GT6 '70 GT6+ transmission rebuild

[19_again]

The tranny was rebuilt by DPO, but then parked after a year or two then sat for 20 years. My local shop has it and suggests that aside from the obvious seals etc. I replace the lay gear . The reasoning is very small rust spots on some teeth, I mean "get your glasses" small, that are the result of sitting with these teeth out of the fluid and condensation working on them. I'm told this will attack the hardness and manifest itself in a noisy tranny at best and broken teeth at worst. It is only evident in about 1/3 of the gear and only on some of those, as the other 2/3 was in fluid.
This is a very expensive gear and this shop doesn't cut corners, but I'd like to know that it's necessary before coughing up this kind of money, with seals bearings etc I'm around $700 plus labor.
and more importantly the part shown in VB is for 71-73, Nigel's site requires a call for this year, TRF's site is just too much work to find anything and BPNW (my preferred as they are a sponsor) doesn't get that deep into these type parts. Does anyone have experience at this level, can I even use the VB part?
Thanks,
Mike

 

[vagt6]

First, you may be able to source a good gearbox for less than you're getting ready to spend on your rebuild. Be patient and ask around, I bet you can find a good one for less than $700+.

Nigel's part probably refers to the single rail gearbox found in MKIII GT6s. It may not work in the earlier, two-rail boxes found in MK1s and MKIIs. Andrew, can you confirm this??

Best way to find out is to ask Nigel or someone knowledgeable at desks at BPW or Roadster Factory. I guarantee Nigel Cosh at SpitBits knows, for sure, and will be glad to help.

The lay gear is one of the hardest working parts in the gearbox. If you're going to rebuild the box anyway, it's a good idea to replace the laygear since it's has pitting. If it has an anomaly, it can wear out other gears since it's in contact with them continuously.

It's worth an extra $150 or so just for the peace of mind to replace it, IMHO.

Let us know . . .

 

[NickMorgan]

It would certainly be cheaper to have the layshaft replaced now rather than discover that it needs to be replaced in a year or so.
A rebuilt gearbox from Rimmer Brothers in the UK is £286 (about $430, I think). You can have an overdrive and gearbox for £550 ($830). Unfortunately, they require an exchange unit or you would have to pay a surcharge plus shipping, so this is probably not an option for you, but it gives you an idea of prices.

 

[Mark Jones]

Mike,

I'd contact John Esposito at Quantum Mechanics, Munroe, CT. I had very good luck when I dealt with him concerning my MGBGT's overdrive gearbox.

 

[kodanja]

Johns the best!!

 

[71MKIV]

FWIW, in reading the news today,

The British Pound is taking a nose dive,

Give it a day or two, then talk to Rimmer again.

 

[NickMorgan]

Yes, just checked the latest conversion rate and the overdrive box is down to $808 now!!!

 

[Andrew Mace]

Nigel's part probably refers to the single rail gearbox found in MKIII GT6s. It may not work in the earlier, two-rail boxes found in MK1s and MKIIs. Andrew, can you confirm this??

Mark, I can/will double-check my parts books later today, but I'm pretty sure all GT6 boxes are essentially identical three-rail units. I do remember something about reverse being slightly different (ratio) in late MkIII boxes, though. The single-rail gearbox came later, for the Spitfire and TR7, and I think the TR7s ratios might be similar to that of the GT6; again, I can confirm/correct that tonight, unless someone beats me to it!

 

[19_again]

I got word from Spitbits that the laygear for the 70 is no longer available, same story from VB. The pitting is really minor, but it is there and he felt justified in recommending replacement. my concern in picking up a used gearbox is that this tranny is in fine shape except for the few teeth that spent 20 years in the air. I don't imagine I'd find anything different from anyone else given the age and specificity of this set of gears. Any used gear I would expect to come with the standard caveat, in fact I'd suspect any that didn't, and then I'd have shipping and probably more of what I already have. As for expertise, these guys are quite good and one of the techs happens to have a gt6 mark 3 sitting outside the garage waiting for the time to wrap it up, so they have taken an interest in my job just by osmosis. The alternative of cleaning it up as best as possible, using redline and "grownup" shifting practices may be good enough. As for Rimmer, I fear that if I wait 3 more months the price will be even lower. Good for me, bad for the world.
All that said, I'll gladly wait for Andy to come up with his answer.

 

[RonMacPherson]

Don't forget you always have the option of having that laygear welded up and ground down by a competent machine shop/gearmaker....

 

[19_again]

Yes I imagine I could bring it to a good shop and ask if they could make it better or just different. are the tech specs available somewhere?

 

[Andrew Mace]

...All that said, I'll gladly wait for Andy to come up with his answer.

Not a whole lot more light can I shed, except that the part numbers for all the gears seem to have changed between GT6 and + and the MkIII gearbox! Ratios, except for reverse, seem to have remained the same, though. Sigh...only Triumph (Leyland?) would do such a thing....

 

[Deleted member 8284]

I'm out of my depth here, but if this gear is tough/impossible to find new, and the issue is really only concern over potential damage to the case hardening, why not simply re-harden?

 

[TR_Jim]

If I rememebr correctly the pitch of the gears were different from the MKi and GT6+ and the later models. When I needed 2nd gear for the rebuild of my MKI gearbox, it too was 'unavailable'. Nigel at Spitbits found me a used one at a good price. Though used, he said he does not sell garbage, and he was right. It would be had to tell the used gear he sent me from new. I would ask Nigel if any good used laygears are available.