Who’s rebuild an LT77 Suffix H?

mick 1986 · Oct 21, 2020

I have my LT77 in a few pieces on the workshop floor. The bearing on the layshaft (input end) gave up, so I thought I would do a full rebuild instead of just replacing the bearing. I didn’t really take many photos of how it came apart as I have access to the workshop manual, but I’m struggling.

I’m trying to fit first gear, along with its bearing and bearing carrier, and then the taper roller bearing onto the main shaft. The manual says to fit these parts, then secure with a circlip. I can’t get the circlip into the groove as the bearings and carriers seem to stack up too much. I think the baulk rings and “cones” are all inline. I have disassembled the bits 5-6 times, but it’s always the same. I didn’t take any photos as I was too fed up (trend setting here). I have attached a screen shot of the workshop manual step.

Any help is greatly appreciated.

jamesmartin · Oct 21, 2020

mick 1986 said:
I have my LT77 in a few pieces on the workshop floor. The bearing on the layshaft (input end) gave up, so I thought I would do a full rebuild instead of just replacing the bearing. I didn’t really take many photos of how it came apart as I have access to the workshop manual, but I’m struggling.

I’m trying to fit first gear, along with its bearing and bearing carrier, and then the taper roller bearing onto the main shaft. The manual says to fit these parts, then secure with a circlip. I can’t get the circlip into the groove as the bearings and carriers seem to stack up too much. I think the baulk rings and “cones” are all inline. I have disassembled the bits 5-6 times, but it’s always the same. I didn’t take any photos as I was too fed up (trend setting here). I have attached a screen shot of the workshop manual step.

Any help is greatly appreciated.

first job is fit 1st 2nd syncho hub,thin circlip either side then on 1st side fit the baulk ring assembly all correctly aligned, thrust washer gear bearing and sleeve, turn shaft with rear upwards and ensure gear spins free and baulk ring assembly is free, you can then fit rear bearing rtc2914

mick 1986 · Oct 21, 2020

jamesmartin said:
first job is fit 1st 2nd syncho hub,thin circlip either side then on 1st side fit the baulk ring assembly all correctly aligned, thrust washer gear bearing and sleeve, turn shaft with rear upwards and ensure gear spins free and baulk ring assembly is free, you can then fit rear bearing rtc2914

Thanks for the reply @jamesmartin

I think that is what I have done. The problem is when I press the bearing on, it doesn’t go far enough to get the circlip on. There are 2 grooves for the circlip, but it doesn’t reach the one I think it should. It’s almost as if I can’t press the bearing on far enough, but I can’t work out what it’s actually getting bound up on. The gears all spin freely, as does the baulk rings and “cones”.

jamesmartin · Oct 21, 2020

any endfloat in first it goes when bearing fully fitted

mick 1986 · Oct 21, 2020

jamesmartin said:
any endfloat in first it goes when bearing fully fitted

I have just came back to the farm and had at it on my “press”. I now have this (photo). The only issue I can see now is the first gear bush doesn’t turn. I personally don’t think that’s a problem. The bush has a groove machined round its ID, this is connected to the shaft through hole, so the bearings can still receive oil. Why does the bush need to turn when the bearings rotate round the bush, and the gear rotates round the bearings?

jamesmartin · Oct 21, 2020

mick 1986 said:
I have just came back to the farm and had at it on my “press”. I now have this (photo). The only issue I can see now is the first gear bush doesn’t turn. I personally don’t think that’s a problem. The bush has a groove machined round its ID, this is connected to the shaft through hole, so the bearings can still receive oil. Why does the bush need to turn when the bearings rotate round the bush, and the gear rotates round the bearings?

sleeve wont turn when correctly fitted, its pressed tight by the bearing,gear should and baulk ring assemble be free to move,they can easily become misaligned and jam as bearings pressed home

mick 1986 · Oct 21, 2020

jamesmartin said:
sleeve wont turn when correctly fitted, its pressed tight by the bearing,gear should and baulk ring assemble be free to move,they can easily become misaligned and jam as bearings pressed home

Thanks @jamesmartin thats how it is at the minute.

I have left it for tonight, the main shaft, input shaft, and layshaft, are all assembled now. They are all sat in the middle part of the gearbox housing. I will rebuild reverse in the morning, fit the front case, and test for lift on the shafts. Hopefully the old shims will work, but I can make new ones if not.

Thanks again for the help.

jamesmartin · Oct 21, 2020

mick 1986 said:
Thanks @jamesmartin thats how it is at the minute.

I have left it for tonight, the main shaft, input shaft, and layshaft, are all assembled now. They are all sat in the middle part of the gearbox housing. I will rebuild reverse in the morning, fit the front case, and test for lift on the shafts. Hopefully the old shims will work, but I can make new ones if not.

