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Triumph TR6 - Overdrive question

I Have a 74 4-speed. If I can find a J overdrive, what else I need for the installation other than the switches.
Do I need to change the trans' main shaft? Do I need to change the drive shaft?
Paddy Kan

Hello Paddy,

I routinely sell JTypes on ebay that I pull from Volvo transmissions.

To adapt the JType to the Triumph non-overdrive 4 speed you have to dismantle the transmission and replace the mainshaft. You need to find a JType adapter. The adapter is the aluminum casting that connects the JType to the gearbox. Price for the mainshaft and adpater runs around the $500 USD mark.

You need to drill the transmission cover plate and install the 1st, 2nd and reverse gear interlock switches.

A Volvo JType will need a Triumph drive shaft flange installed and some need the rear mounting holes drilled and tapped.

I have an article that goes into detail about the conversion process if your interested I can email to you.


John Parfitt
John Parfitt

John- How's the 5 speed?


The 5 speed conversion is an excellent piece of equipment and really transforms the car.

Ultimately I decided on the 5 speed over the overdrive for long term maintenance advantages and possibly to create a drive-line that could withstand higher horsepower.

In terms of installation: the 5 speed conversion was easy to install - any shade-tree mechanic can do it on a weekend. By comparison, converting a non-overdrive Triumph to a J Type overdrive is a big deal and prolly need a pro since the tranny needs to come appart etc.

I think for those who are concerned about resale value and originality, the J Type is the way to go.

For pure performance, spare parts availability and ease of repairs, the 5 speed conversion is the way to go.

One other thing about the 5 speed conversion - I solved a clutch issue by installing the optional hydraulic throwout bearing thus eliminating the troublesome cross-shaft and fork mechanism.

On balance, the 5 speed conversion really transforms the TR6 into something with a much more refined clutch and gearbox driveability.

John Parfitt

Paddy-Last month on the 6packlist, there was a lot of discussion about group purchasing J type od units from Volvos and all the bits and pieces for the conversion. You might try contacting this person for more info-Don
Berry Price
BTP Price

thanks, Berry
but the email address won't work
Paddy Kan

what I mean is , the email bounced back.
Paddy Kan

Paddy-Sorry, my mistake. Try
BTP Price

yes, please email me the article. Thank you.
Is it you listing a Volvo J OD on ebay?
Paddy Kan

Hey John:
I'd like to go the Volvo transmission route as well. Are the J types fairly common from the Volvo? And what about using a Stag or 2000/2500 transmission? I already have a spare Triumph 4 speed and would like to put an OD in the 6 again.

Paddy / Bryn,

Yes - that's me selling the J Type. The J Types are very common on the Volvo's although, the cost of the J Type is a small percentage of the overall cost of doing the conversion.

I you are paying someone else to do the work the cost will be like a transmission rebuild plus the cost of the J Type, new mainshaft and adapter. Add to that the electronics involved plus installation in the car and it gets expensive.

I think the Stagg 4 speed will work although I must confess having never owned or worked on a Stagg so you better do your own research on that question.

John Parfitt

The Stag gearbox doesn't fit the TR6, it has a different input shaft, but if you can find a Stag/late 2500 or Dolomite Sprint you will get all the bits you need to do the conversion ie mainshaft, adapter, switches etc, but you also need to have a late [post '74?] TR6 gearbox it isn't so easy with the earlier boxes.
R. Algie

This thread was discussed between 26/01/2005 and 02/02/2005

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