Double the fun! 901/13 and 902/1 teardown and inspection

[daniel911T]

Pelicans!

This started as another thread, but I think the subject on that one was wrong, or at least no longer reflects reality. Here's the former thread: Transmission pain! or... Burned by "Caveat Emptor"

Very quick synopsis: My transmission in my '69T has been making funny noises, giving great trouble engaging first gear, grinding every time into second, and generally being balky and awkward about shifting.



My idea for an easy fix: buy a good used transmission, install, fill with swepco, drive until rebuild required... somewhere in the future. Sadly, this did not work out for me. The used transmission I bought turned out to be a 902/1, with flanges for Nadella or Lobro axels, which are naturally not interchangeable with my stub axles that fit.

Even worse, when I took a look at the drain plug I saw it was covered in an amount of fuzz I consider excessive... although many have said it was within the normal range. The remaining oil in the case (just a few tablespoons) was crunchy to the touch. Both for its incompatible axels, and for its metally oil, this box must come apart to judge the extent of the damage.

In the world of common fixes, I started cheap and worked my way to splitting the transmission case. I replaced all the shift linkage bushings, I cleaned and lubricated the shifter, I adjusted it very carefully, the clutch was right on adjustment, and was new, and I changed the oil for swepco 201. No improvement.

While working on the inspection, I have already found one nice obvious, easy problem that has already been fixed: I had failed to change the clutch fork bushing last time. There was a great deal of play in every direction on the clutch fork. With new bushing and new retaining plate, there is no slop at all. That should help somewhat.

Otherwise, the teardown of the 901/13 has gone pretty smoothly, I've learned a lot, and I've only had to buy one tool so far. (sadly, I destroyed the already roached 1st gear too) Not too shabby. I have copious pictures and several essential lessons learned that I'll share later tonight, when I'm not working on borrowed daylight.

Details to follow! Thanks a lot to those that helped me get this far on the earlier thread... I couldn't have gotten it this far without you.

Cheers!
-Dan

[daniel911T]

Here's the 901: I'm not going to say it's perfect or anything, but I think it looks much better than it was actiing....

In fact, the worst problem I saw, aside from those I created, was a very worn synchro on both 4th and 5th gear. This is odd because I had absolutely no trouble with either gear under any circumstances. First looks a bit rounded on the dog teeth, and the synchro looks a bit worn, but I don't see anything that would cause the shifting problems I was experiencing. Same goes for 2nd gear... it's not pristine or anything, but I was under the impression that the synchro was going to be missing or broken in half or something.

without further adieu:

Below, first and reverse:



... and the damage I did to first while removing it without the gears locked...




Overall picture of the gearset:



I don't like the look of the 4th and 5th synchro rings, but they didn't give me any trouble at all.



first gear:



first gear synchro and dog teeth. The ring looks bad, but the dog teeth look worn, but acceptable. (to my uneducated eyes)



Now we got the pinion shaft (also called main shaft) out and tapped the gears off.


Continued...

[daniel911T]

Here's second gear



And the second gear synchro and dog teeth:






To my untrained eye the synchro looks roached, but the dog teeth, while no means perfect, look serviceable.



The slider looks mercifully ok. These things are damn expensive!



Here is third:







...and fourth:



Finally fifth:



The fixed gears look just fine to me. There's no apparent damage and wear is even.

[daniel911T]

I did find one piece of obvious trouble: It was in this state upon removal, this is not any of my handiwork.


I was unable to take apart the input shaft because nothing I did could loosen that damn nut! I even broke out the torch... nothing helped. Eventually, the vice grips that I had holding the splines broke and stripped the jaws. (spline undamaged) I don't know how you're supposed to get this nut off short of explosives or plasma torches. (yes I did release the bent retaining tabs!)

And finally... I was amazed that all the bearings looked, and felt, like new. No missing or pitted rollers or balls anywhere, all surfaces smooth and happy. No evidence of high temperature. Simply perfect.

The only thing I did identifty in terms of bearing trouble, was that one of the cages for the intermediate plate input shaft bearing, was broken cleanly into 3 pieces exactly the same size. It was so precise that I was wondering if this was just the way the cage was constructed? Much closer examination shows that the breaks are not all on exactly the same angle. I hope the other transmission has a good one I can steal.

Please give me your thoughts on what you've seen so far!

Thanks All!

-Dan

[Jon B]

Dan,

Your transmission's been opened and repaired before, the damaged locktab is evidence of that. The large 1st gear appears to be dated 5/72 (?)- see if the reverse idler is etched 7497, and if it's dated. The 2nd gear synchro hub "dogs" look very marginal.

