View Full Version : Overdrive Or 5 speed?

02-01-2007, 10:14 AM
I have an opertunity to either put a 5 speed conversion kit or an Type A overdrive ( Rebuilt )into a 1964 TR4. Cost will be roughly the same. Opinions Please. I am trying to choose.

02-01-2007, 11:08 AM
I believe this is an originality vs. personal preference/drivability issue only you can determine.

Paul Johnson
02-01-2007, 11:22 AM
I like the overdrive, because you in town you can leave it in 3rd, flicking back and forth between normal/overdrive. Works great for city use.

Simon TR4a
02-01-2007, 11:26 AM
I also like the overdrive, and as pointed out, this enhances the value of the car as it was a factory option.
My overdrive was rebuilt along with the transmission when I bought the car 10 years ago and has survived a lot of hard use, but a modern 5 speed would likely be more durable and cheaper to service in the (very) long run.

02-01-2007, 11:28 AM
I have just recently had a 5 Speed Ford type 9 transmission installed in my 71' TR6, I love ithttps://www.quantumechanics.com/categories.php?op=newindex&catid=17

<span style="color: #3333FF"><span style='font-size: 14pt'>I had a 73' GT6 with the electronic overdrive it was Great when it worked...</span></span>

02-01-2007, 11:53 AM
As others have said, it depends on if you are concerned about originality or driveability. In a TR4, I think you would be better off going the original overdrive route. 4 cylinder TR transmissions have a reasonable service history and have proven to be durable over the years. If you had a six cylinder TR (TR5, TR250 or TR6), then my answer might be different. The TR transmissions don't hold up that well with the increased torque of the six cylinder as the rear layshaft (countershaft for us 'mericans) bearings tend to fail due to the high torque applied when in 1st and 2nd gear. For this reason, the Toyo 5 speed is a good choice for a driven TR6. Another option for six cylinder cars is to have the layshaft gear machined and add a 2nd rear bearing, effectively doubling the capacity and increasing the longetivity of the transmission. I have an overdrive in my TR6, MGB GT and the Herald and I like them. Six forward speeds is a nice feature as I frequently run 3rd and 3rd overdrive when running through twisty turns.

02-01-2007, 12:08 PM
Needless-to-say, I am a fan of the Toyota 5-speed. It's not an originality issue as it is completely reversible bolt-in mod (I kept all the original replaced parts.) It also uses the original shift lever so unless you crawl under the car to see the gearbox, you will never detect the change. Clutch action is precise and smooth, no adjustment or slave issues (doesn't use one) that I hear about frequently. The only downside of the HVDA kit that I've seen so far is that the Hydraulic T/O bearing is not DOT5 compatible so you can't use silicone hydraulic fluid in the clutch M/C.
I personally can't see the need to flick through gears unless you like in a very hilly area. I've got plenty of torque in any gear at any rpm with 5-speeds. I admit to not ever driving the TR overdrive so my comparison is one-sided.

02-01-2007, 01:03 PM
I'd prefer the O/D. I recently found one for TS1203LO but I had to buy another car to get the one that was laying in the trunk.

For me, It's both an issue of originality and the fact that I like British cars to be British....of course de Normanville was an American transmission designer, if I remember correctly!

The basic design has gone on to be used in the much-heralded Gearvendors Overdrive units that now are in wide use in tow vehicles, hot rods, etc. A tuff unit that can take over 1000 HP.

02-01-2007, 06:24 PM
I've driven both and I have the 5-speed. If I had a near stock car though I'd have the o/d in a heartbeat.

02-01-2007, 07:19 PM

This is very much an issue of personal preference and, perhaps, driving style.

The modern 5-speeds are pretty widely available and easily adapted. They will make highway driving more pleasant.

For more "sprited" driving on twisty, windy roads the overdrive is hard to beat since it effectively gives a close ratio 6- or 7-speed gearbox (depends upon model and setup... on the earlier cars they OD was usable on 2nd gear, it was not on the later cars. All offered OD on 3rd & 4th. It is possible to set up 2nd gear OD on the later cars, though, if wished.)

With the various possible 5-speeds there are some gearing choices to make. With the OD, it can be set up to provide 22.5, 25 or 28% reduction.

Some 5-speeds might weigh in a little less than the TR gearbox combined with OD (approx. 125 lbs). If any vintage racing is planned with the car, the OD adds significant weight, but a modern 5-speed might be prohibited by the sanctioning organization.

