only one side of the vehicle and thus cause steering problems.
The diameter of tires can be adjusted by varying the air pressure of the tires. Match the distance from the top of each tire rim (X) to the pavement (Y). Match the distance from the top of each tire rim to the pavement.
  • When negotiating a turn (outside wheel disengaged), the inside wheel under conditions of poor traction, may receive excessive torque, which could cause it to break traction nomentarily until its speed is equal to the outside wheel. This will result in re-engagement of the outside wheel thus allowing both wheels to be driven. This condition is most noticeable with lightly loaded axles.
  • Certain vehicles equipped with NoSPIN differentials, such as short wheelbase trucks (e.g., under 120" wheelbase) and four wheel drive trucks with a NoSPIN differential in the front steering axle, can experience "understeer" when negotiating a turn under power. Releasing the accelerator will reduce the torque and improve steering.
  • Use extreme caution when accelerating or decelerating on slippery or unstable surfaces. Vehicles/axles equipped with traction differentials are inherently more sensitive to side-slip than vehicles equipped with conventional differentials. Stability can be retained if side-slip occurs by decelerating (letting off the accelerator). CAUTION: DO NOT APPLY THE BRAKE. TO DO SO MAY RESULT IN LOSS OF VEHICLE CONTROL.
  • Braking capacity is reduced when a NoSLIP differential equipped vehicle makes a turn while coasting downhill in that the inside wheel is then disconnected from the driveline. Operating in low gear will allow the engine to act as a retarder and will improve braking capacity.
  • If the vehicle is stationary on a dry surface, easier steering can be achieved by moving the vehicle slightly in either forward or reverse. (Assure that proper steering pressure is maintained.

NoSPIN differential with central driver assembly and external springs and retainers; supplied with support case.



The NoSPIN differential powers both wheels…yet freely permits wheel speed differentiation when required.

Prime functions

  1. Assures 100% of the available torque and increases drawbar pull.
  2. Prevents wheel spin and power loss when one wheel loses traction.
  3. Compensates for differences in wheel travel when turning or operating on uneven surfaces.

The drive axle illustrated below (Fig. 1) is equipped with a NoSPIN differential. Note that there are no spider gears, but rather two drive members, called driven clutch assemblies. They mate with a spider assembly which is driven by the ring gear through the differential support case.

As long as the vehicle is operated in a straight forward or reverse direction over a smooth surface, the driven clutch assemblies remain locked to the spider assembly. The NoSPIN differential allows the whole vehicle to perform as if the axle half-shafts had been welded – the axle is completely locked. This means both wheels turn at the same speed. If one wheel loses traction or leaves the ground, the opposite wheel, which still has traction, continues to drive the vehicle until traction is regained by both wheels. There can be no one-wheel spinout (Fig. 2).

When the vehicle turns a corner, or when one wheel passes over an obstruction, the outside wheel, or the wheel passing over the obstruction, must travel a greater distance and therefore faster than the other wheel. When this occurs, the NoSPIN differential automatically allows for the necessary difference in wheel speed.

During a turn (Fig. 1), the inside driven clutch remains completely engaged with the spider and continues to drive the vehicle. The outside driven clutch automatically disengages from the spider, allowing the outer wheel to turn freely in the turn. When the vehicle completes the turn, the outside driven clutch automatically reengages the spider, as both wheels again travel at the same speed.

Fig. 1
With a NoSPIN differential, during a right turn...
outside driven clutch assembly, elevated by cam ramps, disengaged from spider assembly and overruns at faster speed





side gear

nospin_1.gif (35928 bytes) inside driven clutch assembly remains locked to spider assembly and  travels at ring gear speed





Spider assembly

NoSPIN Differential NoSPIN Differential axle housing

Gear Support Case

Fig. 2
with conventional differential, traction is limited by the spinning wheel
This wheel stops nospin_3.gif (37014 bytes) This wheel spins

With a NoSPIN differential, maximum traction is available to both wheels.  If one wheel loses traction, the opposite wheel will still drive the vehicle

With a NoSPIN differential, this wheel will drive; Detroit NoSPIN Even if this wheel is in mud, on ice or snow, or off the ground!

