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Posted by: Buische Mar 9 2021, 09:34 PM

I used Dr. Evil's video suite to tear apart and rebuild my 901 transaxle. Super good, but no discussion about what to expect for proper diff case rotation torque without 1-5 gear stack installed. I pulled the diff and put it in a plastic bag, cleaned the case, and put new seals in. I did not think to check when disassembling.

Diff is open type, side gears spin fine inside diff case. But when I twist both hubs in the same directlon, it takes a lot of effort. I'm guess-timating 30 ft-lb. I don't think this makes sense, but I don't actually know. I am concerned that a previous owner installed the diff wrong. But, the bearings don't have damage that I can see, so I don't have other evidence pointing to incorrect build.

Any advice on how to tell if appropriate drag for bearings?

Thanks

Posted by: stownsen914 Mar 10 2021, 03:27 PM

I don't have the spec in front of me, but 30 ft lb is too high for sure (assuming it's just the diff in there, no pinion or mainshaft). It's usually measured in inch-lb (with only the diff carrier installed, no pinion or mainshaft). I recall for a 915 it's different depending on which brand of bearing you use, so it may be similar for the 901/914. If too tight, you remove shims from the diff carrier.

Edit - if you have the trans fully assembled including pinion + mainshaft assemblies, 30 ft-lb may be about right, though I've not measured it before to be honest.

Posted by: mgphoto Mar 10 2021, 03:35 PM

As per factory manual

Posted by: Buische Mar 11 2021, 01:21 PM

Very helpful info. Thanks.

Posted by: Buische Mar 11 2021, 01:23 PM

QUOTE(stownsen914 @ Mar 10 2021, 03:27 PM)

I don't have the spec in front of me, but 30 ft lb is too high for sure (assuming it's just the diff in there, no pinion or mainshaft). It's usually measured in inch-lb (with only the diff carrier installed, no pinion or mainshaft). I recall for a 915 it's different depending on which brand of bearing you use, so it may be similar for the 901/914. If too tight, you remove shims from the diff carrier.

Edit - if you have the trans fully assembled including pinion + mainshaft assemblies, 30 ft-lb may be about right, though I've not measured it before to be honest.

I initially had the 1-5 gearset and pinion installed, but took those out to be sure it wasn't due to interference with the pinion. There was some gray area in selecting intermediate plate gasket thickness, so wanted to be sure that was not a factor.

Posted by: Buische Mar 13 2021, 08:13 AM

Good news. Went out and put my clicker torque wrench on it, and a short bar across two bolts on the other side. Diff turned with just the weight of the torque wrench, so I think it's OK. The calibration on my hand and arm torque wrench apparently is way out of spec.

Thanks for the info, it helped me make what I think is a good call to continue the build.

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