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Rear pinion seal replacement?

6324 Views 11 Replies 5 Participants Last post by  turbo8765
Hey fellas. I'm in the middle of swappin a 4-bolt rear into my 91' GSX, when I notice that the rear pinion seal needs to be replace on the thing first. I looked through my haynes manual, and it talks of how to do the replacement with the rear installed already(of course). I'm wondering how it could be done with the rear uninstalled like I have it right now. Is it even possible? The manual talks of checking the backlash on the rear, and adjusting it by removing/installing smaller/bigger shims. Thanks for any help guys.

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Bump. Come on....all of you early 1G guys that have done this swap should be able to help this guy out. :)
Almost 28,000 members, and no one has ever done a pinion seal replacement on their 3 or 4-bolt rear? Please, does anyone have any suggestions? I'd like to either get it in this weekend, or accomplish something else on the car. Thank you

It looks like all you will have to do is remove the driveshaft, use a large impact on the flange nut and pull the seal with a seal puller/pliers. I have a spare broken 4 bolt but I never did pull the companion flange off of the pinion gear shaft. I'm planning on putting a new ring and pinion in it when I hit the lottery/retire :p I took some pics too:

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Thanks for the reply terrible. The only thing I'm really concerned about is the whole adding/removing bigger shims. i've just never had to calibrate the backlash/what not, and I'm looking to see if anyone can help me on that. If there too much you're suppose to do this, and if it's not enough, then you have to do this, etc, etc. I just don't know how to go about calibrating it. Any help on this part would be helpful. It was explained in the haynes manual, but I don't have enough time right now to type up what it says. According to the book though, this whole backlash adjustment should be made when the rear is installed on the car, which it isn't right now. Thanks again.

Well mitsubishi uses whats called a crush washer inside the rear diff. From what I understand it is what sets the preload on the gears and sets the gear mesh in conjuction with the spacers. I'd call a machine shop and ask if they are familiar with it and I'm sure they would explain it alot better. It sounds to me like you might be replacing the ring and pinion too?
Before you undo the nut centre punch mark it to the pinion gear!!!! then undo it might have to use a small puller to get the flange off (sometimes) then replace the seal refit the flange and do the nut back up to the position that it was before. Its easy to do and you do not require to play with shims or backlash adjt' if you do it this way. i have done heaps like this and no problems. you can even do it up a touch further so the marks "just" misalign this is just bearing preload adjt'
I'm just replacing the seal, not the pinion. But you would still suggest that I replace that crush washer? I don't recall reading anything about it in the Haynes manual. They just suggested about maybe having to install different sized shims. Any more advice is appreciated.

As I said I wanted to rebuild the original I had in mine but it was over 1k just in parts. The ring and pinion where about 700$ and the rest of the parts are over 300$. With other rear ends you can get what's called a master install kit for under 150$ in most cases. With the mitsubishi it is a proprietary part so they have it exlusive to these cars witch means you pay the price when it comes to replacment parts.

As for the crush washer that is what I was told by a local import tech about most awd import cars. This might not hold true for these ones (dsm's) but maybe for things like a subaru?
Nat01 read what i have i put in. PM me if you want more info!
PM has been sent. Thank you

You don't need to do anything with the shims or the crush washer to replace the pinion seal. As a matter of fact, I wouldn't reccomend messing with the shims or the crush washer, it is difficult and requires precision tools to get the specs right. Just pull the flange as noted above and replace the seal and put the flange back.

The purpose of the shims is to set the correct pinion depth, sometimes reffered to as the checking distance. This is the distance from the centerline of the ring gear to the end of the pinion gear. You would need to set this if you were rebuilding the diff or changing the ring and pinion. You don't need to mess with any of this to change the seal. In terms of AWD imports and crush washers, I don't know of any rear end that dosen't use a crush washer import, domestic, awd or rwd. As stated above, the crush washer is used to preload the bearings for the ring gear. Hope this helps...

You can learn a lot about rear diffs by reading some of the off-road 4x4 sites, and, of course, the moosetang and camaro sites. All rear diffs use pretty much the same basic set-up.
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