Test for Proper Installation and Operation

Installation Test

Step 1

With the engine turned off, raise NoSPIN equipped driving axle(s) until all wheels are out of contact with any surface. Place the transmission in gear or park, so that the driveshaft is locked and does not rotate.

Test for forward disengagement:

Step 2

With two people, rotate both wheels rearward as far as possible to lock both wheels.

With two people, rotate both wheels rearward as far as possible to lock both wheels.

Step 3

With the left wheel securely held in the rearward direction, rotate the right wheel slowly forward. A faint indexing or clicking sound should be heard as the NoSPIN disengages on the right side.

With the left wheel securely held in the rearward direction, rotate the right wheel slowly forward. A faint indexing or clicking sound should be heard as the NoSPIN disengages on the right side.

Step 4

With the right wheel slowly rotating forward, the left wheel should be rotated slightly forward. This will lock both wheels.

With the right wheel slowly rotating forward, the left wheel should be rotated slightly forward. This will lock both wheels.

Step 5

Again, rotate both wheels rearward, as far as possible to lock both wheels.

Again, rotate both wheels rearward, as far as possible to lock both wheels.

Step 6

With the right wheel securely held in the rearward direction, rotate the left wheel slowly forward. A faint indexing or clicking sound should be heard as the NoSPIN is disengaged on the left side.

With the right wheel securely held in the rearward direction, rotate the left wheel slowly forward. A faint indexing or clicking sound should be heard as the NoSPIN is disengaged on the left side.

Step 7

With the left wheel slowly rotating forward, the right wheel should be rotated slightly forward. This will lock both wheels.

With the left wheel slowly rotating forward, the right wheel should be rotated slightly forward. This will lock both wheels.

Repeat steps 2-7 except, test for reverse disengagement.

If the above steps are completed successfully and the rotating wheels disengage easily by hand, rotate freely and evenly, lock both wheels when required, and produce faint indexing or clicking sound, then the NoSPIN is properly installed and is functioning correctly.

IF EITHER WHEEL DOES NOT ROTATE FREELY IN EITHER DIRECTION or does not lock both wheels as required, recheck the installation of the NoSPIN in the axle. Also, check hand and foot brakes for possible drag caused by improper adjustment. Be sure that all thrust washers have been removed from the standard differential support case.

To check normal NoSPIN operation, drive the vehicle on a flat surface with good traction, in a right or left circle in forward and reverse to be sure that the outside wheel is free to overrun (i.e. that the outside tire does not scuff.) The clicking or indexing sound may be heard. The sound of gear reengagement may also be heard upon completion of the turn. This is normal.


Operation Test

Check to see that both wheels of each NoSPIN differential equipped axle are driving. Make this test under load, so that engine torque is applied through the NoSPIN differential with the wheels on the ground. One way to achieve this is to drive up against a solid obstruction (on loose dirt or gravel, if possible) and attempt to spin both wheels together. Perform this test in forward and reverse. (Exercise caution when performing this test to avoid damage to vehicle or obstruction). CAUTION: DO NOT OPERATE THE VEHICLE IF BOTH WHEELS OF A NoSPIN/DETROIT LOCKER EQUIPPED AXLE ARE NOT DRIVING. POWER TO ONLY ONE WHEEL CAN CAUSE SERIOUS STEERING PROBLEMS AND LOSS OF VEHICLE CONTROL AND RESULT IN A MISHAP WHICH CAN CAUSE PROPERTY DAMAGE, INJURY, EVEN DEATH.



An important function of an owner/operator in the field is that one of the many hats he is required to wear is the one labeled "trouble shooter".

Troubleshooting can be a very frustrating, elusive job. However, if some basic rules are followed in a systematic order, solutions can be easily obtained.

