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UNUSUAL OVERDRIVE PROBLEM


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On a run this weekend with the TR Register I had an unusual issue with the od.

We drove up to a mates farm, about 150 miles of high speed and traffic driving. No problems and parked the car under cover for the weekend.

This morning we went to a pub on various country roads, some a bit rough.

About 10 minutes into the drive I thought I felt a momentary od dropout. Could have been a bump. Kept going with the od working fine even on bumps.

A few minutes later I noticed the amps gauge reading a few amps -ve. I went to disengage the od and and it wouldn't drop out. Down a hill, into neutral, turned the engine off for a few seconds and restarted. The amps gauge recovered to normal but the od was still engaged. It stayed engaged for the next 45 minutes over some very rough roads. It was engaged in all gears including 1st and didn't drop out when changing gears.

I assumed the solenoid had seized, maybe burnt out, in the up position.

Get to the pub and I feel under the car and pull the lever down. The solenoid didn't click down but the actuating arm did move.

I assumed the od was still engaged so decided that I'd have lunch and then drive back the 130 miles without using reverse.

After lunch drove off and the od had disengaged. Once I was over the Blue Mountains and on a freeway I reengaged the od and it worked fine all the way home.

The solenoid is maybe 20 years old.

?????

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Which of your TRs, John?

If TR2, which type of switch is used for the overdrive?  Pull/push or the circular blob with its little lever?

You say that when you reached the pub, you pulled the lever down. Perhaps the rubber gaiter on the bottom of the solenoid is jamming the actuator lever, or, as Bob suggests, something else has jammed it in the "operated" position.

Ian Cornish

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I think I would be checking for wires shorting to earth keeping the solenoid pulled in, although Bob could well be right.  Yesterday I thought a rear wheel bearing had seized, I turned off the main road into a side road over some potholes (plenty of those around) and started to get a screeching noise from passenger side rear wheel. I stopped and reversed a few metres and after an initial screech all went quiet, did another 15 miles after with no noise. I am now assuming a small pebble had dropped between the brake drum and backplate and become lodged, reversing dislodged it.

Ralph

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13 minutes ago, Lebro said:

Rough road - maybe some dust got in the solenoid area & jammed it ?

Bob.

Could be. I'm going to pull the tunnel off and have a look around.

In all likelihood there won't be anything visible and I hate it when I can't find a cause.

A new solenoid is cheap so I will probably replace it anyway.

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16 minutes ago, ianc said:

Which of your TRs, John?

If TR2, which type of switch is used for the overdrive?  Pull/push or the circular blob with its little lever?

You say that when you reached the pub, you pulled the lever down. Perhaps the rubber gaiter on the bottom of the solenoid is jamming the actuator lever, or, as Bob suggests, something else has jammed it in the "operated" position.

Ian Cornish

Daily driver TR2 with its original A type od but with a isolator switch to operate on 3rd. It has the original type push pull switch which I'll pull out and clean up.

The symptoms are such that it is not a switch problem. Even if the switch shorted out the od should have disengaged when the car wasn't in 3rd or 4th.

Edited by John McCormack
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Looking very much as if it is the solenoid's plunger getting jammed in the "operated" (up) position.  As Bob suggests, could be dust between plunger and the casting's tube.

If you need to, removing the tunnel on the TR2 is so much easier than on my TR4.

Ian Cornish

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57 minutes ago, ianc said:

Looking very much as if it is the solenoid's plunger getting jammed in the "operated" (up) position.  As Bob suggests, could be dust between plunger and the casting's tube.

If you need to, removing the tunnel on the TR2 is so much easier than on my TR4.

Ian Cornish

If the TR4 is like the TR6 I know what you mean.

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When you have the tunnel out, do a “works” mod and fit a quick release cover plate. Plus extra holes by the hand brake to allow actuating over removal and cleaning.

https://www.tr-register.co.uk/forums/index.php?/topic/75190-gearbox-tunnel-replacement/&tab=comments#comment-706817

Makes life a bit easier for future maintenance 

Iain

 

Edited by iain
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On 3/28/2021 at 8:50 AM, Ralph Whitaker said:

I think I would be checking for wires shorting to earth keeping the solenoid pulled in, although Bob could well be right.  Yesterday I thought a rear wheel bearing had seized, I turned off the main road into a side road over some potholes (plenty of those around) and started to get a screeching noise from passenger side rear wheel. I stopped and reversed a few metres and after an initial screech all went quiet, did another 15 miles after with no noise. I am now assuming a small pebble had dropped between the brake drum and backplate and become lodged, reversing dislodged it.