Happy shopping!

02-01-2007, 08:43 PM
Love my "6" w/overdrive.

If it went down, though, I would install a modern 5 speed in a heartbeat.

Would also replace the rear universals with CV joints, the rear drums with discs, the engine driven fan with electric (oops, already did that), Strombergs with mass airflow FI, well..you get the idea.


02-01-2007, 08:54 PM
I went with the Quantum Mechanics built "J" type, which is proper for my TR6 and like Paul Johnson above, love driving it. I think that you may have an advantage over ours, as you'll have O/D in 2nd gear as well with the "A" type.

I have a buddy in CT with one of those "A" types all rebuilt, sitting in the crate it was shipped in on, doing absolutely nothing, since he sold his restoration project and bought a BMW Z-4.

Big waste.......

02-02-2007, 09:18 AM
I guess I should weigh in as an HVDA owner.

I love it, but for me the option was either the HVDA or try to find an Overdrive Transmission. Availability was the deciding factor.

Geo Hahn
02-02-2007, 04:57 PM
I just put an OD from Quantum Mech in the TR4 -- since the car is stock and mostly original (incl paint & interior) I didn't want to stray too far from a true TR set-up.

It's just great... but then if I had put in a Toyota 5-Speed I would probably think that was great too.

02-02-2007, 05:51 PM
I have an opertunity to either put a 5 speed conversion kit or an Type A overdrive ( Rebuilt )into a 1964 TR4. Cost will be roughly the same. Opinions Please. I am trying to choose.

My take on this, is that if the cost is about the same, then go for the original TR OD unit, especially due to the fact that it is an "A" unit. John from Quantum Mechanics (https://www.quantumechanics.com/) was down at the Long Island Triumph Associations Saturday tech session last week, and showed us all of the differences in the "A" and "J" units. You wouldn't believe how much smaller the "J" unit OD clutch and other parts are. His contention is, that if the proper oil and maintenence is performed in the TR OD unit, it should last 50-70k miles. He also sells the Sierra 5-speed unit, which he says is very good. He brought the kit down with him, and it looked very complete and robust. I asked him about the Toyota five speed conversion, as that's what I'm putting into my TR3. He said that it's basically a good kit, and every W58 Toyota trans he pulled apart, he just cleaned things up and put back together. I'm putting in the Toyota conversion only because it is going to cost me considerably less money then putting in an original TR w/OD, because my original tranny is a four speed. If I had the choice that you have, go for the TR w/OD...that's assuming that the TR trans is recently rebuilt by somebody like John at Quantum.

02-02-2007, 06:30 PM
I have the Triumph 4-speed with J-type overdrive unit that John Esposito did for me. I use the overdrive for highway use only. It is awfully convenient to slow down for an upcoming traffic jamb or traffic light with the flick of my left pinky finger. I try my best to be kind to my transmission, only rarely putting it to the test. I like my setup very much, recommend Quantum to the highest level.

02-02-2007, 07:10 PM
Last fall, we had great runs of about 60 miles each day of a weekend through the back roads of Cape Cod and another couple of weekend days in MA/RI in the wine country. There is nothing better than running with 50 British cars around hilly back roads in 3rd gear and flipping the switch in and out of O/D while everyone else is up and down shifting. Those units are sweet..........

02-02-2007, 07:16 PM
John at Quantum also installed my Ford Sierra 5-speed unit.

This unit is fantastic in my 71' Tr6, along with the webbers John installed, the car is basiclly trouble free.

John is the most knowledgable fellow in these matters I have every met.


02-02-2007, 09:31 PM
Another problem to consider is the cost of buying a supposedly good "A" or "J" type overdrive and finding it doesn't work once installed. The only option is to drive the car as a four speed or have the car down for a longer period for a complete overdrive rebuild. A good rebuild will cost a grand and half plus shipping so you end up putting a lot of money into a project that should have made more sense with a Five speed.

The average British Car owner does not understand how the accumulator works in the "A" version, adjustment of the solenoids etc on either type and could end up with $2K of money in the initial purchase. This will drive a person crazy and could cause him to drop his love for the marque. That said, If you are not mechanically inclined put a known good Five Speed Kit in the car and you will love it.

The British Car Forum Senior members should do their best to educate Junior members to help prevent this type of tragic result and their car becoming a money pit.

