can you add overdrive?

I've been "hovering" around this forum for a few months now, timidly deciding how extensive I wanted my first care rebuild to be...
Well, I'm doing it! I've got the interior ripped out, and decided it was as good a time as any to just take everything off the body and get it painted! Arrgh!!!

Actually, it's going real well so far. However, when I pulled the cover off over the transmission area, there appears to be quite a bit of oil sitting on parts of the transmission. I guess I'm in for some work there!

My question is, can an overdrive unit be added to an existing transmission, or is this something that goes beyond practicality?

Thanks in advance for your help!

Yes, it's quite possible to add overdrive to your TR6. I just did it to a '70 GT6 and really enjoy it. Without it, driving on interstate highways was unpleasant due to the low gearing (3.89:1) on my car. Now, it's a breeze, plus the Laycock J type (correct for your car) effectively provides a six speed gearbox.

I might suggest, however, not to install the overdrive gearbox unless you intend to keep the car for the long term. It's a relatively expensive addition and can be quite a bit of work, even if you have the tools and skills to do it yourself.

There is a member here who has just completed an overdrive conversion to a '70(?) TR6, I'm sure he'll inform you of his experiences.

Welcome to the forum, please keep us informed of your restoration progress!

Bill--Yes, you can use your existing gearbox IF you replace the mainshaft, drill the top cover for the interlock switches, and swap the existing rear extension with the O/D bits. You will also need the O/D electrical harness, column switch, interlock switches, and relay. Unless you are experienced in this modification, suggest you find someone who is to do the conversion. For more information, visit the Buckeye Triumphs website under "Technical".

Alternatively, you can buy the whole affair from ebaY or John Esposito at Quantum Mechanics in Connecticut. This is an expensive modification ($1,700 - $2,100 for the bits alone). Since you have a '72, look for the A-type to mate with the existing mounts. I have an Esposito A-type with Volvo's 28% (v. 22%) reduction and was an excellent upgrade. Good luck!

Rick O.
72 TR6

Or for something completely different...

https://www.blindmoosefab.com/hvda.htm

No personal experience, but Herman has an excellent reputation.

As noted, one criterion is how long you will keep the car. Another is what type of driving you plan on doing. If lots of high-speed long-distance then OD may make that more enjoyable. I only take a couple of 500+ mile trips per year, most of my driving is around town and on club runs in the deserts & mountains... so for me OD wasn't a priority.

Wow.... $2,000...

Geez, this is going to be my first rebuild, and I'm already scared of the cost....
Maybe I'll just clean up this trans for now. This is supposed to be a fun car for some weekend runs, and it may not justify the cost...
That's an interesting link for the 5 speed Toyota trans.

Thanks for the info... I'll keep you posted!

Hey Bill
I just installed an Overdrive into my car last week. If you really want an overdrive you should be looking for a cheap rusted out tr6 or tr4 with an overdrive that is cheap and if you get a whole car you will also have the whole wire diagram and everything you need as long as no ones screwed with the car before. Looking for an overdrive car that is junk you might have to wait a while to find one. It was pretty easy for me to take my old tranny out b/c my interior isn't done yet but taking the seats, carpet, and tranny cover out isn't that big of deal for you if you really want the overdrive in your car.

I have a few questions about overdrive to. LAYCOCK DE NORMANVILLE! That's fun to say, isn't it?

But back to my questions. First, can anyone give me a rough idea of how much it costs to add an OD to a Triumph? Also, do the OD increase the top speed of the car? I can't see how it wouldn't, by cruising at the same speed but lower RPMs.