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MG TD TF 1500 - Broken gear box case at mount

I have a problem about which I must educate myself in the next twelve hours.

I am a new owner of a '55 TF, so I don't know the correct terminology yet. My shop manual hasn't arrived and I haven't found a good diagram on line. I don't have the car here to look at so that I can give a better description.

There is a small extension at the back of the gear box case through which a bolt connects the tranny to the frame or to the mount. The extension is broken off.

> Can the car be driven while I find a fix?
> Can the extension be brazed to the case satisfactorily?
> What is that part of the transmission called? Is it the "Tailshaft" casting? Availability?
> What should be done to the tranny and the casting when the part is replaced?
> (I know the answer to this ...) Can it be replaced without removing the engine/tranny?

The problem appeared after the front engine mount was replaced and while the transmission mount was being installed. Both were done with the engine in the car. I did not do the work.

I had planned to drive the car and learn about it before considering pulling the engine. There was no indication that it was necessary.

Thanks for any advice that you can give to me.

- Lonnie
LM Cook

Hi Lonnie, the piece is called the rear gearbox case. It's not uncommon to have the ring-like piece of the case broken. Is that the problem with yours. I've been thru that. I had the piece welded back in, but it didn't hold. A fix (the fix) is to drill through the angled flanges and install a bolt. I'll attach a couple of images showing what I suspect is your problem, and a fix that has worked for me.
It's probably not to smart to continue driving the car with the rear mount broken. Yes, you will have to remove the gearbox to do the repair. The image here shows the broken piece after being welded back in. Bud

Bud Krueger

What worked - bolt through flanges - Bud


Bud Krueger

Mine broke too. I too welded it, but it let go, the day before I was leaving town with the car. I was able to cut a hole for the bolt with a torch, leaving the transmission in the car. I used an electric drill with a 1/4" bit to clean up the hole cut with the torch. It worked for me, but I would not recommend it. I was so proud of my fix, then I saw on this forum that it is a common repair.
-David.
D. Sander

Having trouble posting a reply and follow up question.

- Lonnie
LM Cook

Seems like there is a limit to the size of post on the forum. I'll break my dissertation into two posts ...

>> Bud -

Thanks for your fast response, photos, and description. Also thanks for resurrecting your old thread.

After I posted my question, I found Dave Braun's repair on his site that you discussed in your thread.

Questions to follow.

- Lonnie
LM Cook

My question ...

See Moss "TD-TF Gearbox" diagram. (I tried to link to the page in the catalog, but the forum software blocked it.)

ORIGINAL ARRANGEMENT:
Did the original #124 "FORK, rear mount" (325-140) go through the fork and the "ring-like" piece?

And did the #125 "CLEVIS PIN, fork" (325-140) go through th fork and the "ring-like" piece in your first photo?

If so, the engine/tranny would be able to rotate a little along the axis of the crankshaft.

REPAIR
Does the fix that you and others describe use the same fork and clevis pin?

The arrangement of the clevis pin prevents the engine/tranny from rotating along the axis of the crankshaft. Instead, the engine/tranny can move a little fore and aft.

Both of the movements are minor. I am just trying to make sure that I understand the setup.

>> Dave -

You don't know how much I don't want to remove the engine and transmission!

Thanks so much to both of you for your help. I am breathing a little easier.

- Lonnie
LM Cook

Maybe these pictures will help.



Frank Cronin

photo of the transmission support bracket with really worn rubber mounts.

Frank Cronin

Lonnie, I believe the main purpose of the bolt at the rear is to stop the gearbox from lifting. It may help with fore and aft movement as well. There is a stay at the front of the engine to prevent rotation.
Max Irvine

LONNIE,
There is a size limit on photos for uploading,,,
I use http://www.imageresizer.com/ to resize them to make them smaller,,,
Click on DOWNLOAD, and get the one that is ONLINE


SPW
STEVE WINCZE

I agree the clevis just hold the tranny down. The cast "wings" seated in the rubber blocks in the mount box should take most of the fore/aft force (ie from the clutch pedal).
George Butz

The repair does continue to use the original fork. It is the clevis pin that gets replaced by the bolt, or pin, through the angled flanges. Yes, the allowed axis of rotation is now orthogonal to the original system. But, as others have pointed out, the system intent is to control vertical movement without transmitting the forces to the car's framework. Perhaps Dave Sander's technique might work for you. Good luck. Bud
Bud Krueger

IMHO, to have the rear mount crack as shown, must be a result of a lot more than just resisting upward motion!I would think that repeated foward and backward motion/forces would result in the crack in the casting.
SPW
STEVE WINCZE

