Overdrive question.

[DavidApp]

I installed my rebuilt overdrive earlier this year and it has worked well after I got the solenoid sorted out.
The OD had a very slight leak soon after I installed it and at first I was convinced that it was either the drain plug or the solenoid mounting plate.

The leak has become more of a problem and I lose about a cup of oil a month. I can see the oil is coming from the join between the adapter plate and OD.
OD leak s.jpg
The sealant on the right is where I changed that gasket.

First question.
Does this type of leak tend to get worse with time?
I have bought a new adapter plate and gaskets from Rimmer Bro.
Looking at the gaskets I notice the gasket between the adapter and the gearbox some of the holes in the casting are covered.
OD adaptor gasket ofset s.jpg
OD adaptor gasket s.jpg
The OD side gasket has an unused hole along the bottom edge.
OD adaptor gasket od side s.jpg
What is the best sealant for this location?
David

[CJD]

I use Permatex 51813. It is an anaerobic sealer that will dissolve in oil...so if you use too much it should not clog the hydraulic passages in the OD.

[Sarastro]

That plate is notorious for leaks. I think it's just not strong enough to resist bending from all the forces on it.

Mine leaked at first, not too badly but worse than I was willing to tolerate. I took it all apart, put on a new gasket and was careful about making sure that the whole perimeter was sealed. It still leaks, but just an occasional drop or two. You may not be able to do better than that--or, if you do, please let us know what you did.

As for sealer, I'd take John's suggestion.

[DavidApp]

I could live with just a drip or two and that is what it appeared to be at first. Then it started to get worse. I checked the bolts were tight in the adapter plate when I noticed the oil on that ledge. Got a drip pan because it was getting so bad.

This is about 6 weeks worth of drips.
Oil leaked out s.jpg
David

[CJD]

You should drive it more, so most of the drips fall on the road instead of your garage floor...

[sp53]

Yes those one size fits all gaskets are confusing. What did the old gasket look like? I would not use that gasket. I would cut a new one with a leather punch set for the holes and high quality gasket material. I might used some of that red stuff that John mentions, the stuff is interesting. I used it on my steering box. However, in this case( and I do not know if this ok or not because I have little experience with ODs) but i would use some old school nasty hardening permatex and bond it.

[Rod-H]

Maybe you could fab up a little pump that will pump the oil from the little container back into the OD.

R

[Sarastro]

The suggestion of a better gasket is a good one. My TR4A's OD came with a much thicker, softer gasket than you get with today's gasket kits; it was about 1/16" thick. No sign of leakage. If I ever do this again, I'll make my own from gasket stock. The thin paper ones won't really seal anything.

[Graham H]

David you may have bent the adapter plate during instalment,I had tried everything I could think of to fit the OD back on the box until I finally found this video on YouTube A-type Overdrive Overhauling- part 8. I can't get the link to download here sorry but basically what he does is take out the operating valve plug and screw in a air hose addapter apply air pressure to operate the OD so you can lineup the last splines so they don't lock and brake or bend the adapter plate

Graham

[DavidApp]

Hello Graham

I did not rebuild the OD myself. It was done by a guy who has done a lot of them. He did state that he is going to use new adapter plates in future rebuilds. Sounds lie he may have had others leak.

I will see if I can find the video. I have seen the advice to be very carefull as you close up the OD to the gearbox.

David

[DavidApp]

Hello Graham

Thank you

Found and watched his video in fact I watched it a while ago. I like the idea of assembling the OD to the gearbox without the springs to check that everything fits. I would have thought that having got the splines aligned that way they should stay aligned. Could you turn the input shaft if the splines need a bit of help during assembly.

David

[Graham H]

Hello David,

When the OD is disengaged if you turn the output shaft during assembly all the parts that make up the splines turn together and will not align, if the OD is engaged one set of splines are locked which allowed the last one to rotate and align and it all comes together.
I found trying to align the splines before final assembly never worked, the slightest movement would put them out and lock the hole thing up as you get close to final fit, using air to engage the OD makes the job so much easier.

Graham

[DavidApp]

Hello Graham

So the dummy shaft is of little help if the splines can get misaligned so easily.

One of the comments in a thread attached to a vlog on the OD made sense. "Clean the area carefully and powder with flour so you can definitely identify where the leak is coming from"
There was another comment that made no sense at all. "Our shop does a lot of these OD jobs and we always attach the adapter plate to the OD first before mating the OD to the gearbox" Don't think you can do that at least on the TR3 OD.

I had thought it was the solenoid plate but noticing the oil along the adapter plate to OD I am assuming that is where it is leaking. I will do that test in the next few days. May even jack the back wheels up and run it up in gear. I have an inspection pit so I can get under the car with it running.

David

[Graham H]

Hello David,

The amount of oil that is leaking would seem excessive for the selector shaft O ring seals but that could be part of the problem. The other place I found hard to seal was the large OD drain plug which I finally fixed with some loctite on the thread, I also only used Aviation gasket cement on all the mating surfaces which has always been good.

Regards Graham

[DavidApp]

Got under the TR and cleaned the OD/transmission carefully and made sure the area was dry. Dusted it with flour to help show where the leak was originating.

Jacked the rear wheels up and ran the motor with it in second gear with the overdrive engaged. Got back in the pit to check it with it running. No extra leaks.

About an hour later this is the leak situation. I am almost certain it is the center of the adapter plate.

David
Leak s.jpg
leak from Pas side.jpg

[Madflyer]

I have a Alum valve cover and cork gaskets do not work so I cleaned cover an ran a bead of high temp seal silver let set over night and no gasket bead does not move adj valves a time or to never a leak to head. I would say do this to plate then with proper gasket the two might be enough. TR 's do not leak they mark there parking space. Madflyer

[DavidApp]

This is more than a leak it is a dribble.

As the adapter plate seems to be pron to bending I am supersized nobody has come up with a steel one.

David

[carpecursusII]

Was the gearbox assembled dry or used a sealant. This joint requires sealant. Warping this thick of an aluminum casting would take more load than exists in the system. I bet it was not assembled with enough/proper sealant.

[DavidApp]

The guy that did the rebuild said he used Yamabond 4 on the joint and no gaskets.

I have heard that that plate can very easily get bent during assembly. Along the bottom edge there is a long gap between bolts and the OD mating surface is narrow.

David

[Graham H]

HI David,
If the splines don't align in the last part of assembly or the oil pump drive cam catches on the piston roller there is extreme presser applied to the end plate, you will know it's not right when the output shaft locks up.
Have you checked the selector shafts for leakage?

Graham