TR6 Do the HVDA [Toyota overdrive conversion] or repair my existing J Overdrive?

What might you do and why?

What have you done and how has it worked for you?

I bought a J overdrive from Down Under. You might guess the seller. It went in-op. Mechanic looked at it and said: "I'm not sure what is wrong with it, but the pump could be bad." I respect this mechanic. Further he says: "I recommend the Toyota ((Herman van den Akker, I suppose) overdrive/transmission conversion."

His thoughts are it would be more reliable in the long run.

That said, I have not tackled trouble-shooting on my own with help from the Forum my existing J overdrive. Yet another mechanic, which I may have mentioned already in another thread, attempted repair on the overdrive, and left me with it still in-op and a nest of wires laying all over my transmission.

I have read comment from at least one guy (Bloke, British politically correct version,) who said he did the conversion and got little to no reduction in
freeway rpm's. Frightening thought.

My objective is to relax the engine, save fuel and have it be reliable for daily driving.

I am torn, because I dream of having the existing overdrive working as it should because I like the flexibility of shifting as it does in third as well as fourth gears, and, I have read rumor of very cool setup from a Stag shifter with push button operation. Very cool, in my view.

So what do you think? What has been your experience?

Taking a look at what I have, to some degree, does make sense. It seems most guys' attitudes are to leave the overdrive and transmission stuff to the Pros. What do you think? Oh, and by the way, this is an add-on. My car came stock with a four-speed.

Don't give up or be intimidated by the J type OD. Work through the trouble shooting guide (and other sections) on the Buckeye site: https://www.buckeyetriumphs.org/technical/jod/JOD4/JOD4.htm
Berry

Well, let me put it this way. I have currently have 3 Triumphs and they all have Laycock overdrives in them. Herman once offered to sell me one of his kits cheap (in return for using my car as a test bed) and I turned him down. Even Herman didn't put one in his own car, until people got to ragging him about not practicing what he preached!

IMO, the J-type OD is simple and robust (for what it does). The same basic design is still in use today (see Gear Vendors) and they are not difficult to troubleshoot and rebuild (although there are some special tools that you will need to make or buy). All of the active components are readily available used, since the same OD was used in Volvos and other cars. (However, there are some TR6 specific bits in the adapter and mainshaft, etc.)

But, again IMO, 3rd OD is nearly useless with a J-type. It's almost the same ratio as 4th direct, and the J-type shifts slow enough that you can shift just as quickly into 4th direct (or 3rd direct) with the clutch.

The comment about "little or no reduction" makes no sense at all to me. The reduction is not huge, but it is clearly another gear, with either the Toyota conversion or the J-type. Once you've gotten used to driving around in 5th (or 4th OD), 4th direct will seem like driving in 3rd gear does now.

Best part about the conversion, IMO, is that if it does break, you just throw it away and buy another one.

I will share 2 sides to this coin.
Have a good friend who is local and put one of Hermans setup in his 3B. Works great and he is totally happy with it.
I have a 3A that came from the factory with the 4:11 and OD.
At time of restoration had the OD and tranny gone thru. Tranny worked great...but the OD did not.
Struggled with this for 2 years. Finally took it to the folks at the British Car place in Stockton CA.
Wonderfull! Has worked flawlessly since. Probably two sides to this also...but think may be good that I kept the OD at resale time . Love it. Gil NoCal

From Dennis

who said he did the conversion and got little to no reduction in
freeway rpm's. Frightening thought.

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From Randall

The comment about "little or no reduction" makes no sense at all to me

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Randall I read the first quote as "No difference between the J OD and the HVDA.
Not OD vs no OD

I could be wrong though

DNK said:

Randall I read the first quote as "No difference between the J OD and the HVDA.
Not OD vs no OD

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Oh, OK. That's reasonable. As I recall, there is a choice of several different ratios with the HVDA conversion, but they are all pretty close if not identical to the ratio with the J type. Even the J type & A type aren't exactly the same, but you aren't likely to notice the difference between the two.

A friend of mine was complaining that he couldn't tell the difference when engaging the overdrive; turned out he had an electrical short that was leaving it engaged all the time in 2nd, 3rd & 4th.

TR3driver said:

...A friend of mine was complaining that he couldn't tell the difference when engaging the overdrive; turned out he had an electrical short that was leaving it engaged all the time in 2nd, 3rd & 4th.

Click to expand...

Uh, that would just be uh...drive

2Wrench.. I've got both. HVDA in my 62 TR3b and J type in my 67 Tr4a. I put the HVDA in myself and it was not to difficult. The only problem I have with it is a pressure build up that blows the rear seal. This has happened on a few occasions and not always at the best of times. It seems to be a common problem with Toyota tranny because there is no pressure release valve. Herman and I have talked about this for awhile and the solution seems to be to drill a small hole to let the pressure out. I have done this and will await this season of driving to see if it worked. Now you would like to know which one you should go with? I like them both. The only real problem is getting used to the shift between the two cars. You sometimes forget where you are and try to throw the shift into fifth and it won't go. It happens. My BCTR buddy has a TR6 PI with the J type and the buttons on the nob of the stick and its a pretty fast and cool ride. Flip a coin cause that's where your at in my opinion.

