It's been on the project list for awhile but finally done! The donor is a diff from a 635CSi which is a 3.73 LSD with the ZF unit. Set me back $200. I REM polished the bearings, races and R&P.
Tools
- 36 mm socket (2 makes life easier)
- in/lb beam torque wrench
- 3/8" to 1/4 adaptor
- 1/2" to 3/8 adaptor
- flange holder for input flange (make one)
- flange holder for carrier flange (to measure carrier preload)
- gear marking compound or daiper rash cream
- dial indicator w/ base
- heavy duty impact or long breaker bar
- large bearing separator
- bearing race installation kit (harbor freight)
- chisel/punch
all other tools should be standard stuff
Assembling the LSD carrier. Notice the stock 45/45 ramps.
1. Set carrier preload with the pinion NOT in the case. Install the LSD carrier and side flanges then take a measurement. I got 10 in/lbs. Remove LSD carrier
2. Install races into case. Pinion shim goes under inner race.
3. Install pinion and get pinion snugged so there is no up and down play in the flange but no drag (don't crush the crush sleeve yet). Do NOT install input seal.
4. Reinstall LSD carrier
5. Check backlash and gear pattern. I got .0045" backlash and the gear pattern is below. I think if you reuse the shims that come with the case then it should be pretty close.
6. Once gear pattern and backlash are good, then onto setting pinion preload. Remove LSD unit.
7. Install a holder onto input flange. Made one from a long piece of angle steel with holes drilled into it.
8. Take out slack in the flange. Then give a short blast with an impact, remove holder and check preload. Repeat. Go SLOWLY! I got 16 in/lbs. Or you can use a long breaker bar.
I filled it and went to a weekend at the track. 8 20 min sessions, Tried not to slide the rear end a lot. Changed the oil after the event.
There was more understeer. I'd like to try 30/60 ramps to see if that helps. At first, the diff felt really tight, the back end chattered a couple of times when the rear tires were sliding. That went away or at least it didn't happen again. As the weekend went on, the rear tires were much more responsive than the OE diff. I would slide the tire rear tires on exit, have the steering wheel straight and could use the throttle to finish the turn and get the car straight. It was a lot easier with this ZF LSD than the OE diff.
The tech who replaced my input seal on my old diff over torqued it. It had more than 30 in/lb preload and you could barely turn it by hand. I got my new diff in and the car was faster.
Why a 3.73? With 275/40R17s, I'm close to redline on the straights at MSR Houston. Anything shorter will need a downshift. I can still achieve similar gearing as a 3.91 with 245/40R17s.
Tools
- 36 mm socket (2 makes life easier)
- in/lb beam torque wrench
- 3/8" to 1/4 adaptor
- 1/2" to 3/8 adaptor
- flange holder for input flange (make one)
- flange holder for carrier flange (to measure carrier preload)
- gear marking compound or daiper rash cream
- dial indicator w/ base
- heavy duty impact or long breaker bar
- large bearing separator
- bearing race installation kit (harbor freight)
- chisel/punch
all other tools should be standard stuff
Assembling the LSD carrier. Notice the stock 45/45 ramps.
1. Set carrier preload with the pinion NOT in the case. Install the LSD carrier and side flanges then take a measurement. I got 10 in/lbs. Remove LSD carrier
2. Install races into case. Pinion shim goes under inner race.
3. Install pinion and get pinion snugged so there is no up and down play in the flange but no drag (don't crush the crush sleeve yet). Do NOT install input seal.
4. Reinstall LSD carrier
5. Check backlash and gear pattern. I got .0045" backlash and the gear pattern is below. I think if you reuse the shims that come with the case then it should be pretty close.
6. Once gear pattern and backlash are good, then onto setting pinion preload. Remove LSD unit.
7. Install a holder onto input flange. Made one from a long piece of angle steel with holes drilled into it.
8. Take out slack in the flange. Then give a short blast with an impact, remove holder and check preload. Repeat. Go SLOWLY! I got 16 in/lbs. Or you can use a long breaker bar.
I filled it and went to a weekend at the track. 8 20 min sessions, Tried not to slide the rear end a lot. Changed the oil after the event.
There was more understeer. I'd like to try 30/60 ramps to see if that helps. At first, the diff felt really tight, the back end chattered a couple of times when the rear tires were sliding. That went away or at least it didn't happen again. As the weekend went on, the rear tires were much more responsive than the OE diff. I would slide the tire rear tires on exit, have the steering wheel straight and could use the throttle to finish the turn and get the car straight. It was a lot easier with this ZF LSD than the OE diff.
The tech who replaced my input seal on my old diff over torqued it. It had more than 30 in/lb preload and you could barely turn it by hand. I got my new diff in and the car was faster.
Why a 3.73? With 275/40R17s, I'm close to redline on the straights at MSR Houston. Anything shorter will need a downshift. I can still achieve similar gearing as a 3.91 with 245/40R17s.
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