Look for signs of spalling or pitting on the ball bearing races, and pinion gear teeth.

[daniel911T]

Originally Posted by Werkstatt

Dan,

Your transmission's been opened and repaired before, the damaged locktab is evidence of that. The large 1st gear appears to be dated 5/72 (?)- see if the reverse idler is etched 7497, and if it's dated. The 2nd gear synchro hub "dogs" look very marginal.

Look for signs of spalling or pitting on the ball bearing races, and pinion gear teeth.

I agree that it's been open before. The bearings are quite different from the 902 bearings, not in dimension, but certainly in appearance. From all the bearings I've been able to get my eyes on, there is no pitting, scoring, discoloration, or any other evidence of wear on the bearings or races, with the one noted exception of a broken race. I think they must have been changed last time.

I was being kind about the second gear dogs. You should have heard the thing shift! I feared some of them would be missing or something!

As for the idler, it's dated 4/71 and the number 7497 matches. I think that's a shame. The idler in the 902 looked pretty bad, but if it's mated to first, then I guess I'll have to use it.

How hard is it to get a bearing race out of the intermediate plate? I may need to swap the input shaft bearing.

Thanks for the help! Next post will have the 902 teardown. It looks a lot better inside.

-Dan

[daniel911T]

Learned a lot the first teardown.
This one went just a tiny bit faster...

Here she is revealed:



This time I got straight to the taking it apart part.



I found some concerning things on the idler gear. This is a pretty big bummer, but not a project ender.



Getting straight into the gear stack... here's first:


I'm way happier about how this one looks than the 901. It's the same ratio. The dogs don't look very good, but the synchro is in great shape. The interface between this and the slider takes a good amount of effort and makes a satisfying snap going into place. The 901 first gear is quite loose, and takes very little effort to engage. I'm pretty sure that the one in the 902 is much closer to what they are supposed to look and feel like.


Going back to second:



and back to third:


In this case, I'm not even going to bother with 4th and 5th. They are flawless, just like the other one.

Impressions/conclusions
This 902 was FILTHY! However, as I dug through the muck and got a rough cleaning done, it became apparent that this is indeed much more healthy than my 901. The only thing I see that I really don't like is the dogs on 1st gear, and how beat up the reverse side of the idler is. Otherwise this box seems to look really good.

Plan
Because the gearsets have to stay matched, and one of my major problems was 2nd gear, I've decided that I'm just going to take the whole 902 input shaft with all the gear stack intact and drop it into the 901. The 902 gears will be added to the pinion shaft from the 901, and it will all go back in the 901 case.

My only complaint is that I would really like to move over my Z 5th gear, but I can't get it off the input shaft to save my life. That damn nut is on there in a way I don't know how to (non-destructively) cope with.

Is there a better way to mix and match? Do you see anything that needs to be replaced at this point?

Thanks!

-Dan

[Jon B]

Originally Posted by daniel911T

I was unable to take apart the input shaft because nothing I did could loosen that damn nut! I even broke out the torch... nothing helped. Eventually, the vice grips that I had holding the splines broke and stripped the jaws. (spline undamaged) I don't know how you're supposed to get this nut off short of explosives or plasma torches.

Tools in photos below are for locking & disassembling the input shaft. You can make a splined tool from an old clutch disc hub, or maybe someone will loan you one. I suspect the 4th & 5th synchros aren't as bad as you think, and might want to leave the shaft as-is. If you disassemble it, you'll have to torque it properly on assembly, keep that in mind.

If you heat the intermediate plate, the bearings will drop out. The mag plates wear more than the aluminum versions, so the bearings might actually be loose already.

[daniel911T]

All bearings are nice and tight in both.

Crazy idea... the aluminum plate fits the mag case... if it's a stronger part, is a swap possible?

Thanks
-Dan

[Jon B]

Originally Posted by daniel911T

I've decided that I'm just going to take the whole 902 input shaft with all the gear stack intact and drop it into the 901. The 902 gears will be added to the pinion shaft from the 901, and it will all go back in the 901 case.

If you do this, you'll need to swap bearing shells in the case as well, not easy to do. Any different parts you stack on the pinion shaft might alter the pinion depth. You're better off repairing the original 2nd gear with a new synchro hub. If you don't have the removal tool or a press, put the gear in a box and send it to someone who does. You can use a good hub from the 902 box for your original 2nd gear.

