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Upgrading Triumph 2500/2000 Gerbox


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Apologies if this seems like a very basic question.

At some time in it's life my 1970 TR6 has been fitted with a Triumph 2000/2500 A type overdrive gearbox.

The gearbox itself is in excellent condition so I am reluctant to swop it for a genuine TR version.

Is it possible to convert my existing box to TR specification?  I know the output shaft is thicker and the ovedrive solenoid is vertical instead of horizontal.

Can you buy the required parts and can anyone recommend someone to do the work for me please?  I am currently based in Leamington Spa.

 

Many thanks

Steve

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2 minutes ago, SteveMXC said:

Apologies if this seems like a very basic question.

At some time in it's life my 1970 TR6 has been fitted with a Triumph 2000/2500 A type overdrive gearbox.

The gearbox itself is in excellent condition so I am reluctant to swop it for a genuine TR version.

Is it possible to convert my existing box to TR specification?  I know the output shaft is thicker and the ovedrive solenoid is vertical instead of horizontal.

Can you buy the required parts and can anyone recommend someone to do the work for me please?  I am currently based in Leamington Spa.

 

Many thanks

Steve

ORS In Sheffield would be your best bet as they have all the bits to do it. https://www.overdrive-repairs.co.uk/

Stuart.

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Isn’t Mike Papworth based somewhere near Leamington Spa ?

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7 hours ago, stuart said:

ORS In Sheffield would be your best bet as they have all the bits to do it. https://www.overdrive-repairs.co.uk/

Stuart.

+1 Bruce They know the TR range of gearbox's back to front and mods to make it more reliable plus they have a Laycock test rig to check the operation of the O/D and they make a lot of the replacement parts as they have all the Laycock drawings and machines. I used them 3 years ago to overhaul my transmission and I am well satisfied.

Bruce.

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10 hours ago, SteveMXC said:

Apologies if this seems like a very basic question.

At some time in it's life my 1970 TR6 has been fitted with a Triumph 2000/2500 A type overdrive gearbox.

The gearbox itself is in excellent condition so I am reluctant to swop it for a genuine TR version.

Is it possible to convert my existing box to TR specification?  I know the output shaft is thicker and the ovedrive solenoid is vertical instead of horizontal.

Can you buy the required parts and can anyone recommend someone to do the work for me please?  I am currently based in Leamington Spa.

 

Many thanks

Steve

I am just finished building a 2500 box with J type overdrive as a spare for my TR6 and can advise on a couple of things.

The 2500 and the TR6 gearbox are essentially the same. The input shaft being the only significant difference and all that means is you use a 2500 clutch plate. I understand there are other more common Isuzu or whatever plates that also fit.

The output shafts are the same, depending on whether you have overdrive or not. The output flange is different but as the box is in your car already that has been swapped for a TR6 one or the 2500 one has already been modified.

The overdrive solenoid is vertical on A type overdrives, which is what your 1970 car would have been built with if it had overdrive originally. The horizontal solenoid is on J type overdrives which were fitted to later TR6s and 2500s.

You car with a 2500 gearbox and A type overdrive is essentially exactly the same as a TR6 gearbox and overdrive, bar the input shaft which is not an issue.

If it works, don't touch it.

 

Edited by John McCormack
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Hi Steve,

 

I'm with John, above, here.

Why would you do anything to the box, if currently its fine?

Leave it alone, when and if it fails, then is the time to sort, but we have saloon boxes in Cumbria group,

that have done many miles having been in cars 20 years plus.

John.

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The mainshaft front spigot dimension changed at some point on the later gearboxes, so you would need that dimension to get the right input shaft and bearing, I think, may be wrong?

John

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There is little point changing the input shaft to TR6 spec - all you achieve is a different spline for the clutch. Never clear why Triumph used different splines for the TRs to the saloons as it's neither an upgrade or a downgrade.

Were you thinking more of upgrading the box to Stag spec which had different layshaft bearings?

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I have 2 non OD TR gearboxes which I really don't want to fit to my restoration, recently bought, as a spur of the moment thing because I just came across it, a saloon J type OD box. I haven't done a lot of research specifically on this as yet but I understand that the input shaft diameter on the TR and saloon boxes is different (haven't checked tbh, will do now). So my thought was to change the I/P shaft to TR and use the saloon box (OD), probably overhauled, I assumed that the TR box could take more torque and hence had a larger shaft and bearings, you reckon there is no improvement in that respect over saloon spec in the TR box? I am going to be doing some engine work on this and fitting an LSD so o ideally I'd take whatever low hanging fruit there is in terms of drive train upgrade, without going nuts as in I want to use as close to an original box as I can.

Edited by TRier
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Hi there,

No mainshaft overdrive to non overdrive are completely different, rather to prove the point a non overdrive mainshaft is worth about £10,

and overdrive manishaft is around £200.

I think if you are thinking of putting a lot through your transmission, it is a TR type overdrive you need first rather than a saloon, and then the gearbox.

Personally I use it till it broke and then fix upgrade as you wish.

John.

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+1 "Personally I use it till it broke and then fix upgrade as you wish".

I have a 2000 gearbox fitted with a type A overdrive 30+ years ago-when there was a lot of expertise in the Australian auto industry in modifying Triumphs. I'd need to do a lot of research to be confident in changing this set up now.

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Thanks guys, you know what I think as advised I’ll keep it simple and go with what I’ve got and the saloon clutch plate and see how it goes, it’s not a mega task to take the box out and do an upgrade later if it looks like failing. I”ll open the box and take a quick look and if it looks OK just run with it. The box wasn’t expensive as they go.

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On 11/22/2021 at 7:59 PM, TRier said:

Can you take the input shaft from a non overdrive TR box and fit it to a saloon J type OD box or do you need to have a conversion shaft so to speak?

The input shafts are tricky. There are a number of different versions in length and the gear helix.

Once you have found one the same length as the existing one you need to ensure that the gear helix is the same as your mainshaft gear. They have the same number of teeth but the angle of the teeth is different. I know because in my 1st attempt the laygear wouldn't mesh with the mainshaft. Wrong helix.

 

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On 11/23/2021 at 7:39 AM, John Morrison said:

Hi there,

No mainshaft overdrive to non overdrive are completely different, rather to prove the point a non overdrive mainshaft is worth about £10,

and overdrive manishaft is around £200.

I think if you are thinking of putting a lot through your transmission, it is a TR type overdrive you need first rather than a saloon, and then the gearbox.

Personally I use it till it broke and then fix upgrade as you wish.

John.

The overdrives are the same between saloon and TR6 except for the final ratio which varied depending on the car it went into. From memory you can get 23, 25 and 28% overdrives. Most J types here seem to be the 28% version.

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2 hours ago, John Morrison said:

Hi John.

My thinking was that the saloon typr overdrive , certainly A type is weaker thatn the TR one.

TR has 8 springs , saloon only 4 springs.

John.

I must admit my knowledge of the A type isn't great and is based on the TR2s I own. I wasn't aware of any difference between the two with respect to the 4 cyl TRs.

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