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Layshaft upgrade


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Just started pulling apart my gearbox and found the layshaft totally cream crackered - haven't got all the gears out yet to check for damage, but they look OK from the top. Browsing previous threads, it would seem that an upgrade is due. I have seen mention of using Stag components and I see that Revington offer an upgrade. Does the casing need machining for any of these mods or is it just limited to replacement layshaft and gear cluster?

By the way, what's the sequence of dismantling the mainshaft. My manual goes on and on about Churchill tool such and such but doesn't actually say whether you start with the input shaft or 'tother end (or maybe I'm just being stupid). In the past I've left gearboxes to other people but I thought I'd have a crack this time. Any hints and tips welcomed (leave out the crosshaft tips - I cross-drilled and roll-pinned it last time I did the clutch and it is perfect still).

I'll need to clean out all the iron fillings from the box and overdrive and was thinking of running it with a flushing oil once it's all back together (just in the workshop jacked up). Any views on whether this would be beneficial or indeed harmful?

Jerry.

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Jerry,

 

I had good success a couple of times rebuilding 'boxes using the Robert Bentley Official Triumph Workshop Manual - but never did attempt to rebuild an O/D box; just removed and refit a rebuilt unit.

 

There is a modified cluster gear with doubled-up needle bearings as well as a deeper-hardened layshaft to go with it - Racetorations offer these and probably others do too. I suggest consulting with such suppliers for recommendations on other pertinent component upgrades.

 

Cheers,

Tom

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Jerry the overdrive on my TR5 has had the stag double beariing fitted together with a closer ratio 1st gear. Steve Barker who owned the car before me had the work done by J & E engineering. They are in Rossendale Lancs.

If you pm me I will let you have steves number and you can chat it through with him if it helps.

:D

Edited by Rex Wyer
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Just started pulling apart my gearbox and found the layshaft totally cream crackered - haven't got all the gears out yet to check for damage, but they look OK from the top. Browsing previous threads, it would seem that an upgrade is due. I have seen mention of using Stag components and I see that Revington offer an upgrade. Does the casing need machining for any of these mods or is it just limited to replacement layshaft and gear cluster?

By the way, what's the sequence of dismantling the mainshaft. My manual goes on and on about Churchill tool such and such but doesn't actually say whether you start with the input shaft or 'tother end (or maybe I'm just being stupid). In the past I've left gearboxes to other people but I thought I'd have a crack this time. Any hints and tips welcomed (leave out the crosshaft tips - I cross-drilled and roll-pinned it last time I did the clutch and it is perfect still).

I'll need to clean out all the iron fillings from the box and overdrive and was thinking of running it with a flushing oil once it's all back together (just in the workshop jacked up). Any views on whether this would be beneficial or indeed harmful?

Jerry.

You have to remove the laygear shaft, so that the gear cluster is lower in the casing. Only then the input shaft can be removed. The difficult part is removing the main shaft : you have to slide the rear ball bearing from this shaft and out of the casing : this is done easiest by putting the whole box under a press and put pressure upon the end of the shaft and lower the shaft as far as possible, taking care of the gears and rings. Then it is possibel to lever the ball bearing out of the casing , together with the shaft, with two large screwdrivers, and then slide the bearing further of the shaft and take the shaft out of the casing forwarth and upwarth.

Clean all the parts after dismantling, not when the box is put together again : the swarf will gather somewhere in the box and mix with the oil.

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Thanks for the input chaps. Suddenly remembered to check the Technicalities CD and there's a whole chapter dedicated to gearbox dismantling - should have checked first. Not much on upgrades though so any further info on what to consider welcomed.

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Jerry

Only just spotted this post; must remember to check the 5 forum more often!

After destroying 2 lay shafts & junking most of the box internals on the 2nd occasion, I had the Stag radial thrust race mod done on my 6 many years ago by a guy in Essex who raced 2.5 PI’s & have had no problems since.

 

This did involve machining the box internally but I don’t know if the Racetorations offering requires similar. I think you can also fit a Stag box to a 5/6 but the ratios are different; what I don’t know is if it’s possible to transfer the internals into the Stag box & use the Stag lay shaft to avoid machining.

Edited by Richard CRawley
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  • 1 month later...

Just thought I'd update this thread.

I am told that the Stag thrust bearing conversion is no longer that easy as some of the parts are no longer available. Installation does require machining of the gearbox casing.

The accepted modification (for road cars) is to bore out the laygear to take two sets of needle rollers at the rear and thus half the load/double the life.

