Front Drive Axle - Limited Slip Differential Service
Article No. 85-13-13AXLE - FRONT DRIVING - LIMITED SLIP DIFFERENTIAL SERVICE INFORMATION
LIGHT TRUCK 1984-85 BRONCO II, RANGER (4x4)
When the 1984-85 Ranger/Bronco II Shop Manuals were published, information covering the servicing of the Limited Slip Dana Model 28 Front Driving Axle was inadvertently omitted.
The following information is required for servicing and repairing of 1984-85 Ranger/Bronco II vehicles equipped with Limited Slip front driving axles:
1. Remove the front driving axle assembly from the vehicle as outlined in Section 15-35 of the shop manual.
2. Disassemble the front axle assembly removing the carrier assembly as outlined in Section 15-35 under "Carrier Disassembly". Disassemble the carrier assembly as outlined below.
Figure 11:
Figure 12:
DESCRIPTION AND OPERATION:
The two pinion limited-slip Dana Trac-Lok Model 28 front axle (Figure 11) has a power flow identical to a conventional rear axle, plus a more direct power flow which automatically takes effect as driving conditions demand. This more direct power flow is from the differential case to each axle shaft through clutches (Figure 12).
A conventional differential transmits all of the ring gear torque through the differential gears to the axle shafts. Torque is at all times equal on the axle shafts, and if one wheel slips, the other wheel can only put out as much torque as the slipping wheel. The limited-slip differential is similar, except that part of the torque from the ring gear is transmitted through clutch packs between the side gears and differential case.
Figure 24:
Figure 25:
The multiple disc clutches with radial grooves on the plates and concentric grooves on the discs are engaged by a preload from dished springs, plus separating forces from the side gears, as torque is applied through the ring gear (Figures 24 & 25).
Each clutch plate and disc pack consists of steel plates, set between the case and the side gear. The clutch plates, having external lugs, are locked to the differential case by the external lugs. The clutch plate that is installed next to the case is a Belleville spring plate. This plate is installed with the concave (dished) side against the case. The remaining clutch discs have internal spline teeth which lock to the splined hub on the side gear. The side gear is, in turn, splined to the axle shaft and acts as a pressure plate against the clutch pack. Since the side gear fits against the pinions on the cross shaft (mate shaft), any outward force exerted by the cross shaft and its pinions will press the side gear against the clutch pack and thus connect the differential case directly to the axle shaft.
The limited-slip differential prevents momentary spinning of one of the wheels when it leaves the road because of a bump, or encounters poor traction because of a slippery road. Under these conditions, even though the traction load is relieved on the one wheel, the acceleration load is simultaneously applied to the differential case as the engine tries to spin the wheel.
When the axle is in a turn, the appropriate clutch releases automatically to allow normal differential operation as required. In the straight-ahead position, the differential case is driving both wheels and thus applies an equal load against both axle shafts. On a turn, however, the outside wheel turns faster than the inside wheel. The outside wheel instead of being driven by the case, now tends to drive the case. With the power thus relieved, the differential case releases its load against the outside wheel axle shaft which, in turn, releases its pressure against the outside wheel clutch pack. With the clutch released, normal differential action will take effect.
For a complete understanding of limited-slip operation, it is important to recognize two things:
1. If with equal traction, both wheels slip, the axle has done all it can do.
2. In extreme cases of differences of traction, the wheel with the least traction may spin after the axle has transferred as much torque as possible to the non-slipping wheel.
DIAGNOSIS AND TESTING
If noises or roughness, such as chatter are present in turning corners, the probable cause is incorrect or contaminated lubricant.
Before any differential is removed and disassembled for chatter complaints, the correctness of lubricant should be determined.
Refill the front driving axle with the specified quantity 0.50 liters (17 ounces) of Hypoid Gear Lubricant, C6AZ- 19580-E (ESW-M2C105-A) or equivalent and add 0.015L (0.5 ounce) of Friction Modifier Additive C8AZ- 19B546-A (EST-M2C118-A) or equivalent to the front drive axle. Warm the axle up and recheck for chatter by making a minimum of ten figure-eight type turns.
If this is unsuccessful, a complete lubricant drain, flush and refill will usually correct chatter. The following procedure is recommended to ensure that the system is flushed of old lubricant.
1. Warm the lubricant by vehicle road operation or five minutes of operation in gear with both front and rear wheels off the ground on a hoist.
CAUTION: Never place the transmission in gear with the engine running when only one wheel of a limited slip differential equipped vehicle is raised. The vehicle might drive itself off the jack and cause damage or injury.
2. Drain the lubricant while warm. Remove the drain plug and using a suction pump, remove the lubricant.
3. Refill the axle with a specified lubricant. Install and tighten the drain plug.
4. Operate the vehicle for approximately 16 Km (10 miles), making at least ten figure eight turns to flush the old lubricant out of the clutch packs.