The following guidelines can be utilized for trouble shooting both on and off the highway vehicle applications. However, some techniques used for on-highway vehicles are not as important for off-highway vehicles:

  1. Before tearing down an axle and differential make sure you get the correct "story" from a reliable source. Then actually try the vehicle yourself…inspect any previously removed components…question associated failures…ask if it has occurred before. In other words, get the facts…and…don’t over-react.
  2. Read the Trouble Shooting Section.
  3. Perform a Functional Check.
  4. Check tire rolling radii. Assure that all tires are within specifications. (This applies primarily to on-highway vehicles.)
  5. If all the previous checks do not reveal the problem or offer a solution, then the NoSPIN must be removed. Upon removal, look for the following:
  1. Contamination in the oil or on the components.
  2. Obvious broken or worn parts.
  3. Mis-Assembly…i.e., retainers installed backwards, thrust washers left in, spring jumped over retainer, etc.
  4. Heavy wear on spider and clutch drive teeth…i.e., Tooth rounding, 5° negative angle gone, corner chipping of teeth. (These components are usually the main areas of wear.)
  5. Telltale signs of eccentric wear, patterns on components, indicating possible cause of shaft problems.
  6. Check NoSPIN assembly for pair-up, hand cam, H.O.R. tension, backlash, etc.
  1. After inspection of the NoSPIN and associated axle components, a new unit should be installed and a complete functional check and vehicle performance check should be made.
  2. If during the visual inspection a solution to the problem is not obtained, the unit should be returned to Tractech, attention of the Customer Services Manager. Call first for a return authorization number.

The following chart will assist owners and operators of NoSPIN differential equipped vehicles to diagnose and correct problems related to vehicle performance. Potential problems are stated on the left; possible causes for those problems are listed, by number, on the right. The explanation of these "problem causes" follows.

Trouble Shooting Section


Possible Cause(s)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Hub studs shearing; rear tire scuffing; axle shaft breakage · ·     ·     · ·         ·  
Steering difficulty; vehicle pulls on straight forward driving or tends to go straight when making turns · · · · ·   ·   ·       · ·  
No differential action; binding in turns ·     · · ·     ·         · ·
Excessive driveline noise* · · · · ·   ·   ·         ·  
Excessive tire wear · · · · · · ·             · ·
Grinding noises ·     · ·     · · ·       ·  
Continuous "clicking" sound in straight forward driving · · ·   ·                    
Excessive backlash in vehicle drivetrain; engine lug or vehicle surge during turns ·         ·   ·   ·          
Tendency to side-slip or "fishtail" on icy roads                     ·        
Sluggish reengagement of NoSPIN differential clutch assemblies                 ·     ·      
Difficulty in turning vehicle from standing start ·     · ·               · ·  
Erratic operation of NoSPIN differential; premature wear or failure of NoSPIN differential components · · · · ·     · · ·   ·   ·  
NOTE: NoSPIN differentials will emit occasional "metallic" sounds due to backlash built into the unit. This is normal! See backlash under Vehicle Performance in the NoSPIN Owners Manual.