I think you need to ask
Do you like the oil drips under the tranny ...or not!

Or, you could be way-radical and just drive the car as a 4-speed, the way many (most?) TR-series cars were delivered to the USA. Unless you do a couple of hundred miles per week, the cost of either the HVDA conversion or the J-type fix might not be worth spending. Despite the conventional wisdom, not every TR on the planet has to have overdrive, wire wheels, and a hardtop..dare we call these Stepford-cars?

If, however, you go the J-type route, find somebody competent to convert the transmission top to allow overdrive operation in second gear. Overdrive-3rd is, as stated above, pretty useless...but overdrive-2nd. is wonderful for twisty uphill roads (canyons, etc.)

The switch on the knob looks cool -- but when I want to engage (or disengage) overdrive my right hand is on the steering wheel, not the knob.

With the original stalk switch I engage/disengage with the flick of a finger, if the switch were on the shift knob I'd have to reach down each time. Since a lot of this action is on twisty mountain roads I think I would find the knob switch a bother (though admittedly I have never driven with one).

I agree with George..I don't want to have to drive with one hand when I'm engaging and disengaging the OD.
What I did do is loosen the ferule and rotate the OD column switch so that I flick it forward to engage. I did dog leg bend the stalk to make it closer to the steering wheel, within "flicking" distance so to speak.

2W,
I think either way is fine. My car is a 4 speed and if for no other reason than to do something nice for my car I plan to go with the HVDA conversion one of these days.
Improvements are in the eye of the beholder. I like tinkering with my car. I don't do anything that cannot be undone.
I use Mobil 1 engine oil and Redline in the transmission. Overkill? More expensive than necessary? Probably but they make me feel good.
I doubt that many TR owners use their cars as the daily driver. Mine is a Toy/Hobby. IMO gas mileage is not the objective. You could go with the HVDA conversion and store the factory transmission and OD. If you decide you don't like the conversion repair the OD, remove the HVDA and sell it. The only real problem is money and of course sneaking it under the radar of The Battleship. Unlike greens fees, single malt scotch or a toupee there is always decent residual value in whatever you do as long as it's not over the top.

PS: I have a hardtop because I like it. No wire wheels because I don't care for them.

Bob, on this side of the world I would do the Dupont change

I appreciate all comments, and I've got to tell 'ya, I am driven (okay, yeah, pun intended,) by cost effectiveness. It seems possible that I could find the problem and maybe even repair it myself and it would be cheaper. So I've been referred to Buckeye, and while it seems overwhelming, I think I will just take everything slowly, go one step at a time and see what I can do. It seems the parts are not so expensive, it's the labor that makes it so. So, I suppose you'll be hearing from me from time to time, as I begin yet
another adventure. Thanks to all for looking in, and just know, that sometimes I'm slow, because, unfortunately, I still have to work. Dang.
PS. If I get in over my head, I may have to go conversion. I'll start with a look at wiring and solenoid first, I suppose.

It will probably be cheaper to fix the one you have, there are shops around that can help. There are a couple 5 speed conversion options out there by the way.

2wrench said:

PS. If I get in over my head, I may have to go conversion. I'll start with a look at wiring and solenoid first, I suppose.

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Start with the simple stuff - is the solenoid working?

Eliminate the electrical problems- power to the sol.&the sol. itself,clogged filters- the easy stuff that doesn't require removing or disassembling the OD. The local Triumph club ( https://www.triumphtravelers.org/ ) would be good source of local brains to pick and tools to borrow. I think at a minimum you will need a wrench for the sol., a peg spanner wrench for the 3 plugs, and the pressure gauge. Note that the oring sizes for the sol. are given in the Buckeye article and can be purchased locally.
I think you will find the project a good learning experience as well as cost effective.
Berry

Dennis
I live in Brentwood I have the HVDA in my TR3 and love it. Never had OD. I am finishing up a TR250 with OD. If I OD in the Tr3 I most likely would have kept it. I am going to meet with a Triumph Guy this week, I have a ton of extra parts that I want to get rid of, and he has some TR250 rims that I need. He works on the OD trans and has done a couple of them for our group of Triumphs in Brentwood. If you would like send me a PM and I will give you his info.

poolboy said:

I agree with George..I don't want to have to drive with one hand when I'm engaging and disengaging the OD.
What I did do is loosen the ferule and rotate the OD column switch so that I flick it forward to engage. I did dog leg bend the stalk to make it closer to the steering wheel, within "flicking" distance so to speak.

Click to expand...

Paddle Shifter just like an F1 car eh?