5. Repeat Steps 2 and 3 and drain and refill the front drive axle.
6. It is possible that a slight chatter, requiring additional vehicle operation may remain after Step 5. If chatter still persists after 160 Km (100 miles) of operation, or remains severe after Step 5 above, disassembly and repair will be necessary.
For further diagnostic and testing procedures refer to Section 15-01, General Driving Axle and Driveshaft Service and Section 15-35, Front Drive Axle.
REMOVAL AND INSTALLATION For Dana Models 28 Limited slip-differential front axle Removal and Installation procedures, refer to Section 15-35, Front Driving Axle, for differential case removal and installation procedures.
Figure 11:
DISASSEMBLY AND ASSEMBLY
Dana Limited-Slip Front Axle Refer to attached Figure 11.
The Dana Model 28 Front Driving Axle limited-slip differential assembly is removed and installed in exactly the same manner as the conventional differential assembly. For these service procedures refer to Section 15-35 - Front Drive Axle - Dana. Friction Modifier, C8AZ-19B546-A, EST-M2C118-A or equivalent friction modifier is the only authorized additive which may be used with this axle.
When axle lubricant has been drained for front axle repair (limited-slip only), refill the axle with the specified
quantity (17 oz.) of Hypoid Gear Lubricant, C6AZ- 19580-E (ESW-M2C105-A) or equivalent and add 0.5 ounce of Friction Modifier C8AZ-19B546-A (ESTM2C118-A) or equivalent.
Figure 11:
MODEL 28 - 2-PINION (DANA TRAC-LOK)
Refer to Figure 11.
DISASSEMBLY
The differential bearings need not be removed to overhaul the limited-slip differential.
CAUTION: When working on differential case assembly, be careful not to damage the differential bearings. To remove and install the side gears, washers, and clutch packs during disassembly and assembly requires special procedures and tools.
Figure 15 - DIFFERENTIAL PART NUMBER LOCATION:
The Trac-Lok is identified with a manufacturing date and complete part number stamped on the barrel of the case (Figure 15).
When referring to the Trac-Lok, it is recommended that the complete part number and build date be obtained. To do this, it will be necessary to wipe off the lubricant from the case.
For Model 28 use Limited Slip Differential TooI T83T-4205- A.
An axle shaft placed in a vise, with the splines extending above the jaws of the vise not more than three inches, makes an excellent holding fixture after the case has been removed from the housing.
Figure 13 - REMOVE RING GEAR ATTACHING BOLTS:
Figure 14 - REMOVING RING GEAR FROM CASE ASSEMBLY:
1. Place differential case assembly in a vise as shown in Figure 13 and remove ring gear bolts.
2. Remove differential case assembly from vise and remove ring gear as shown by tapping with a rawhide type hammer to free it from case. It will be necessary to remove the ring gear to allow clearance for the removal of the cross pin. (See Figure 14).
NOTE: It is recommended that whenever the ring gear bolts are removed, they be replaced with new ones.
Figure 16 - REMOVING CROSS-SHAFT LOCK PIN:
3. Place one of the axle shafts which was removed from the assembly into a vise. Tighten shaft in vise firmly. Caution should be used that the vise jaws do not locate on axle splines or any machined surfaces. Place the differential case assembly on the splined end of the axle shaft.
4. Drive out the lock pin retaining the cross shaft using a long punch. (See Figure 16).
Figure 17:
Figure 18:
5. Reposition the differential case into vise as shown. Remove the cross shaft from the case using a hammer and a large drift. (See Figure 17).
6. Position the Step Plate, T83T-4205-A4 into the bottom side gear (Figure 18). Apply grease to the centering hole of the Step Plate.
Figure 19:
7. Install the Forcing Nut T83T-4205-A2, and the Forcing Screw T83T-4205-A3, into the differential case. (Figure 19).
If replacement of one gear is required due to wear, etc., then both side gears, pinion mate gears, and washers are to be replaced.
Figure 16 - REMOVING CROSS-SHAFT LOCK PIN:
Figure 17:
8. Guide the forcing screw on to the step plate (Figure 16).
9. Tighten the forcing screw tightly. This will move the side gears away from the differential pinion gears, and relieve the normal loaded condition. Using a piece of 0.762mm (0.30 inch) thick shim or gauge stock, push out the differential spherical washers, (Figure 17).
10. Momentarily,loosen the forcing screw. This step is very important to relieve the pressure of the clutch pack.
11. Re-tighten the forcing screw until a very slight movement of the differential pinion gears is seen.
Figure 18:
Figure 19:
12. Insert Handle, T83T-4205-Al into the pinion mate shaft bore and rotate the case (Figure 18). Continue this until the differential pinion gears can be removed through the large openings in the case. When attempting to rotate the side gear, some tightening or loosening of the forcing screw will probably be required to permit the gear movement.
13. Retain the top side gear and clutch pack in the case with the hand and remove the forcing screw. Continue to hold the side gear and clutch pack and remove the gear rotating tool (Figure 19). Remove the top side gear and clutch pack. Keep the stack of plates and discs in exact order.
