What to fix with gearbox out

sebackman · Feb 1, 2022

I'm having my auto gearbox taken out for an overhaul and a new converter. I've got a new converter, a shift kit and a full rebuild kit for the TH400 so that will be fine. I'm having an expert do the work.

I'm also going to exchange the bearing on the drive shaft for a SKF bearing.

What else should/can be done with the gearbox out.

Are the oil seals at the back of the engine possible to exchange from the rear side with engine in situ? If so are there more that one? Part no? Pictures?

What else?

Kind regards
//Rob

360modena2003 · Feb 1, 2022

Read the thread on the "Upgrade".

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sebackman · Feb 7, 2022

Hi 360Modena2003,

I have read the thread and done a search here but I cannot find so much info. The gearbox will be totally overhauled but what else.

Is it possible to change the main seal between the engine and the gearbox from the outside with the gearbox out?

Are there any other gaskets, seals , bearings or other things that should be replaced at the same time?

Kind regards
//Rob

360modena2003 · Feb 7, 2022

sebackman said: ↑

Hi 360Modena2003,

I have read the thread and done a search here but I cannot find so much info. The gearbox will be totally overhauled but what else.

Is it possible to change the main seal between the engine and the gearbox from the outside with the gearbox out?

Are there any other gaskets, seals , bearings or other things that should be replaced at the same time?

Kind regards
//Rob
Click to expand...

I recommend you get the Transgo SK400 shift kit, 10 inch torque converter with 2500 stall and master rebuild kit from Raybestos.

If you want to go all the way like I am doing, get a low gear set as well.

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raemin · Feb 7, 2022

On my car the gearbox harness (kick-down and reverse) was quite damaged by the heat. These are the cables that go from the left side of the trans to the hole of the transmission tunnel that reaches the top left side of the shifter. Maybe you could also drill an additional hole (and make a proper tap) on the right side of the tunnel, so as to be in a position to adjust the vacuum valve from the passenger side. This will give you a bit more flexibility in order to adjust the shift points.

sebackman · Feb 9, 2022

Thank you for the input.

It seem like I'm in good order with a 10"/2400rpm converter, a full Raybestos overhaul kit and a Transgo kit on the shelf. I also found someone to do it. I have bought the bearing for the drive shaft.

I will check the cables.

Are there any seals that needs replacing or gaskets needed to the toque tube? I have ordered the seals I can see in the manual but a confirmation would be helpful.

Also I can read that it is important to mark up parts/mounts as we pull it apart. What exactly need to go back inte exact same place, ie what to mark up and potentially how.

Thanks

raemin · Feb 9, 2022

I cannot comment on these parts. I would suggest to keep the stock regulator (it's already very aggressive) and discard the one that could be provided in an upgrade package. On my car all Teflon bits were replaced with stainless equivalents: more leaky but can sustain more heat (to be discussed with your transmission shop). I've also bought a deeper oil pan (4WD?), nothing fancy, just 1/2'' deeper.

I am quite disappointed by the (cork?) pan gasket so if you come up with a satisfactory one just let us know!

As far as the installation is concerned, this is typically the sort of job that is a peace of cake... as long as you have a transmission jack! The tricky adjustment is to mate the transmission input shaft into the converter. The transmission weights so much that it's hard to notice whether the shaft is properly inserted or stuck against the converter internals. This being said that's the only tricky step and unlike the engine bay there is not much that can be forgotten in the process.

sebackman · Feb 15, 2022

Hi Raemin,

Understood but in many posts people have written that it is important to marks how certain drive shaft parts are connected PRIOR to taking it apart. I just want to find out what that means. Is that to retain originally balanced parts?

Does the drive shaft have to go back to the same exact spline position in the couplings due to balance?

Does the drive shaft have to be positioned in the same exact length position in the couplings? I guess it can move slightly between the couplings?

Do the couplers have to come off when taking the drive shaft out?

What is the bolt torque when reinstalling the couplings and the torque tube bolts? There is no info on this in the work shop manual.

If so how tight are the length tolerances when re-installing , 1mm?

Does the torque tube have to be re-mounted in the exact same position?

There is no room for a deeper oil pan on my car as the sub frame covers the gearbox sump. She is a convertible.

Thanks
//Rob

raemin · Feb 16, 2022

I don't remember taking such precautions back then: all parts are individually balanced, the bearing in the torque tube is auto-centered, etc. The coupling position is quite hard to miss, as unless it is in the appropriate location, it will not line-up with the torque tube opening that allows to torque the fastener.

We replaced the tranny twice, I just don't see the blob of paint we usually use when we want to put everything back in the exact same position. This might not be the proper way though...

360modena2003 · Mar 22, 2022

Could you explain in detail how you removed the transmission, in particular how the 6 bell housing bolts were accessed.

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