Transmission Tear Out Lessons Learned and Questions/Advice

[gamellott]

I'm pulling the manual transmission in order to seal up the leaking 30yo seals between the rear main and the front transmission... among other things. Judging from the marred up Phillips head bolts, It's not the first time this has been done... 30 years and 300K miles... Clutches don't last that long. No surprise there. Bonus!! the carpet did not tear!!

 

As a part of prepping to pull, I pulled up the carpet and boot for the shifter. Under that, on the firewall, it appears as though there was a plastic shell in the well of where your feet go. That has fallen completely apart, and I had to resort to using a vacuum to clean it up. I don't recall anything being like that on my D21 when I last did something like this 15 years ago. Under the sound dampening material, there was a small piece of aluminum foil covered heat dissipating material. I know Nissan put it in there for a reason, but I didn't see any evidence of that actually getting hot. Does anyone know exactly how important that is?

 

Tomorrow... the work from underneath... mostly.... Oh fun... I hate working on exhaust!!!

[RF600]

If you have a 2x4 it’s much easier. 4x4 sucks. Pretty much have to take the front end apart. 
 

The trans are stupid heavy. Be careful and use a jack to support the trans. Strap it down so it doesn’t fall. 

[FirstGenFreak]

Either have to drop the front diff or remove the torsion bar crossmember. 

I'm older now, not struggling on my back anymore.
Last time I put mine in, I used an engine crane through the passenger door. 

[Slartibartfast]

I've done the engine-crane-through-the-door method on a Toyota. Worked great, but had me worried with how close to the windshield the boom ended up. I think I had a load leveller in between the crane and the trans, which was great for lining it up, but meant the boom sat higher than I would've liked. Might get more room to lift with the boom up against the trans.

 

The firewall in mine had the same fluff panel, with the same layer of crumbling black plasticky crap. I assume the black crap was once rubber of some variety. Mine came apart like peanut brittle. The fluff behind it was saturated with lung dart stink, so it was all bin-bound anyway. I put a little sound deadening in its place, probably should've done more. Might do that the next time I have the dash out.

 

I don't remember a foil bit. Where was that?

 

Good luck with the exhaust! I was pleasantly shocked when the exhaust fasteners on my parts car just came loose like they were supposed to. Hopefully yours are similarly cooperative.

[gamellott]

Spent the day trying to get all of the interference out. Turns out that it would have been easier if I dropped the front axle as @FirstGenFreak mentioned. Might do it when I go to put it back in. A lot of the bolts holding the transmission in were incredibly difficult to get to with the front differential there. At the end of the day today, I still have two bolts holding the transmission to the engine, They're on the top of the transmission. Not easy to get to... and I haven't been able to disconnect the Y-pipe from anything. Nuts are removed from the manifold, but nothing is budging there. The bolts holding the pipe together aren't moving, and if I have to get those off, it's probably with a saw. Saving it for another day when I have rested and the cuts on my hands have somewhat healed  

 

My 4 cylinder D21 was way easier to pull the transmission....

[gamellott]

@Slartibartfast The foil covered heat shield stuff was located at the top drivers side of the firewall. A section about 4" x 10" across the top. IIRC, the entire passenger side is covered. I didn't pull that side down because it wasn't falling apart like the drivers side. The drivers side is all metal now, where the passengers side still has the padding on the bulkhead. Both sides of the rubber/plastic stuff had fallen off. Something that I wasn't entirely expecting, or even know was there...

 

Found a couple instances of non-standard hardware, and one where it was clearly too short and stripped out on the transmission. Once I get it out, we'll see if I can address that and fix it with good threads. At least they didn't put it together with locktite 

 

Is it possible to pull the transmission without pulling the Y-pipe out? It looks like it might clear the pipe if I'm able to pull it straight back.... If.... 

[adamzan]

I've never seen any foil on any of my wd21s but only had 94 and 95 models. There is a black rubberized material that just falls apart on top of the padding, though.

 

Yes pulling the trans is a PITA... I've got to do it on mine soon as the RMS is leaking (must have installed it wrong) and the transmission is doing the classic whine in all gears but 4th.