Thanks again for the help.

its very much worth loctiting the outer bearing races into the case front ones after your think shimming is correct
i bolt sandwhich plate and main case together then fit shims bolt on front cover check for no end float and both shafts arent stiff to turn

mick 1986 · Oct 21, 2020

jamesmartin said:
its very much worth loctiting the outer bearing races into the case front ones after your think shimming is correct
i bolt sandwhich plate and main case together then fit shims bolt on front cover check for no end float and both shafts arent stiff to turn

Thanks for the heads up. Do you use bearing retainer, or just thread lock? Yeah I was going to use some short bolts to hold the case to the plate, then bolt the small cover on and check for lift.

What do you aim for on the lift? I’m hoping to get 0.000”, but is 0.001” acceptable?

jamesmartin · Oct 21, 2020

mick 1986 said:
Thanks for the heads up. Do you use bearing retainer, or just thread lock? Yeah I was going to use some short bolts to hold the case to the plate, then bolt the small cover on and check for lift.

What do you aim for on the lift? I’m hoping to get 0.000”, but is 0.001” acceptable?

either whatever you have they should be a snug fit it just tops them spinning in the case, rear layshaft race often wears the case making shimming difficult, you dont want any lift ie no free play and 2 thou preload but if shafts turn freely and arent stiff thats ideal

mick 1986 · Oct 21, 2020

jamesmartin said:
either whatever you have they should be a snug fit it just tops them spinning in the case, rear layshaft race often wears the case making shimming difficult, you dont want any lift ie no free play and 2 thou preload but if shafts turn freely and arent stiff thats ideal

Sounds easy enough. Thanks again. I will let you know how I get on. Hopefully it will be rebuilt tomorrow.

jamesmartin · Oct 21, 2020

mick 1986 said:
Sounds easy enough. Thanks again. I will let you know how I get on. Hopefully it will be rebuilt tomorrow.

once you got shimming right and front cover bolted up ,leave the bolts holding the sandwich plate and case together in place, you can then lay box down to fit the 5h gear etc, then stand it on its nose so you can remove the bolts to fit gasket and extension housing

mick 1986 · Oct 22, 2020

jamesmartin said:
once you got shimming right and front cover bolted up ,leave the bolts holding the sandwich plate and case together in place, you can then lay box down to fit the 5h gear etc, then stand it on its nose so you can remove the bolts to fit gasket and extension housing

Thanks, I will do.

Will the gearbox need to be “run in”? If so, how many miles should that be done over? I was thinking, go stead for the first full tank, so 430-450 miles.

mick 1986 · Oct 22, 2020

Well, with the original shims, the layshaft is solid, so I need to try and get that surface ground a few thou. The main shaft has 0.15mm of lift (0.00591”) so I’m guessing that 0.006” will be ok for that? I can’t see 0.00009” making a great deal of difference.

mick 1986 · Oct 23, 2020

The gearbox is back together, and I can select all 6 gears. That’s a HUGE relief.

I noticed a small amount of engine oil on the floor. After having a look around, it’s coming from between the flywheel housing and the engine, so I have ordered new gaskets and output seal. I went with a “genuine” seal as I’m hoping to do this once. Hopefully it will all be back together tomorrow.

tottot · Oct 23, 2020

A good new gasket has beads of sealer already on it. [ 200 I take it ] The last crank seal I fitted to mine [ "genuine "] was hard to get in. Half an hour in the freezer sorted it . Crank land must be clean and dry before fitting new seal.

mick 1986 · Oct 23, 2020

tottot said:
A good new gasket has beads of sealer already on it. [ 200 I take it ] The last crank seal I fitted to mine [ "genuine "] was hard to get in. Half an hour in the freezer sorted it . Crank land must be clean and dry before fitting new seal.

The one I have just got has a small “bead” around the centre and a few other places, but I was advised to “put a small bead” around it to make sure it seals. I don’t want to be doing it again. He said the crank seal is a pig, but it has the plastic fitting cup, so can’t be that hard....can it?

jamesmartin · Oct 23, 2020

mick 1986 said:
The one I have just got has a small “bead” around the centre and a few other places, but I was advised to “put a small bead” around it to make sure it seals. I don’t want to be doing it again. He said the crank seal is a pig, but it has the plastic fitting cup, so can’t be that hard....can it?

its the main bearing joins that need sealant as well as round were the seal housing fits around the crank

mick 1986 · Oct 23, 2020

jamesmartin said:
it

its the main bearing joins that need sealant as well as round were the seal housing fits around the crank

Do you think I’m opening a can of worms if I take the flywheel housing off? It drips oil, and has done since I bought it, but it’s nothing that has bothered me. It’s only because the box is out, and I really want to get it completely leak free that I have the bits.

jamesmartin · Oct 23, 2020

mick 1986 said:
Do you think I’m opening a can of worms if I take the flywheel housing off? It drips oil, and has done since I bought it, but it’s nothing that has bothered me. It’s only because the box is out, and I really want to get it completely leak free that I have the bits.

i doubt youll get it completely leak free, if it drips its worth fitting a seal

Who’s rebuild an LT77 Suffix H?

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