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Well, after all of the front diff questions, I figured that I would post an update now that the work is done and the transmission is back in the car.


The end result is that the forward pinion bearings (at front diff end of pinion shaft) were shot. This was confirmed when I got the bad pinion out of the transmission and spun it in hand. The sounds that the bearings (or at least one of them, anyway) made while turning were definitely not good. Kind of dry and crunchy.


The ring and pinion gears were not damaged.


Mostly because of time (needing the car back as fast as possible), and partly because of money (the bearings were priced at $45 each), I decided to swap the front diff and pinion with known good parts from the junkyard transmission that I bought to fix this problem in the first place. That transmission was shot, anyway....drove great for about 36 miles and then the torque coverter shaft (the larger shaft that goes over the smaller, longer shaft) broke. Good for nothing but parts at that point.


On the whole, the operation was a success. The car is running and driving again, and is not making that piercing, obnoxious whirring whine anymore (happened under load). For anybody who has never done this before or is researching due to the same problem, here is the brief version of the repair:


1. Remove the transmission from the car. (A long procedure in itself)

2. Remove the torque converter from the transmission.

3. Remove the 14mm nuts and bolts from the front differential housing.

4. Separate the front differential housing from the transmission.

5. Remove the four 14mm pinion flange bolts from the pinion flange.

6. Remove the 12mm tailshaft housing bolts.

7. Remove the tailshaft housing from the transmission. (Be careful with the clutch pack and the steel gasket---especially the steel gasket)

8. Remove the large nut and washer from the pinion shaft.

9. Using a block of wood or a punch, drive the pinion shaft out of the reduction gear with a hammer.

10. Pull the pinion and the pinion flange shim out of the transmission from the front of the transmission.

11. Repeat steps 2 through 7 on the donor transmission.

12. Note the position of the large pinion shaft nut and mark the position of the nut to the shaft.

13. Repeat steps 8 through 10 on the donor transmission.

14. Install donor pinion shaft, with donor flange shim, to the original transmission. Seat firmly into the reduction gear at the rear of the transmission.

15. Loosely install the four 14mm pinion flange bolts.

16. Install the large pinion nut and washer to the pinion shaft at the reduction gear. Tighten nut to the marked position.

17. Tighten the four 14mm pinion flange bolts.

18. Reinstall the original tailshaft with 12mm bolts.

19. Install donor front differential case with 14mm bolts and nuts.

20. Reinstall the original torque converter.

21. Reinstall the transmission into the car.


It probably wouldn't hurt to check the gear lash after everything is bolted back in place. Because of micro-differences between casings, new sealants, or margin of error, there may be enough of a difference between the old parts and the "new" ones to upset the lash.

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Swapping the pinion shim over would rely on ther cases being machined exactly the same else the pinion depth would be wrong.

The lash is set with the adjusters on the outside of the trans where the axles go in.


I think.


Maybe he got lucky...

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I talked to him offline - car is at 223,000 miles and running great.  I'm going to attempt the exact same thing on my H6. 


There is also a pinion depth that needs set as well I think...but I'm going to hope I can keep that close enough be swapping the same parts/shims and hope the cases and thickness of sealants used all work out close enough.


I'll try to "check" backlash once I'm done assembling but I really have no idea how to do it and it sounds like too much of an art to me.

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The shim he was talking about I think is what sets the depth.


The backlash is important and requires a dial gauge- but if you used the same pumpkin you could just count how many turns the adjusters rotate, perhaps.

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