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MG TD TF 1500 - 3 speed gear jumps out

Since a few weeks I heard a rattle from the gear/remote - like a rattle snake. I replaced the plunger in the remote - but it doesn't solve the problem.

After a ride of 350 miles last weekend the 3rd gear jumps out when the gear was without load, but not everytime.

I'm not sure but it may be, that the 4 gear jumped out one time too.

At the moment I have following questions:

1. Is it possible to ignore the fault the next 1200 miles? It is easy to select the 3rd gear again or select an other speed gear.

2. What may be the first diagnosis?

3. Is there anyone in D who has a reliable gear box after transition to 5 speed? (I don't want to do change to 5 speed).

4. Does anyone know a workshop in D who knows how to rebuild a gear box?

It's annoying because the gear box was outside while changing the clutch 800 miles before :-(.
W_Mueller

Winfried,
Give me a call when you get the chance.

Regards
Declan
Declan Burns

I would suggest dropping the drive shaft and making sure the nut is tight on the end of the main shaft. Do NOT try to drive it holding it in gear. You will wear out the shifter forks quickly doing so.
Kurt Byrnes

"I would suggest dropping the drive shaft and making sure the nut is tight on the end of the main shaft. Do NOT try to drive it holding it in gear. You will wear out the shifter forks quickly doing so."

+1
MAndrus

Hi Winfried,

My brother's TC race car started to jump out of 3rd gear and be OK in 4th .... and then it would jump out of 4th gear and be OK in 3rd. I found that a screw which locates the selector to the shaft had sheared. When the selector was jammed one way for a while, it would not fully engage 4th gear but went too far (didn't matter) into 3rd gear. ........ Then after a race or two, it would slip and jam the other way. It would not engage fully in 3rd gear but went too far into 4th. I rebuilt the gearbox but could have just taken the top off (with gearbox still in car) and replaced the sheared selector locating screw.

I hope you have the same problem as my brother because that problem should be fixable with the gearbox still in the car.

Bob Schapel
R L Schapel

I think Bob is right on. And easy to fix as he says.
Peter Dahlquist

Thanks at all

Tomorrow I will drive the vehicle to a pit. First, I'll check the tight fit of the screw on the gear output shaft. I have ordered springs, balls and a gasket (as a template for a nitril gasket) and will open the cover of the gear box in the car if the loose screw is not the reason. I hope I will discover the cause with your helpful hints.

Good fellow Declan has emailed some documents too. So I'm prepared.
W_Mueller

The nut has been tight and was secured by a split pin. That wasn't the culprit.
W_Mueller


In the meantime I have the ocassion to get a gear box from a TF.

Does it fit to early TD? The clutch housing is different because the shaft of the early TD is thinner and the according lever differs. Does the 7 1/4" clutch housing make problems with a TF gear box? Or can I use the TF clutch housing together with the 7 1/4 clutch?
W_Mueller

Winfried,
I received the photos of the TF gearbox you have sourced and it looks pretty good and unmolested. Before you go changing gearboxes check the free play on the shafts as mentioned in the re-build instructions that I sent you. I am convinced that your main problem is selector related and nothing to do with actual gears. Replacing the three springs and balls could very well solve your problem without taking the gearbox apart. This is mentioned in the instructions.
If you know the history of the TF gearbox from the seller and the price is at all reasonable, I would be inclined to grab it.
I would use your existing clutch and bell housing and replace the release and spigot bearings and the first motion shaft oil seal.


Regards
Declan
Declan Burns

Declan

I'll follow your hints at saturday.

W_Mueller

Until now no visible reason for the issue.

One ball (2nd rod) stucks in the hole of the gearbox and didn't come out with help of a magnet. I must wait for a stronger magnet and for new springs and balls. But I guess the culprit is the fork. in that case it will be hard to purchase because most dealers are unable to deliver.
W_Mueller

Winfried,
That stuck ball could very well be the root of your problem.

Regards
Declan
Declan Burns

The contact points of forks can be welded up and ground back down to size to provide the proper clearances, so they don't necessarily need to be replaced.

Tom Lange
MGT Repair
t lange

Winfried,

I had the same problem of a ball stuck in the casing, I removed it using super glue.
You need a metal rod about 5mm diameter and 10 cm long, a plastic tube with the outside diameter the same as the hole of the gearbox and super glue (the gel type).

cut the tubing to about the depth of the hole, push it all the way down into the hole, put a VERY small amount of glue on the end of the rod then push it through the tube onto the ball, hold it there for a few seconds the pull it out.
I my case the rod, tube and ball all came out easily.

The tube is to prevent any excess glue from spreading.


John
J Scragg

Thank you John - I'll try if the super magnet fails.
W_Mueller

No progress

The new springs are longer than the old ones but the gear still jumps.

I wasn't able to pull the ball of the 1rst and 2nd shifter shaft - not with a stronger magnet, not with vacuum and not with super glue. But I guess that is independent.

I'd bought a used gearbox which now is on its way to a specialyst workshop.

If it is the shifter fork - is it possible that 3rd jumps and 4th still holds?

W_Mueller

My experience with a quick fix to the relatively common problem of 3rd gear disengaging on overrun or no load is to replace or add an additional spacer between the center bearing and the mainshaft circlip (MOSS part #324-480). This will diminish the space between 3rd gear and its sliding hub and allow fuller engagement of 3rd gear with its striking dog. On acceleration the helical nature of the gears tends to push these parts together whereas on deceleration they are forced apart and hence become dis-engaged.
There is probably considerable wear on the 3rd gear fork and as pointed out this can be repaired by welding, using a "hard facing" rod, and then grinding to fit. The measured width of a NOS fork is 0.290 +- 0.003" as measured from several forks. If you decide to replace the fork, I think I still have a few NOS ones.
Hugh Pite
H.D. Pite

Another comment I might make is that it is impossible to determine the condition of the all important 1st gear cog on the cluster without totally dismantling the gearbox. This, along with wear on the lay shaft, is the greatest weakness of the TD/TF gearbox.
Hugh Pite
H.D. Pite

I hesitate to throw in again, but, I keep thinking about this. I had my TF gear box open and on the bench. Ready to change the cluster gear. All the square headed screws were in place and lock wired. When disassembling I found the 3rd/4th shaft screw was severed just above the shaft. There was a looseness there. The point is all looked good on inspection but there was an underlying problem. And I think about the balls; one would have to be missing and not locking that shaft in position.
Peter Dahlquist

Hugh,
I spoke to Winfried the other day and mentioned that same washer you are referring to and asked him to measure the play as I had a similar issue with my gearbox and that part was actually missing. Mine did not jump out of gear but was grinding when shifting down.
He measured the play and it was very little and sent me a photo. It looked ok. I believe it is a selector fork problem combined with the fact that he cannot get the balls out. Hard facing and re-grinding to spec is a good suggestion or purchasing one from you. It is great to know that you have a stock of such parts.

Regards
Declan
Declan Burns

This thread was discussed between 10/07/2017 and 23/07/2017

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