Sure have to agree with you, Steve. But it's not an uncommon occurrence. The force that's most prevalent seems to be the longitudinal twisting of the engine and gearbox upon acceleration. Worn motor mounts, front and rear, could well translate that into fore and aft movement of the engine/gearbox assembly. At any rate, it's one of those things that happens. Bud
Bud Krueger

The amount of metal cast to hold the clevis pin is just not sufficient to hold that much force. The modification, with a 1/4" grade 8 bolt provides far more strength.
-David
D. Sander

I made the same modifications as shown with the drilled thru bolt. I'm a retired Mechanical Engineer. So what has been bugging me about this fix is it puts the axes of rotation just opposite of the original axes. I'm guessing that the rubber bushing take care of torquing of the engine and tranny? My plan is to get my 53 TD on the road for the first time in the spring. So I have no experience with what happens here. Thanks
RER Rosa

I've been pondering the axis-of-rotation question, too. I feel that the original eye in the transmission case was positioned to allow the engine to rotate a little with torque.

In the fix as shown with a bolt through the wings on the tranny case, could this be an option for the fork?

Instead of using the original fork, use an eye bolt with the eye larger than the diameter of the bolt. The sloppy fit would allow the engine to rotate a little with torque.

Pic of forged eye bolt:
http://i21.geccdn.net/site/images/n-picgroup/PTY_J94024.jpg

All of the force between the bolt and the eye bolt would be concentrated in a single point. Don't know if that would cause a failure.

Also, don't know if a grade 5 or grade 8 eyebolt exists.

I wonder how many of the flanges on the trans case were broken when the engine was jacked up to install a new front engine mount without loosening the rear tranny mount(??)

I've owned my TF for two weeks and have driven it for only a couple of hours, and I'm already trying to sound like an expert! So take my comments with a grain of salt.

- Lonnie
LM Cook

Lonnie, have you made contact with the Orlando Classic MG club yet? There is a fellow in the club that has been working on, racing, and restoring T-series cars for over 50 years. He has a vast supply of parts as well. George
George Butz

Lonnie,
mcmaster-carr is about the best place to find all sorts of stuff!!

http://www.mcmaster.com/#general-purpose-eyebolts/=py3iyp

SPW
STEVE WINCZE

Thanks for the McM-C link. The site showed a larger selection of eyebolts than I found on the Fastenal site.

I'm gonna drive the car while I learn more and evaluate ways to fix the problem.

With no experience, I'm only guessing ...

An eyebolt with washers and rubber sleeves on each side would secure the rear of the engine side-to-side and would allow a little rotation with engine torque. Depends on the dimentions of the eyebolt vs space available and on what I learn when I actually start the process. The front mount should secure the engine front-to-back.
McMaster-Carr (1):
http://www.mcmaster.com/#general-purpose-eyebolts/=py4nxo
McMaster-Carr (2):
http://www.mcmaster.com/#general-purpose-eyebolts/=py4n2a

You have shown that the original fork oriented 90-deg has proven successful. So, I have at least two options.

Diagrams in the Workshop Manual and photos in this thread helped me visualize the original setup.

> George: Yes, I have met some members of the Orlando Classic MG Club. Looking forward to enjoying my TF with them and asking questions.

- Lonnie

LM Cook

A portion of another diagram in the Workshop Manual ...

LM Cook

Lonnie, looking at the drawing, it looks like you might want to get the Moss parts 281-408 $19.95 RUBBER MOUNT SET, rear (3 pieces). The Moss catelog blow-up are very informative and most of us use Moss part numbers as universal identifiers even if we acquire the part somewhere else (donor car, other vendor, etc.) If you haven't browsed the Moss site, you probably should:
http://www.mossmotors.com/

Jud
J K Chapin

I would advise against buying rubber parts from Moss. Most rubber parts I have purchased from them has dissolved and turned to rotted junk in a matter of months. Abingdon Spares rubber, on the other hand, has held up quite well for me. Rubber from Abingdon has. "ASL" cast in to it.
-David
D. Sander

Don't disagree (or always agree) but the point was that the Moss parts pictures are very helpful.

Jud
J K Chapin

Thanks for the information about Abingdon Spares. I'm still gathering sources for parts. Too late - front and rear mounts from Moss were installed last week.

The diagrams and descriptions from the Moss catalog were my only reference until I received the MG TD/TF Workshop Manual. It has opened a whole new world of knowledge.

I'll use the diagram numbers in the Moss catalog when referring to parts.

Thanks again for all of the help and advice that you guys are giving me.

- Lonnie
LM Cook

This thread was discussed between 22/12/2013 and 24/12/2013

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