I have been told that some of the new layshafts are insufficiently hardened and some of the synchro cups are of poor quality.

I have had my layshaft modified with the two sets of needle rollers and stuck with the standard thrust washers. As these had survived the onslaught from shredded needle rollers, they don't appear to be that much of a weak point. I had the new layshaft hardness tested and it was pronounced 'very good'.

I am replacing the second gear 'top hat' bearing which is known to be weak, with the later steel two piece component.

During the clean up of the overdrive I discovered that two thrust washers had broken up and the planet gear carrier was damaged. Quite how it still worked perfectly I find amazing. Tough old things these overdrives.

At this point I must enthuse about Overdrive Repair Services in Sheffield. I sent up the damaged carrier overnight delivery on Monday. They stripped, refaced, made up a special thrust washer and rebuilt the planet bearings Tuesday and got it in the nights post for delivery back on Wednesday. We don't see service like this ofton so top marks to the boys at ORS.

Hoping to get the thing back together for a run up Prescott on Sunday, otherwise I'll be using the Legacy Estate.

Just crossing my fingers that the B&B new clutch works properly. Previous experience has been a bit 'hit & miss' but I'm told that they are much better these days.

Chin Chin,

Jerry

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I am replacing the second gear 'top hat' bearing which is known to be weak, with the later steel two piece component.

Jerry

Don't know about the two piece steel second gear bearing (on the main shaft), but the one piece steel bearings can be too tight : I once fitted one and it got stuck on the main shaft after only a short journey : it was impossible to remove this bearing but by cutting it and the main shaft had turned blue. Since then I ream these steel replacement a little bit with a brush, made up of sandpaper flaps, on an electric drill.

These bearings should be a little loose on the shaft. When some force is needed to slide it on the shaft, it is too tight.

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Just thought I'd update this thread.

I am told that the Stag thrust bearing conversion is no longer that easy as some of the parts are no longer available.

 

At this point I must enthuse about Overdrive Repair Services in Sheffield. I sent up the damaged carrier overnight delivery on Monday. They stripped, refaced, made up a special thrust washer and rebuilt the planet bearings Tuesday and got it in the nights post for delivery back on Wednesday. We don't see service like this ofton so top marks to the boys at ORS.

 

Just crossing my fingers that the B&B new clutch works properly. Previous experience has been a bit 'hit & miss' but I'm told that they are much better these days.

Chin Chin,

Jerry

 

Hi Jerry

Nice to hear things are coming along OK with your box/OD rebuild but, oh dear, lets hope my modified box outlasts me then! Do you know what's no longer available?

 

Can verify the service provided by Overdrive Repair Services is 1st rate as I have used them before; a while ago now though!

 

Re the B&B clutch, I have posted on this a couple of times on the 6 forum (have a look back through the archive); if you’ve bought the right one it should be OK.

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  • 1 month later...

Another update due just in case anyone else follows this route.

Have driven 1000 miles since putting the box back together and everything OK apart from a small oil leak from the O/D area - not sure where yet. Changed oil and cleaned filters after 500 miles and nothing big fell out.

I can confirm that the B&B clutch works well. Slightly heavier than the previous Laycock.

As mentioned before the laygear now has two needle rollers at the rear, hardened shaft and standard thrusts. I had to replace the constant pinion gear on the layshaft as its thrust face was worn. Be careful if you do this as the angle of the teeth varies between boxes. I am told that there are at least 3 variations and if you get the wrong one (as I did at first) it won't mesh with the other gears.

The steel 2nd gear bearing that I had planned to fit did not make it into the box. After the comment by Marvmul I checked this very carefully and found that the oilway in the steel bearing did not line up with the oil feed from the gear, and neither did it have a drilling to lubricate the mainshaft. I ground the oilway on the bush so that it lined up but it was far too hard to drill. I decided that replacing a bronze bush with lots of oilways with a harder steel bush with fewer oilways was likely to lead to wear of the mainshaft or gear or both and that I'd rather replace a cheap bush. So the new steel bush is on the shelf and an original spec bronze bush went in to the box.

Many thanks to all for advice.

I didn't make Prescott in the end, but did a track day at Donnington with no problems and have the Nurburgring coming up in a couple of weeks.

Jerry

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Ron, I'm afraid I don't know.

I sent away the laygear and it came back all done with bearings fitted. I assume all the specialists use the same method - I happened to use Racetorations on this occasion.

Jerry

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