 

I don't see how pulling the front diff would help getting it out as you can't get the transfer case part past the torsion bars crossmember. When I last did this on an auto truck I had to pull the Y pipe, a manual you might get away without doing it.

Edited April 6 by adamzan

[gamellott]

@adamzanThere are 2 bolts on the transmission that are about impossible to get to where the front pinion is at. I was able to remove them by fishing a wrench up there. I don't think I'll be able to get them back in without, at least, dropping it a little. One of the bolts on there was a non-standard bolt that was too short and stripped out of the bell housing. Something to investigate while it's out.... Maybe... while I'm at it... I could drop the oil pan and seal that back up... but it doesn't look like it's leaking at all from there....

 

Progress today; I cut the heads of the bolts off of the Y pipe and cut the pipe just in front of the catalytic converter. I had to fish the wire for the oxygen sensor out. I was able to unpin the connector and put the box end of a wrench around that. Took quite a bit of force to get it started, but it came out of the bung fairly easily once started.

 

Dropped the transmission with just enough room to clear the extension housing on the fixed crossmember behind it. Sooo... that answers my question to being able to pull the transmission without chopping out the Y-pipe. That would be a NO, unless you take off the transfer case.

 

Next: the rear main on the engine, end caps on the heads, front seal on the transmission and the intermediate seal between the transfer case and transmission.... Lots of stuff to do. New clutch, of course.

 

A lot of work for a little bit of oil and piece of mind I guess...

[adamzan]

It's a good time to replace the sump gasket that mates to the RMS housing as well. That's a common leak point. Once assembled I just filled the area with RTV lol. No leaks on that rig.

 

I know what you mean on those front bolts. Are you talking about the ones that go the opposite direction of the rest of the bell housing bolts? If so, those are a huge bitch lol.

[gamellott]

@adamzan You're probably correct. It wouldn't hurt too much to pull the pan since I've already got EVERTHING apart. Just have to pull the front axle/pinion if I'm going to do that. I imagine the bolts holding the CVs in place are super tight... Probably pretty easy now since I have everything else removed... 

 

Yes, the front bolts that are opposite everything else on the top of the bell-housing. I wish I had a donor with good hardware to rob off of so I could have it all the same. One of my OCD's I imagine. 

 

On a different note, Just put in an order for more, unexpected, parts. So, it's going to be a couple of weeks before I start trying to button this thing back up. I know everyone is on the edge of their seats wanting to read about me crushing myself under the transmission

[adamzan]

I think you can change the rear pan gasket without removing the pan. It attaches to the bottom of the thing the RMS sits in.

[Aonghus]

5 hours ago, adamzan said:

I think you can change the rear pan gasket without removing the pan. It attaches to the bottom of the thing the RMS sits in.

That's correct. It's a rubber seal that should come with the RMS kit, along with some RTV to seal the edges.

 

We recently went through all this with my son's '92. It was a bugger job than I anticipated and yeah some if those bolts are a royal pain! Easiest thing we found for the top bolts on the bell housing was stacking multiple extensions and reaching them from a couple feet back. A couple of the bolts were easiest to get to through the wheel wells.

 

Side note, and I wish we'd done this, it'll probably be easier to replace the trans oil while it's out so you can more easily tip it to the side to get the proper amount in. Unless you're has the fill plug at the correct height, the 92 does not.

Looking forward to an update!

[gamellott]

I think, if I'm going to go as far as replacing that bottom piece of rubber, I'll take out the whole oil pan. It took a decent amount of force with "Pry Tabs" to pull the front cover off of the transmission, I can only imagine how fun it would be to pull the RMS housing and not have ANYTHING to pry on.

 

As far as filling the transmission, mine is a 92 as well. I'm planning on filling it through the shifter before I button up the interior. About the easiest way if you're already pulled apart.

[rhino93]

Not tearing the carpet is an incredible feat! 

 

I've definitely pulled the manual trans out of my 93 without cutting/removing the Y-pipe, but I did have the torsion bar crossmember and front diff out. Was a bit of a puzzle to get the transfer case tail housing down past the fixed crossmember, but it is doable. Front diff is very annoying to get back in because of the weird balance, but torsion bars and crossmember are pretty easy, even if a few rusted bolts give out (as they did for me). For posterity's sake, pulling the Y-pipe down off the manifolds early is very nice. With that and the trans mount disconnected, the motor mounts allow quite a bit of forward/backward tilt which can make reaching those top bell housing bolts easier.

