Rear Main Seal Replacement

[micah3639]

Hello Nissan Pathfinder Community!

 

I am the proud 4th owner of a 1991 SE-V6 with an auto transmission with only 85k miles.

 

The truck was incredibly well maintained by the previous owner.

 

The only issue with her is that there is a slow rear main leak. I got a few quotes from shops near me but my friend and I have decided to tackle it ourselves.

 

That being said, I want to get this post out there and pick all of your brains about this job, especially those of you who have done it before!

 

1. I already picked up a transmission jack on facebook marketplace and we've got all the regular automotive tools... Are there any other unique or proprietary tools we will need? We've got the Haynes repair manual for the truck so we have a pretty good idea of the process for pulling the transmission and another friend of mine is doing a manual swap on his gen 1 so we were able to connect with him and pick his brain about pulling the auto and get a visual on his Pathfinder with the transmission out which was really helpful.
2. OEM Nissan rear main seal part number appears to be 12279-AD205. (12279-AD205 - Seal 1984-2010 Nissan | Official Nissan Parts Store) Can anyone confirm this is correct and are there any other parts we will need for this job specifically?
   1. Would you recommend an OEM seal or has anyone had luck with aftermarket parts on Ebay or elsewhere? There appears to be some complete kits out there with other components. By the looks of it, the seal itself and then the triangular shaped paper gasket for the top of the bell housing:
      1. Victor Reinz JV538 Engine Rear Main Seal & Gasket Set for Z32 300ZX 12279-AD205 | eBay
      2. Fel-pro BS40628 Engine Crankshaft Rear Main Gasket Seal Kit | eBay
3. While we have the transmission pulled, what other components should we swap that will be easily accessible or require minimal extra work to replace, specifically wear components or other seals/gaskets? We've got all of labor day weekend set aside for this so the more we can knock out in one transmission removal, the better.
4. While the transmission is out, we are planning to put a cooler in since we will be draining the fluid and disconnecting the lines...which ATF cooler kit would you recommend and what ATF fluid should we put in? 
5. Any tips, tricks, or recommendations for tackling this? Any other helpful notes, pictures, or information you can lend?

 

Thanks in advance and looking forward to everyone's input!

Edited July 14 by micah3639
added pic of my pathy for those who didn't see my welcome post!!

[Slartibartfast]

 

My RMS needs doing too! It used to be a slow leak.

 

1. No special tools needed AFAIK. You can get the '90 factory service manual from cardiagn.com. The AT section has step-by-step instructions for dropping the tranny (AT-124), and the EM section has the same for doing the rear main (EM-20).

 

2. The gasket in the aftermarket kits goes between the retainer plate (which holds the seal) and the back of the engine block. Unless you're going to try and fish the seal out without removing the retainer, you'll need the gasket as well. I think I've got the Fel-Pro kit on the shelf for mine, don't remember--and of course I can't vouch for it as I haven't installed it yet.

 

3. I assume you'll need the gaskets for the exhaust crossover as well. You may need hardware or more depending on how much the exhaust fights you on its way out. These also tend to break exhaust studs (holding the manifold to the head), though I don't know that having the trans out would make these any easier to access. I would check breather hoses and exhaust hangers while you're under there. Might as well change the fluid in the transfer case too.

 

4. The trans cooler is a good idea. There are a few old threads on here with size and type suggestions. I don't actually know what mine's rated for, I got it secondhand and it's not marked. I installed mine in series with the existing cooler in the rad, and also added a Magnefine external filter while I was at it.

 

If you just drain and fill, you don't get the old fluid out of the torque converter, so I did a flush through the cooler lines instead. Take the lines off the existing cooler, put them in a bucket, run the engine until fluid stops coming out, add that much fresh fluid to the transmission, do it again, repeat until what comes out looks more or less like what goes in.

 

The trans fluid level is a bit of a pain to set. It has to be warmed up when you check it. If you set it cold, it'll be too high once it warms up. Either measure what you take out and what you put in and make sure they're the same, or undershoot a little so you have room to top it up once it's warm and you can check it properly. I thought mine was underfilled, warmed it up, and had to drain a bit back out of it.

 

The manual calls for Nissan-Matic D, which is still available. From what I've read, it's basically just Dexron III, so I used generic parts-store-brand Dex-Merc, which was cheap and available locally.

 

5. Torsion bars are also a pain to set up. If you have to drop the bars (and the service manual suggests you will), mark, measure, or at least take a picture of where the adjusters are set and how the bars are clocked vs the adjusters. Otherwise you'll be screwing around for a while trying to get your ride height back where it was. I used spray paint to mark the adjusters on a friend's S10 Blazer when we swapped the trans, and reassembly was as simple as matching up the paint marks. 

 

This thread recommends filling the gap between the RMS retainer and the pan with silicone to stop mud from getting in there and causing corrosion. Seems like a good idea.

 

Good luck! 

[micah3639]

Additionally- since the torsion bars are needing to be pulled, we are going to do boots and clips. I would like to change all the front mounting bolts over to SS as well. Are there any other wear components on the torsion bars that should be swapped while they're out? 

 

Should the rear adjustment bolts be swapped with all new hardware (locking nut, jam nuts, pivot)?

 

The front bolt sizes according to AI are below: can anyone confirm these?

 

The Main Large Bolt (1 per side): Thread Size: M12 x 1.25 (Fine Thread) Length: 35mm long
Tool Size: 19mm socket/wrench
The Smaller Side Bolts (2 per side): Thread Size: M10 x 1.25 (Fine Thread) Length: 25mm long

Tool Size: 14mm socket/wrench

Edited July 15 by micah3639