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peter t

A Type Overdrive oil leak

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The Solenoid mount side plate of my overdrive still leaks, even after ensuring the plate was flat, fitting a new gasket and smothering both sides with Hylomar

 

Thicker gasket, silicon sealing compound .....?

 

Anyone faced this and solved the problem with a 'cunning plan' all ideas gratefully received

Edited by peter t

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The threads might be pulling out of the aluminum housing or the plate cracked. Another possibility could be a leak around the bolts, Crush washers and sealant in that area might help. Also, verify that the leak is actually from the cover plate and not running from another area and check that an O ring is fitted around the operating valve shaft on the inside of the cover.

Berry

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I had exactly this problem. I was running the transmission on a test-rig so it was easy to have several goes at fixing this.

 

There is not enough width in the sealing faces around the bolt holes. Oil gets into the bolt holes and out past the washers.

 

I did the things you have done. Gaskets, compounds, lapping but still had oil weeping.

 

I fixed it by modifying the plate to accept O-rings around the bolts. I have the machinery to do this accurately.

It would be difficult by handwork.

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Hi Peter,

 

Check that the leak is not from the gear selector shaft O rings. If they are leaking it will run down and appear as if the plate is leaking...ask me how I know... :)

 

Cheers

 

Tony

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I had this problem after fitting a recon o/d. However many times I took off the plate & replaced the gasket I still had a leak. I even had the plate milled, but that didn't solve the problem. In an attempt to get the beggar to seal I also over-tightened one of the bolts and had to heli-coil it. D'oh!

 

Careful inspection of the accumulator revealed witness marks indicating the piston was sticking so that pressure wasn't being relieved (insufficient travel to open the bypass holes).The result was that the (unrelieved) hydraulic pressure was being applied to the plate, distorting it and causing the leak. From memory (risky) the pressure build-up behind the stuck piston caused the piston and sleeve to push against the cover plate. The firm that supplied the o/d sent me a replacement accumulator assembly. Problem solved.

 

I guess it's unlikely you have the same problem, but perhaps worth checking if the sleeve has shifted at all, or if either piston or sleeve show uneven wear. The giveaway was that the plate didn't leak immediately after being refitted, but did after the car had been driven (even once everything had cooled down). Only a remove/reseal/replace fixed it for another cycle of frustration.

 

Hope this helps. Good luck.

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First try to find exactly where the leak is. Sounds obvious but there are many little places on these units that can leak and of course it runs down and drips from the plate.

 

On a test rig its easy to wash the unit down and put flour on and run it to see where the oil first appears.

https://www.flickr.com/gp/90670218@N04/T7QCVh

 

I have often thought that I probably would not have found all the leaks, if I had not run the unit on a test rig.

 

There is quite a bit of expansion when these are warm. Re-torque the bolts when hot but do be careful or you will be Helicoiling.

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This is all good info guys

i'm fairly sure its the gasket/bolt combination,

o rings would be great but outside my scope

 

i'll check all the other ideas and let you know how i get on (but don't hold your breath)

 

Thanks to you all

 

:rolleyes:

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No, you need to know exactly what the leakage path is. Or you are just guessing how to stop it.

Clean it with solvent and dry it. Dust with a bit of flour. Watch and see where it comes first.

 

If it gets into the bolt holes then a nut and washer wont stop it.

 

You might try PTFE tape, a new very flat smooth washer and some sealant.

Old washers are always dished and scuffed up.

 

This will probably work but not for long. But then you will know what's happening.

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Can anyone confirm that the "O" rings on either end of the operating valve cross shaft and the gasket under the solenoid plate can be replaced  with the overdrive in situ.

I have minor leaks from the case at each  end of the cross shaft and I'm assessing how big a job repairing them will be. My main concern is the operating valve dropping if the cross shaft is moved too far.

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If you can drive the pin out of the setting lever with the trans. in place, it should be doable. I remember drill&tapping the setting lever for small allen screw (don't remember the size) that had the shank turned to the same size as the pin. This makes replacement much easier next time.

Dropping the operating valve rod is usually a problem as it can be fished out with a bent wire or magnetic tool.

Berry

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Thanks Berry. I'll add this to my list of jobs for this Australian winter. The  "O" rings will be replaced with Viton as I suspect the  "O" rings that failed were NBR.

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Hi Mike,

  when I did this two years ago on my TR4 I was informed that the 'O' rings are not circular in cross section - they have a square cross section.

If you fit the wrong type/size etc they will grip the shaft and you will have problems in the shaft not rotating back to rest.

I got a repair kit form ORS in the UK - have yet to fit them.

The pin holding the  rigging arm is tapered. TRy and tap it out in the right direction.

I made an odd tool that sat on the arm and one could screw the pin out. It just about worked

 

Roger 

P1060227aa.jpg

P1060229aa.jpg

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Thanks Roger. I'll try ORS for the O rings- if I get them from this supplier I know they'll work. The tool is a good idea for working in the confined space next to the OD case- I'll see what I can make using the same principles.

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Had a similar problem on my 4A. Couldn't get the side plate to seal whatever I did. Solved the problem by getting a new side plate. A very slight warp on the original plate was enough to prevent it sealing. Used Wellseal on the gasket and it was fine. It was easy to see the oil oozing out around the edge of the side plate before I fixed it. The O ring on mine wasn't the problem.

I did all the work under the car with the overdrive in situ. I used ring spanners and filed one down so it was thin enough to fit over the bolt head behind the operating lever. Don't over tighten or you will be in the proverbial.

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Thanks Keith. Its reassuring to know that the work can be done in situ. I'll check the side plate on an engineer's block while I have it off to replace the gasket and O ring.

The O ring behind the setting lever will also need replacing - I plan to move the cross shaft inwards enough to access this and remove it with a pick.

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