8-3/4 742 Gear Noise? Other Problems

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Aaron

Aaron

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I bought what was suppose to be a rebuilt 742 case 8-3/4 third member. Suppose to have new bearings, rebuilt clutch suregrip and new yukon 3.55 gears. The seller said he bought it rebuilt and it sat for a year and never used it, then sold it to me.

Anyways, I bolted it in this weekend, right away I get a few drips from the pinion seal area after filling the rear with Royal Purple 75-90 Max-Gear. I thought little of it (dry seal maybe) and drove the car for five minutes, right away I notice gear noise but only on deceleration/coasting. Is this normal? After I get back I notice lots of gear oil has been lost via the pinion seal area (it was on the exhaust even). Also the SG was chattering when I went around corners at low speeds on the way back, is this normal (I think I lost about a half quart)? Do you have to pre-lube the SG, our will it get enough lube from filling the rear? Is it a royal pain to replace the pinion seal and yoke? Whats the best at-home method? And gotchas?

So, I plan to remove the third-member next, and check the gear pattern, do I have to check the pattern under load, or just spin the yoke a couple times?

Also, should I just try to return it for a refund (internet purchase), or are these simple problems that can be remedied?
 
I think I am just going to try to return it for a refund. There is alot of play in the yoke/pinion, I can move it up and down side to side by hand. This cannot be a good thing?
 
Hi Aaron,

With the pinion/yoke loose like that, that's more than likely the cause of the noise. That needs to be fixed, as something is not quite right there. The 742 casting uses shims to determine pinion bearing preload. Quite possibly it was not setup right in that area, or the pinion nut has come loose.

I don't know what recourse you have except to fix it yourself correctly, and chalk it up as a 'live and learn' deal.

Call me anytime at the shop if you need help setting that rear up correctly. 303.660.0522.

Chris
 
I got the third-member out of my Duster, the pinion bearing near the ring gear is loose in the race. I can move it a little forward back side to side just by moving the yoke up and down. It looks like the nut for the yoke is not torqued enough, as there is no thread from the pinion showing (about flush with the nut). I assume this is why I also had the pinion leak (with what he says is a new seal), as the pinion isnt tight in the case. Would tightening the nut be the right next step?
 
It appears the pinion nut is to spec on the yoke. Do the front pinion bearings go bad easily? I suspect the yoke may have hit the inside on the shipping crate at some point possibly.
 
Additional question? Do all cases (489,742,741) share the same "front" pinion bearing? I know the rear bearings vary in the different third-member cases.
 
Some searching on Rockauto.com shows that indeed the 742 case uses a different front bearing than the 741 and most likely the 489.
 
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