 

For install, I found it handy to cut the heads off a couple of spare bell housing bolts and thread them into the block. Definitely not necessary but helped a bit with aligning trans and engine. Also, since the engine can move so much it can be hard to eyeball the alignment. Having someone to watch from a wheel well while you wiggle and push is very nice. Not sure if any of this is helpful at all, but good luck!

Edited Monday at 06:24 PM by rhino93

[FirstGenFreak]

When removing your torsion bar X-member, measure the tail of the adjuster bolts , that way you can get your suspension pretty much where it was in height, then you only need a small fine tune if necessary.

[Slartibartfast]

2 hours ago, FirstGenFreak said:

When removing your torsion bar X-member, measure the tail of the adjuster bolts , that way you can get your suspension pretty much where it was in height, then you only need a small fine tune if necessary.

 

When I helped a friend swap the trans in his S10 Blazer, we just shot a spot of paint on each torsion bar adjuster. We used a different color on either side so we couldn't mix up the parts. Then when we put it back together, we just lined up the paint marks. Worked great.

[Aonghus]

On 4/10/2025 at 7:27 AM, gamellott said:

I think, if I'm going to go as far as replacing that bottom piece of rubber, I'll take out the whole oil pan. It took a decent amount of force with "Pry Tabs" to pull the front cover off of the transmission, I can only imagine how fun it would be to pull the RMS housing and not have ANYTHING to pry on.

 

As far as filling the transmission, mine is a 92 as well. I'm planning on filling it through the shifter before I button up the interior. About the easiest way if you're already pulled apart.

Just so I make sure I didn't lead you astray:

The rear rubber oil pan seal attaches to the aluminum RMS housing which can be removed from the block with 4 (I believe) bolts. If your oil pan gasket is leaking elsewhere of course you would want to remove the pan and replace the gasket but there's no need if it's just the curved rubber bit beneath the RMS housing.

[gamellott]

Good pointers on the torsion bars. Measuring thread protrusion is a good idea. Paint is also a good idea. I'm well past that point right now, but the bars are stuck in the crossmember right now, and I'm not sure if I really want to try to force them out. If I do, I might get some red and green paint denoting Port and Starboard... hehe... 

 

My intent on the RMS is to simply pull it from the housing. I don't really think there is a necessity to pull the assembly off of the block, but I understand a necessity to replace the rubber under it due to sheer age and rubber shrinkage/hardening. I think I'd have to pull the RMS assembly or the oil pan in order to do that properly. One or the other. Good enough reason, I suppose, to clean the oil off of the front axle. Just need to find the right sized 12pt socket to get those bolts off of the CV Shafts.... I don't even have 12 point sockets....

[Slartibartfast]

Yeah, I had to borrow a 12-point impact socket when I did the CVs in mine. I did give it a go with a chrome socket, but naturally it turned to glitter when I hit it with the 1/2" impact.

[gamellott]

2 hours ago, Slartibartfast said:

Yeah, I had to borrow a 12-point impact socket when I did the CVs in mine. I did give it a go with a chrome socket, but naturally it turned to glitter when I hit it with the 1/2" impact.

Armchair mechanicin here.... Do you recall any of the specifics about your impact setup? I'm scrolling through the Grainger website wondering what kind of proprietary tools I might need in order to fit an impact on the bolts without F-ing them up...

[Slartibartfast]

The one I borrowed had a U joint in it (I think it was this one, or very similar). The wobble was helpful. But I think I got an axle off the parts car with just a shallow socket and a separate impact-rated U joint.

[Slartibartfast]

Confirmed the size. 12mm 12 point.

[gamellott]

Thanks. Just ordered all of the crap needed to complete this. Also ordered a 14MMx1.5 tap to clean up the threads for the attaching hardware of the Upper Control arms. Guess I'm going to tackle Every Single Issue that I am aware of while I have the front end torn apart. It has been several years since I questioned what I was going to do on that... guess the time is now!!