Ralph

Or its one of the brake shoe hold down clips dropped off.

Stuart.

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21 hours ago, stuart said:

Or its one of the brake shoe hold down clips dropped off.

Stuart.

Good point, I will check for that. The handbrake needs adjusting anyway now the shoes are bedded in a bit.

Rallph

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14 hours ago, roy53 said:

on a newly rebuilt o/d gearbox i have a leak from the bar that holds the solenoid adjuster.[ 57 moss book ]  ideas please .

Item 55 is an o' ring that is probably the cause of the leak. You will need to take off the solenoid and the bracket/cover plate (53) two bolts and two nuts on studs, release them evenly as there is a strong spring pushing behind the plate. The o' ring is pushed on to the operating shaft and forms an oil seal when the cover plate is  tightened up. Renew the gasket 52 and fit/ re-adjust the solenoid. Good luck.

Rob

14 hours ago, roy53 said:

 .

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7 hours ago, RobTR3 said:

Item 55 is an o' ring that is probably the cause of the leak. You will need to take off the solenoid and the bracket/cover plate (53) two bolts and two nuts on studs, release them evenly as there is a strong spring pushing behind the plate. The o' ring is pushed on to the operating shaft and forms an oil seal when the cover plate is  tightened up. Renew the gasket 52 and fit/ re-adjust the solenoid. Good luck.

Rob

Rob, I'm hoping you are mistaken on this as I've just done this job and I did not remove plate 53. I think it's just a case of removing the actuating lever (57)and then the collar (56) and you can change the o ring (55) and put it all back together. There is an o ring on the other side which requires a pin to be tapped (quite a bit of "tapping" in my case). 

Both o rings were missing on mine, probably gone hard, cracked and fallen off. I hope I've got this right and the seals should be on the outside and not the inside but please correct me if I'm wrong. Easier to fix whilst it's still on the bench. 

Neil

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17 hours ago, NCS_TR3A said:

Rob, I'm hoping you are mistaken on this as I've just done this job and I did not remove plate 53. I think it's just a case of removing the actuating lever (57)and then the collar (56) and you can change the o ring (55) and put it all back together. There is an o ring on the other side which requires a pin to be tapped (quite a bit of "tapping" in my case). 

Both o rings were missing on mine, probably gone hard, cracked and fallen off. I hope I've got this right and the seals should be on the outside and not the inside but please correct me if I'm wrong. Easier to fix whilst it's still on the bench. 

Neil

Neil/Roy 

I did this job a couple of years ago and I definitely removed the cover plate, as far as I can remember to get at the o' ring. I don't remember it being on the outside of the cover plate. The diagram in the Moss book, does show it on the outside which is a bit confusing admittedly. The only other reason to remove the plate would be to renew the gasket, but it was a leaking o' ring I had to replace. Perhaps other members can clarify.

The o' ring on the R/H side is a tap out of the rolled pin on the adjustment lever, which is then removed, and the o' ring pushed on. I did this one as well.

Rob

 

 

 

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Have you found the cause and sorted the problem John? Sounds very much like an intermittent short to earth to me. Favourite place on the 4A for this is one of the leads to the switch shorting to the steering column as a result of damaged insulation. Maybe wiring on the TR2 is different but if the switch shorts to earth on the 4A it results in o/d being engaged in all gears, including REVERSE!

Best regards,

Tim

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On 3/31/2021 at 9:45 PM, tim hunt said:

Have you found the cause and sorted the problem John? Sounds very much like an intermittent short to earth to me. Favourite place on the 4A for this is one of the leads to the switch shorting to the steering column as a result of damaged insulation. Maybe wiring on the TR2 is different but if the switch shorts to earth on the 4A it results in o/d being engaged in all gears, including REVERSE!

Best regards,

Tim

Hi Tim,

I've been sailing for a few days so will play with it over the next few days.

Unfortunately, it can't be a short in the solenoid wiring. Any short will cause the od to disengage. This problem was the od staying engaged when disconnected at the dashboard switch. The od needs power to stay engaged and there are no power sources downstream of the dash switch.

I think Bob (Lebro above) and a few others theory of the solenoid being kept up by debris in the solenoid (which is open from the bottom) is most feasible.

