Can I replace diff rear cover gasket without dropping the diff?

[kaibiagi]

Pretty much asking what the title is saying. Haven't been able to find this info in my searches so thought I'd ask here. Looks like I've got a fluid leak from my rear diff because it's all oily and there is a little puddle on the ground. I'll attach a picture, just in case anyone else has an idea of where it could be leaking from other than the rear seal. Thanks for the help!IMG_6577.pdf

[bunkhouse]

 Is there any oil forward under the pinion seal?

[kaibiagi]

I can't see any, but I haven't gotten the car jacked up yet so this is just a ground view. I won't know for sure until my new jack comes in and I can lift it up.

[jhm]

To answer your original question…no, you really can’t.  You didn’t state which diff you have; but assuming it’s an R180 or R200, the rear cover is an integral component of the differential mounting.  Even assuming you could hold the diff in place with a jack while you try to remove the mustache bar and rear transverse link, it’s just not practical to do it that way.

 

Do you have the FSM for your car?  If not, you can download them free at:  http://www.xenonzcar.com/s30/fsm.html

 

Hope this helps.

[AydinZ71]

What John said. To be more specific (because I have done this many, many times *headslap*), the mustache bar is in the way. The mustache bar can  only be removed by lowering it off the body bolts (which behave like a stud since they hang from the unibody). The diff cover has studs that link it to the mustache bar. The diff and bar are blocked form dropping because of the lower control arm crossmember.

 

So, if you wanted to try and change the rear cover without removing the diff, here is what you would need to do.

 

1) support the weight of the diff with a jack.

2) remove fastening nut on front diff mount so the diff can pivot

2a) possible need to detach the driveshaft if it keeps the diff from pivoting rearwards

3) remove lower rear control arm crossmember

4) unbolt mustache bar

5) angle the riff downwards when viewing the cover, balancing the diff on the jack and keeping it from falling off the jack. 

6) once mustache bar 14mm bolts are cleared, remove mustache bar from diff (M12 studs). 

7) remove diff cover.

 

but by then, you basically have demounted the diff for all intents and purposes but its just hanging off the front mount and supported by a jack. Now be careful while you scrape the old gasket material, not to have the diff roll off the jack. 

[kaibiagi]

Thanks for the info everyone, this has been helpful. I do have an R200, and it looks like it's just not very feasible to try and do this without dropping the diff, so I might just end up doing that.

[AydinZ71]

You can remove the diff cover studs and replace them with bolts. That way, you can replace the gasket in the future without dropping the diff. Only downside is they went with studs for the inherent safety they provide. If the nuts come loose on the stud, the diff doesn’t go anywhere. You will need to be disciplined in torquing the bolts correctly and using loctite if you ditch the studs. A steel bolt threaded into a cast aluminum diff cover is not really risky, but because of the dissimilar metals, they can lose torque over time from vibration and heat cycling on the cover. 

Edited September 25, 2023 by AydinZ71