14. Turn the case so the flange, or ring gear is up. As this is done, ease the step plate, side gear and clutch pack out of the case.
Figure 20 - GUIDING FORCING SCREW INTO STEP PLATE:
Figure 21 - REMOVING SPHERICAL WASHERS:
15. Remove the retainer clips from both clutch packs to allow separation of the discs and plates for cleaning and inspection. BE SURE TO KEEP THEM IN THE EXACT ORDER AS REMOVED. (Figure 20.).
- Inspect all parts for wear, scoring, etc.
- Plates and discs. lf any one member of either stack shows evidence of excessive wear or scoring, the complete stack is to be replaced on both sides, Figure 21 shows normal grooving of a plate and a disc.
- Side gears and pinion mate gears:
The gear teeth of these parts should be checked for extreme wear and possible cracks. The external teeth of the side gear, which retain the concentric groove discs, should also be checked for wear or cracks.
- Cross shaft. If excessive wear is evident, the cross shaft should be replaced.
- Clutch retainer clips. If wear is evident on any one of the retainer clips, all four clips must be replaced.
- Differential case. If scoring, wear, or metal pickup is evident on the machined surfaces, then replacement of the case if necessary.
Figure 24:
ASSEMBLY
1. Install the side gears and thrust washers. To do this, whether the original plates and discs or new ones are used, assemble them in exactly the same order as the originals. (Refer to Figure 24). Refer back to illustrations used during disassembly for guidance in subsequent re-assembly operations.
2. Prelubricate the thrust face of the side gear and assemble the plates and discs to the side gear splines, prelubricating each part with Hypoid Gear Lubricant C6AZ-19580-E(ESW-M2Cl05-A) or equivalent or with Friction Modifier C8AZ-19B546-A (EST-M2C118-A) or equivalent lubricant, both stacks.
3. Assemble the retainer clips to the ears of the plates. Make sure both clips are completely assembled or seated onto the ears of the plates.
Figure 19:
With the differential case positioned as shown in Figure 19, assemble the clutch pack and side gear into the case. Make sure the clutch pack stays assembled to the side gear splines, and that the retainer clips are completely seated into the pockets of the case. To prevent the pack from falling out of the case, hold them in place by hand while re-positioning the case on a bench.
4. Assemble the step plate into the side gear. Apply a small amount of grease, Multi-Purpose Long-Life Lubricant, C1AZ-19590-B(ESA-MMC75-B)or equivalent into the centering hole of the step plate.
5. Assemble the other clutch pack and side gear. Make sure the clutch pack stays assembled to the side gear splines, and that the retainer clips are completely seated into the pockets of the case. Install Step Plate, T83T-4205-A4 on top of the side gear.
6. Hold the side gear and Step Plate T83T-4205-A4 in position by hand. Insert the Forcing Screw T83T- 4205-A3 down through the top of the case so it is piloted in the side gear and thread Forcing Nut, T83T-4205-A2 on the screw. The tip of the Forcing Screw must contact the Step Plate.
7. With tools assembled to the case, position the case onto the axle shaft (as a holding fixture) by aligning the splines of the side gear with those of the shaft.
8. Position both differential pinion gears opposite one another through the openings in the case. Be sure the holes of the gears are lined up with each other. Hold the gears in place by hand.
Tighten the forcing screw so that the side gears will move away from the differential pinion gears and relieve the loaded condition.
Figure 23 - HOLDING CLUTCH PACK TO REMOVE TOOLS:
Assemble washers into the case. Use a very small screwdriver to push the washers into place. Be sure the holes of the washers and gears are lined up exactly with those of the case. Remove the forcing screw, forcing nut, handle, and step plate.
Figure 22:
9. While holding the differential pinion gears in place, insert the Handle (T83T-4205-A1) into the pinion mate shaft. Pull on the handle so that the case will rotate and allow the differential pinion gears to rotate and enter into the case.
As mentioned under Disassembly, it will probably be necessary to adjust the forcing screw by very slightly loosening or tightening it until the required load is applied to allow the side gear and differential pinion gears to rotate.
10. Rotate the case until the holes of both differential pinion gears are lined up exactly with those of the case.
Prelubricate both sides of the pinion spherical washers with the specified lubricant, Hypoid Gear Lubricant C6AZ-19580-E (ESW-M2C105-A) or equivalent.
11. Apply torque to the forcing screw to allow clearance to assemble the spherical washers.
CAUTION: DO NOT OVERTIGHTEN THE FORCING SCREW. OVERTIGHTENING THE FORCING SCREW MAY DAMAGE THE CLUTCH PLATE AND DISC ASSEMBLIES.
Install the cross shaft in the differential case. Install the cross shaft roll pin.
12. Install the ring gear on the differential case, and tighten the attaching bolts to specification. Refer to Specifications in Section 15-35 Dana Model 28 Front Driving Axle.
OTHER APPLICABLE ARTICLES: None
WARRANTY STATUS: "INFORMATION ONLY"