I have washed it out with WD40 so will see what happens over the next few weeks. If the od doesn't disengage I won't use reverse.

So far it has been working fine since the run last weekend.

Next you are downunder I'll take you for another run in the long door TR2. It is driving superbly. All the gremlins are fixed.

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If the short was between the relay and the switch it would operate the relay and keep the o/d permanently engaged. Not likely admittedly, but don`t rule it out.

Ralph

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On 3/31/2021 at 11:25 AM, RobTR3 said:

Neil/Roy 

I did this job a couple of years ago and I definitely removed the cover plate, as far as I can remember to get at the o' ring. I don't remember it being on the outside of the cover plate. The diagram in the Moss book, does show it on the outside which is a bit confusing admittedly. The only other reason to remove the plate would be to renew the gasket, but it was a leaking o' ring I had to replace. Perhaps other members can clarify.

The o' ring on the R/H side is a tap out of the rolled pin on the adjustment lever, which is then removed, and the o' ring pushed on. I did this one as well.

Rob

 

 

 

Rob, thanks and your memory is correct. I took the plate off today to check and have attached the photo that confirms the seal is on the inside. I thankful you posted this before I was ready to refit, a far easier job on the bench. I did follow the process of removing the bolts a bit at a time due to the spring that sits behind it. I do also note that the o ring I have from Moss is not quite the same shape as the one I took out. The old one is more of a square section and thre moss one is more a normal (circular) one. Need to get a new gasket before refiting but thanks for positing the correct method. 

Neil

IMG_20210402_162606.jpg

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Neil 

Glad you got it sorted. I don,'t recall where I got my o' rings from but it was probably Moss and I've had no leaks since, so you should be OK. I found the biggest issue was re-adjusting the solenoid correctly as the W/M method doesn't result in enough adjustment. I find I have to move the adjusting lever incrementally off centre to the hole in the overdrive casing until I get the overdrive to engage - trial and error! What fun we have.

Rob

 

 

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10 hours ago, John McCormack said:

I think Bob (Lebro above) and a few others theory of the solenoid being kept up by debris in the solenoid (which is open from the bottom) is most feasible.

Hi John, I guess it depends on the type of overdrive. My A type solenoid has a rubber seal at the bottom to stop the dirt getting in. I don't know if the J type does or doesn't. I had overdrive on my Jag Mk2 as well and that had a seal as well. Worth checking if you are meant to have one on as it may stop a repeat. 

Neil

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15 hours ago, Ralph Whitaker said:

If the short was between the relay and the switch it would operate the relay and keep the o/d permanently engaged. Not likely admittedly, but don`t rule it out.

Ralph

I'll keep that as an option thanks Ralph. The circuit should still be broken by the isolator switch when the box is out of 3rd or 4th. By my thinking there would need to be a power source between the isolator and the solenoid to keep the solenoid engaged electrically and there is no such source on that short wire to the solenoid.

I haven't take the tunnel off yet, just been working from underneath. If I need to I will check the wiring throughout as you suggest.

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5 hours ago, NCS_TR3A said:

Hi John, I guess it depends on the type of overdrive. My A type solenoid has a rubber seal at the bottom to stop the dirt getting in. I don't know if the J type does or doesn't. I had overdrive on my Jag Mk2 as well and that had a seal as well. Worth checking if you are meant to have one on as it may stop a repeat. 

Neil

Thanks Neil. My solenoid is open at the bottom, any rubber seal that might have been there is long gone. I suspect the solenoid has been there for 20 or more years.

Further thinking on the issue also raises the possibility the od is sticking internally preventing the actuating arm dropping under its own weight when disengaged. Again, not likely as it would drop on bumpy roads, but a possibility.

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6 hours ago, John McCormack said:

Thanks Neil. My solenoid is open at the bottom, any rubber seal that might have been there is long gone. I suspect the solenoid has been there for 20 or more years.

Further thinking on the issue also raises the possibility the od is sticking internally preventing the actuating arm dropping under its own weight when disengaged. Again, not likely as it would drop on bumpy roads, but a possibility.

John, you said you cleaned it out with WD40, was it quite rusty. Mines been in for years but it's clean inside, shiny. The seal looks like the one in the photo attached to the plunger. That is for the A type overdrive. 

Neil

Screenshot_20210403_080356.jpg

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