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MG MGB Technical - Benefit of an LT77-gearbox in the MGB :-)

I just found some pictures from the clutch change I had to do last june. At this day I discovered a nice additional benefit of my conversion to the LT77-gearbox, which I did in 1984: You can take the gearbox out and leave the engine in place!
This works, because the LT77 is much shorter and the propshaft-flange does not go over the cross member.

I was alone in the workshop and it took just 3 hours to remove the gearbox, change the clutch and refit it.

Sorry for the bad quality, I took this pic with my phone.


And this is the reason for the unexpected clutch change. This clutch had covered only 1000 miles before it was destroyed. I suspect, that the release bearing did not clear the clutch surface and so burnt everything...


What motor do you have in your MGB?

"the release bearing did not clear the clutch surface"

Not sure what you mean by this. The release bearing is always in contact with the cover plate when the pedal is released because there is a spring in the slave trying to push the piston out, which takes up all the play in the linkages that end. If the friction plate wasn't being fully released when the clutch pedal was right down you would have had difficulty selecting gears at a standstill, with grinding in reverse unless that gear has synchromesh.
PaulH Solihull

And so why haven't you tried a high quality roller release bearing with a retraction spring on the slave? Cheers, Vem
vem myers

Shouldn't need a retraction spring, the MGB V8, midget 1500 and any number of clutches use a roller bearing with no pull-off spring. Any roller bearing that needs one is not up to the job.
PaulH Solihull

@ Darno: its a 1.930cc bored stage2-engine, with an aluminium-oilsump.

@ Paul: I know that the release bearing in the MGB usually is troublefree - I never had this problem in more than 30 years. But this time, after I changed the clutch, I had the disaster you see in the 2nd pic after about 1.000 miles. The (NEW) release bearing was worn beyond the metal and even some metal was shaven of, the cover plate (the part, were the release-bearing comes in contact with) was burnt out from heat, had fallen into 2 pieces and was just held in place (kind of) by he first motion shaft.
And I was able to change gear without scratching at least for the first few 100 miles
I exchanged the destroyed clutch cover for a good used one I had lying around, fitted a new release bearing and from then on all was fine.
Dont ask me, what went wrong, it still is a misery to me.

What brand of release bearing did you use?

It might be worth checking the dimensions of the bearing. A few years ago, I bought a Midget release bearing from M*ss and the dimensions were completely wrong.

I didn't even bother trying to fit it and fitted a good, used item that I had.
Dave O'Neill2

The message about the advantages of the LT77 is welcome. Especially if you have a V8 with all the fuel injection gear. The clutch problem is bad luck - these probs occur occasionally - and defy explanation. ... and all this in English. Congratulations !
Roger W


I have a LT77 in my V8 what bell housing are you using?
It is a short gearbox but very heavy.

Bob Fisher

@ Dave,
I fitted a complete clutch set from Borg Warner and the release bearing had the right size, it remains a misery

@ Bob,
The bell housing is a bit tricky :-) ASAIK you cannot and you never could buy a bell housing to mate an early MGB-engine for the three-sync g/box to an LT77. What I did back in 1982: I took the gearbox-casing from my broken 3sync-box, cut it at "the right place", had an aluminium-plate welded to the bell housing-part and fitted the LT77 to this. The clutch release was repositioned to the side of the bell housing with original parts. Maybe it gets a bit clearer with the attached pic.
From back to front you see:
the modified crossmember with LT77-rubbermounts
the /box itself
the new adapterplate for the g/box
the rest of the original 3-sync-casing with relocated clutch machanism


Forgive my lack of knowledge but what is the make of the LT77 g'box.
And what model does it come out of. I have done a similar conversion with a Toyota T50 [5 speed] with a close ratio conversion. They are getting a bit scarce now and only just able to handle the power.It looks a nice setup.
R F Murray

The LT77 is a Rover gearbox and was used extensively during the 80s in Rover SD1, Land Rovers and Sherpa vans. It is not a particularly good gear change, particularly between first and second, which needs to be taken slowly to prevent graunching.

It can handle quite a lot of power, certainly over 200 bhp. It was steadily improved over the years and each update is identified by the suffix letter on the gearbox. The best ones are F, G and H. You have to be careful about where the box came from as Sherpa boxes have ratios that aren't very suitable for an MG, and of course Land Rover boxes are designed for 4-wheel drive. The boxes often require rebuilding at about 100,000 miles.

An updated box was introduced in the 90s called the R380. The first few MG RV8s had an LT77, but most have the R380. I have an R380 in my MGB V8 conversion. The remote on the box is a bit longer and the lever has a dogleg in it so it can come through the hole in the MGBs tunnel.

Mike Howlett

This thread was discussed between 05/04/2013 and 26/04/2013

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