View Full Version : Gearbox Rear Seal

10-11-2004, 12:34 PM
Anyone had experience changing out the gearbox rear seal on a TR6? (I'm refering to the seal on the mainshaft sticking out of the tailend of the gearbox.) No overdrive on mine. Just wondering if it's a DIY job or a job for the LBC mechanic.


10-11-2004, 12:45 PM
Hi Cain.
Im unsure on the TR6 but on the Sports 6 it's very straight forward, Remove the drive shaft and output flange, pry off the seal, Put on new one, Its always good to know what all the tourqe spec's are.
I know over simplified but shouldnt be too difficult.
Good luck

10-11-2004, 01:09 PM
I did this just a few days ago.

1. Remove rear section of exhaust
2. Remove drive shaft
3. Remove that large 1-1/4 nut from the shaft. I used a big screwdriver to keep the shaft from turning while I turned the nut.
4. Pull the cap off and pry the old seal out.
5. Install new seal
6. Reassemble in reverse of disassemble. The large cap nut is torqued to something like 90 lbs.

I recommend liberal use of penetrating oil on the exhaust components and the large cap nut a day or so before you want to do this. The entire process took about 2 hours and I started the process pretty clueless.

Email me if you have any questions.


10-11-2004, 01:41 PM
Thanks for the info, guys. I'm glad to hear that I can do this without having to pull the tranny and take it apart.


10-11-2004, 10:39 PM
I agree with everything stated above, however, (and you'll only not do this one once) while you have everything disassembled, run your fingernail along the surface that the new seal is going to ride on, if you can feel any wear, take some emery cloth to it and polish it up. I mean you'll only not do this on once beacause if there is wear, or a build up of crud there and the new seal does not seal as a result (meaning you now have the "oportunity" to do it all over again), you'll never forget this. Also, make sure and lube anything that will come in contact with the new seal well for reassembly as not to tear, or distort the new seal.

Rick O.
10-12-2004, 10:12 AM
2. Remove drive shaft

[/ QUOTE ]
It's advisable to match mark the drive shaft and gearbox flanges before disassembly to maintain the balanced orientation between the two upon reassembly.

12-02-2004, 01:59 PM
I'm finally getting around to doing this job. I need confirmation on the shaft nut size. Is it truely 1-1/4 inches? I got everything apart the other night and noticed I don't have anything lying around big enough to take that puppy off. So, I'm probably going to have to go buy or borrow something unless you guys have any other ideas.


12-02-2004, 02:50 PM

My 72 was 1-1/4... I had to go out and buy a socket to fit it... I think that was the biggest 1/2" socket that I could find.


12-02-2004, 08:49 PM

I'm getting in on this a little late, but I just went through a pinion seal replacement on the differential of my TR4 - a little similar to what you're doing. I don't know how much trouble the old gearbox seal will be to remove, but the seal on my differential was a bear... until I used the slide hammer trick. See here for details:


Good luck!

12-03-2004, 11:08 AM

Thanks for the info. Unfortunately I haven't gotten past the 1-1/4" nut yet.


I ended up getting a socket to fit the nut yesterday. But, I can't hold the shaft still. I tried sticking a screwdriver in one of the bolt holes on the shaft and ended up breaking the screwdriver. I think I'm just going to have to wait until I can get someone to help me hold the shaft while I loosen the nut. I was thinking either a pipe wrench on the shaft or possibly put it in gear and have someone hold the fan shaft on the front of the engine.

12-03-2004, 11:45 AM
Wow, yours must've been much tighter than mine.... I used the biggest screw driver that I could fit in the flange bolt holes. I let the screwdriver head mash up against the transmission an the tunnel and was able to turn it.

They make a special tool to hold the shaft from turning. I figure if I had access to some metel fabricating tools I could make something... You might be able to fashion something out of a 2x4 board... maybe cut a hole into it to fit the socket through and literally bolt the board to the end of the shaft. Or (easier) cut a semicircle out of the side of a 2x4 and bolt two bolts of the flange to the board... see attached pic for a description of my idea.

Just thinking in the wind here.... I usually end up hurting myself when I try my crazy ideas though.


12-03-2004, 12:03 PM

Actually, that sounds like a good idea. If my neighbor can't help me tonight, then I may have to do that.

Yeah, I understood the concept of using the screwdriver to hold it in place, but it bent then popped out of the handle. I figured I would just wait until I could get some help before I killed myself.

12-03-2004, 04:37 PM

Just did the one on the wife's car prior to reinstalling the trans (frame-off restoration of sorts). This one was a 'bit' snug also. Ended up drilling two holes in a piece of scrap angle iron to match adjoining bolt holes on the flange, bolted it up, strapped the trans down to the bench and attacked the nut with a 3/4 drive breaker bar and a two foot cheater. Whole thing was pretty anti-climatic after all that set-up, turned the nut about 1/4 turn and it came off by hand after that. Would have been more difficult with the trans still in the car and working from underneath.

And, as Steve99 mentioned, clean the tailshaft throughly and check for any rough spots or you will be enjoying this experience again.

12-04-2004, 10:41 AM
OK. Got the job done last night. But, before I close her up, I noticed the new seal seems to go in deeper than the placement of the old seal - i.e., closer to the bearing on the shaft. I put the flange back on and everything seems to be sealed, but I won't truely know until I take it for a spin.

Maybe the old seal was just out of place.

12-04-2004, 10:53 AM
Where is the seal in relationship to the edge of the gearbox? Is it flush, recessed, or protruding? I would think it should be flush.

12-04-2004, 05:03 PM
It is recessed - I'd say by half an inch or maybe a little less. The old seal was about a quarter inch recessed if I remember correctly.