Possible Causes for Vehicular Problems

  1. Improper Installation; defective NoSPIN differential. Follow test procedures outlined in the NoSPIN Owners Manual. Correct installation or repair or replace the NoSPIN differential if the vehicle fails any step of the test procedure.
  2. Overloading and/or improper weight distribution. Remove excess weight and redistribute the load from side to side, according to the vehicle/axle manufacturer’s instructions.
  3. Unequal rolling radii of the drive wheel. A smaller rolling radius tire will cause the tire to overrun constantly when power is applied. The other tire (with the larger radii) will do all the driving. Replace tires or adjust tire pressures until rolling radii are equal.
  4. Broken axle shaft. Replace. NOTE: It is possible to operate a NoSPIN equipped vehicle on one axle shaft. However, this practice is not recommended in that serious damage can occur to other axle components.
  5. Bent axle shaft or housing; axle shafts on different center lines. Replace bent axle shafts or housing, or realign hub faces and bolt circles in both the differential carrier and axle housing.
  6. Larger than normal steering angle; short turning radius. Vehicles designed with high turning angles may surge, have steering difficulty and cause tire wear during sharp turns. Reduce maximum turning angle and have the driver decelerate when engine surge begins.
  7. Incorrect wheel alignment. Correct as required.
  8. Worn or defective axle components. Check the condition of the ring gear, pinion gear, bearings, seals, etc. Replace as required.
  9. Foreign matter in axle housing or improper assembly of axle components. Inspect for contamination. Check assembly of axle components.
  10. Incorrect ring and pinion adjustments; worn driveline components (transmission gears, U-joints, etc.) Replace or adjust components as required.
  11. High crown in road; poor traction surface under all drive wheels. The tendency to side-slip or "fishtail" on icy roads sloping towards the curb is more pronounced when using a traction differential than when using a conventional differential. Stability can be retained when side-slip occurs by decelerating (letting off the accelerator). CAUTION: Do not apply the brakes. To do so may result in loss of vehicle control.
  12. High Viscosity Lubricant. In very low temperatures, gear lubricant can thicken and impede the normal function of the NoSPIN differential. Tractech recommends that the axle oil be changed for very cold weather operation to the lightest acceptable lubricant allowable by the axle/vehicle manufacturer. Heat control devices, garaging and a warm up period may also provide relief from this problem in extreme low temperatures.
  13. Low steering cylinder pressure, undersized steering cylinder, excessive angle of articulation, excessive vehicle weight. Correct as required.
  14. Improper application of product. Review application guidelines in the NoSPIN Owners Manual.
  15. Insufficient front axle overrun ratio (lead) for farm tractors (straight frame with front wheel assist power). Take physical measurement, increase to minimum of plus three (+3) percent by increasing tire pressure in front tires and/or reducing tire pressure in rear tires, within the tire manufacturer’s recommendations.


Articulated – Refers to vehicles that are joined in the middle and turn around this joint, as in "articulated farm tractor".

Axle Carrier – The differential and ring and pinion gears are mounted on the axle carrier; the "center section" of the axle housing.

Axle Gear Ratio – The ration between the number of teeth on the ring gear and the number of teeth on the pinion gear (e.g. 3.92:1.00)

Axle Housing - The support member of the axle which sustains the weight of the vehicle and houses the axle carrier assembly.

Backlash – The designed clearance between mating components in the driveline (e.g., gear sets, spine couplings, etc.)

Case Assembly – The differential housing (usually consisting of the two case halves; contains the differential assembly)

Case Bearing (Carrier Bearing) – the bearings that mount to the hubs on the differential support case.

Case Pilot Bore – the locating diameter in the differential case from which the differential side gear is installed.

Center Cam – The control element of the NoSPIN differential. The center cam is used to lift the drive members from engagement by means of cam ramps.

Central Driver – An outer splined member (similar to the spider) having torque carrying teeth on both sides; the "center piece" of the NoSPIN differential.

Clutch Pack Differential – A limited-slip differential which uses friction plates and/or springs to partially reduce wheel spin.

Detroit Locker Differential – Trademark given to "light duty" NoSPIN differentials (NoSPIN and Detroit Locker are operationally identical.) Manufactured by Tractech.

Differential – Axle gear assembly which allows one axle shaft and wheel to turn slower or faster than the other when negotiating a turn.

Differentiation – The different rate of speed between two wheels of an axle when making a turn or over uneven surfaces.

Driveline – Components used to propel the vehicle driveshaft and universal joints, transmitting torque from transmission to drive axle (same as drivetrain).

Driven Clutch – Member that is used to provide torque to another member, such as to the side gear. Each NoSPIN differential has two driven clutches.

Drivetrain – A series of components which transmit power from the engine to the wheels/tires (i.e., transmission, propeller shafts, transfer case, axle, differential, shafts, etc).

Double Reduction – Dual gear reduction used in rear axles.

Fishtailing – Side slipping of the vehicle caused by traction instability.

G.C.W. – Gross Combination Weight. G.V.W. plus vehicle weight and payload of towed vehicle.

G.V.W. – Gross Vehicle Weight. Total weight of vehicle and payload.

Gear Support Case - Case used to support the differential. Same as case assembly.

Ground Coefficient – The horizontal force required to move a body, divided by the weight of the body. The amount of friction at the ground; the "quality" of the ground surface (e.g., ice, snow, dirt, etc.)

Helical – "Angled" gear tooth form.