You cannot swap intermediate plates from mag to aluminum. You can purchase an aftermarket billet IP for a mag case, but the pinion depth would have to be re-set.

[tops911]

I used an old clutch disc and "C" clamped the to a work bench. I then inserted the main shaft into the disc and it all held to remove the big nut. I honestly found working on the transmission rather easy; easier than an old GM transmission I built as a kid.
good luck, Frank

[j911brick]

I think if you replace the pinion shaft you will need to set up the ring and pinion again. If I understand correctly you only had a problem with second gear. If thats the case I would probably just replace the ring and call it a day. The teeth don't look that bad, its your choice.

[daniel911T]

Mini update:

A man's got to know his limitations...

I'm taking the whole pile into RPM in Lorton, VA. They have the tools to switch around the dog teeth and grab all the best synchro rings. They also have the tools to loosen that evil nut and retorque it on the other end.

The 902 3rd, 4th, and 5th dogs and synchros look like they were installed yesterday, as do both of the sliders. I see those beautiful parts, and it would just kill me to put the 901 back together without taking advantage of what I've already paid for. I'm sure the experts can take care of that easily.

While they're in there, I'm going to ask them to do an inspection on the diff. It's going to be driving a very long distance, I want to be confident in the gearbox.

More to follow when I hear the mechanic's opinion.

-Dan

[daniel911T]

Stan, the mechanic from RPM took the time to actually go all the way through both gearboxes with me. Wow!

This is the plan:

Building on the 901/13 case.

Diff checked out good and won't be further messed with.

We are keeping 2,3,4,5 unchanged in the 901 case.

The input and pinion shaft from the 901 will be reused.

I plan to complete the build, including stuff like shift forks, etc... with the original parts.



Donor parts: The 902 is giving the following so that my car may live,

4th and 5th gear synchros and dog teeth. These will be installed on 1st and 2nd. These parts look like new.

First gear. I broke the one from the 901, so the 902 one goes in. It's dogs look bad, but they're being replaced with the perfect ones from 4th gear.

The 4/5 Slider and guide sleeves from the 902 will go to be the 2/3 the 901. These parts look like they left the factory yesterday and have never been used.



At this point, Stan has the 902 input shaft, and he owns the crazy looking huge socket required to get the damn nut loose. He also has my whole 901 pinion gearset. He'll be swapping some stuff around to give me a sweet set of gears for the "new" transmission. I'll be doing the building.

My mission now is to move the 902 input shaft intermediate plate bearing over to the 901, get everything all cleaned up and ready to go, then get building.

More as things progress....


-Dan

[BAO B]

Very informative Daniel911T,

I have a quick question on removing the gear stack.

I was able to removed the tail end cover and kept all pieces together.

My next step is to removed the intermediate plate, i did everything correctly except that I pushed in the 2/3rd gear to set it instead of 4/5 gear, which is need to be set in order to removed the intermediate plate.

My question is how do reset the gear back to neutral? Then, re set the 4/5th gear.

Thanks in advance
Bao B

[daniel911T]

Originally Posted by BAO B

Very informative Daniel911T,

I have a quick question on removing the gear stack.

I was able to removed the tail end cover and kept all pieces together.

My next step is to removed the intermediate plate, i did everything correctly except that I pushed in the 2/3rd gear to set it instead of 4/5 gear, which is need to be set in order to removed the intermediate plate.

My question is how do reset the gear back to neutral? Then, re set the 4/5th gear.

Thanks in advance
Bao B

WELCOME TO THE FORUM!

I'm not totally sure I understand your question, but I'll take a stab at it.

The way I understand how it works, only one of the sliders can be engaged at any given time, so if you're trying to engage 5th you should:

1. ensure the 1/R slider is in neutral

2. ensure the 2/3 slider is in neutral

3. get the 4/5 slider into neutral

4, double check that 1/r and 2/3 are fully in neutral, then push the 4/5 slider back (towards the differential) to engage 5th.

The system is designed to lock the other two sliders in neutral when any one is engaged. To move 5th, you have to be in neutral on the other two.

Alternatively, you could take out the bolt on the bottom of the intermediate plate and disassemble the detent mechanism (or at least try)

Good Luck!

-Dan

[BAO B]

Hello dan again,

i'm ready to put the gears back in the main case. My question is how do i set the 4/5 gears back to neutral once after the gears are in the main trans. Case?
Of course, prior to putting the gears into the main case i selected the 4/5 gear.
Also, would you use sealant for the gaskets on both sides of the int. Plate?

Thanks, bao