Holdout Ring – Ring which assembles to NoSPIN differential clutch; maintains clutch disengagement in a turning mode.

Indexing – A passing of one member over another, causing a slight audible sound from their contact (usually associated with the NoSPIN differential).

Input Torque – Measurement of available power.

Lead Ratio – On unequal wheeled four wheel drive tractors the transmission is so geared that any difference in road speed of the two axles results in a faster speed for the front wheels (lead or overrun), this prevents the front wheels from being pushed.

Limited-Slip Differential – A differential which utilizes some means of partially reducing, but not totally eliminating, individual wheel spin (e.g. clutches, springs, biasing pinion gears, etc.).

Locking Differential – A differential that provides a locked axle condition. Can be manual or automatic, as in hydraulic locking differential or NoSPIN differential.

Machined Splines – Splines that have been manufacturer by shaping, hobbing, broaching, or slotting.

NoSPIN Differential – Trademark of automatic, positive locking differential. Manufactured by Tractech.

Overrun Ratio - On unequal wheeled four wheel drive tractors the transmission is so geared that any difference in road speed of the two axles results in a faster speed for the front wheels (lead or overrun), this prevents the front wheels from being pushed.

Parallel Splines – Series of parallel keys cut along the axle shaft which mate with corresponding slots in the differential side gear.

Payload – Actual weight of useful cargo carried by vehicle.

Pinion (Input) Gear – The gear that is directly connected to the driveshaft which propels the differential and ring gear and provides power to the axle.

Planetary Axle – Axle having a gearset arrangement in a concentric pattern; consisting of a sun gear surrounded by pinion gears which mesh with an annulus ring gear. This gearset provides torque multiplication in a reduced area on the same center line as the axle shaft usually located on the hub ends of axle.

Pre-Load – Differential bearing adjustment achieved by adding or subtracting shims.

R.P.M. – Revolutions Per Minute. Term used to define rotation.

Ring Gear – The gear that is attached to the differential case and driven by the pinion gear.

Rolled Splines – Splines that are manufactured by the use of rolling dies to form the spline configuration.

Shims – "Spacer" used to achieve differential bearing adjustment.

Side Gear – The gear that is mounted in the differential case; has the axle shaft splined to it; driven by the pinion gear.

Single Speed – Axle or transfer case having a single gear ratio.

Shockload - A force caused by sudden impact.

Spider – The "center piece" of a standard, clutch-pack or NoSPIN differential; having a spider-like shape.

Spider Cross – Two or four armed member used to mount the standard differential pinion gears.

Spider Gear(s) – Bevel pinion gears that are mounted on spider cross that drive the side gears of standard or clutch type differentials.

Splines – "Teeth" on axles that mate with "teeth" (splines) on differential side gear.

Snap Ring – A circular expandable ring that is used to retain two members together, as a snap ring in a NoSPIN differential that retains the spider and center cam.

Standard Differential – Open or conventional differential with no means of traction control.

Tag Axle (Tandem) – Non-powered rear axle which follows drive axle. Provides additional load-carrying capacity and distribution.

Tapered Splines – Cone shaped spline configuration.

Thrust Blocks – Support mechanism used to prevent ring and pinion gear deflection.

Thrust Washer – Used in conventional differential to reduce wear to the support case.

Torque – Force having a twisting or turning effect. Also used in conjunction with the term "power".

Trunnion – Journals allowing pivoting or turning, such as on a spider cross. On a NoSPIN differential, the arm (there are four) which supports the differential in the case assembly.

Two-speed – Axle or transfer case having two selective gear ratios.

Understeer – The condition of steering when making a turn that causes the vehicle to go straight rather than turn freely.

Wheelbase – Distance between center lines of front and rear axles or to the center line of tandem axles.


This information is provided as a reference and is not meant to be a definitive source of information about lockers made by any manufacturer.  Use of this information is at your own risk.  This information may become obsolete over time.  No guarantee is made that it will be updated to reflect changes in products described. 

In other words, if you are going to make decisions about the care, use, installation, maintenance, purchase or diagnosis of locker problems, do not rely on this document - refer to the current, relevant documents produced by the manufacturer of your locker or differential device.

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