This subject is close to me because 7 years ago I trusted an overdrive purchase I made for converting a non-overdrive TR6 I owned. I got so ticked from the bad experiences that I sold it and regretted it later. Especially when the idea of 5 Speed Coversions came about later on.

Good Luck and but be smart about it.

1959 TR3 Restored 2001
1972 TR6 In Restoration

02-02-2007, 09:58 PM
That's a specious argument - its like saying all 5-speed conversions are bad because I bought a dodgy gbox from a breakers yard once.

I paid $2500 for a kit plus a remanufactured w58 gearbox that leaked oil like crazy when it was installed. It had to be pulled after it was put in, and a new seal fitted before it was ok. I looked at the overdrive conversion, and the cost was about the same. It would have probably worked perfectly, but I needed a 5-speed.

Did that sour me on 5-speeds conversions? No, it's still in there. Do I think the overdrive is a better option unless you have a reason for not putting it in? Yes - mainly because imo it's more "fun" to drive, and it preserves the value.

If you want to build a monster fire breathing TR6 it won't work - it can't handle the power, but then the diff and the halfshafts won't either; otherwise it's just fine.

02-06-2007, 11:35 AM
Thank you all, for your comments. On balance and after much research I am going with the rebuilt A type OD & transmission as a unit from Quantum Mechanics. I will have a local British car Mech. install it so it should go well. Again, Thanks to you all and Happy Triumph motoring to you.

02-06-2007, 11:42 AM
P.S How would you describe a monster fire breathing TR6? What kind of HP are we talking about? My TR4 dynos at 115 HP with 135 Ft lbs tourgue. Only modification is 87 mm pistons and I went to SU carbs with Petronix ing.

02-06-2007, 12:30 PM
P.S How would you describe a monster fire breathing TR6? What kind of HP are we talking about? My TR4 dynos at 115 HP with 135 Ft lbs tourgue. Only modification is 87 mm pistons and I went to SU carbs with Petronix ing.

New-off-the-showroom-floor especially the later de-tuned TR6's were little better, if any, than the TR4's. In fact the power to weight ratio might have not been as good.

Remember that the 1970's were the years of the Noids, as in paranoids. And the government restrictions on vehicles became a smothering mess.

The potential difference becomes more obvious when rebuilding and at somewhat comparable build levels from the Paeco charts the four has about 75% to 80% of the power of the six. Which I feel is still impressive.

Geo Hahn
02-06-2007, 01:10 PM
...I am going with the rebuilt A type OD & transmission as a unit from Quantum Mechanics...

FYI - I just put one of John's Type A's in over Christmas. Very nice except it was very difficult shifting into 2nd. I mean almost impossible.

John said to give it time as it was probably just that the new synchro would need some miles/shifts to break in.

Somehow I managed to put 1,000 miles on it in January w/o even leaving town -- as John predicted it was shifting much better after 500 miles and is just great now.

I just pass this along in case you encounter something similar.

My only regret here is that I waited so long before doing this.

02-06-2007, 04:08 PM
i have the same dilemma. i have an a-series overdrive that needs rebuilding, but as some of you know, i am aiming for 145hp, 148 ft-lbs torque. can the early gearbox and tranny take the power. NOTE:this is the early thin bell housing. I am very mechanically inclined and am not afraid of doing the rebuild myself or doing a supra 5-spd conversion. i like the originality that really makes it british but i don't want to do a tear down every 2 years. (mostly road driving).

02-06-2007, 05:43 PM
The boxes are supposed to be good up to about 200hp.
At that point you want to be taking a close look at your diff and halfshafts too.

02-06-2007, 06:53 PM
the toyota will take more than 200 but its' the triumph gearbox that i wouild like to use if its' strong enough. according to Kastner and Piggot, i'd be on the edge of reliability. anyone with 150hp with the early gearbox had any problems because of strength?

02-06-2007, 08:15 PM
I *meant* the triumph box - the Toyota W58 is good over 350...

02-06-2007, 08:56 PM
OK - here's my TR6 O/D 'war story'. About 10 years ago a guy sold me a g/box and A-type OD pulled from a scrap car for $750. Had to replace the side cover that the solenoid mounts to - it's vulnerable to breakage when it's off the car. Not too much of a problem since it was available from VB. Also had to buy the speedo angle drive, longer speedo cable (I think), the electrical harness, and switch. The disappointment was that the gearbox was done for - one of the gears up front was was mostly ground away (I think it was the gear on the layshaft that engages with the gear on the input shaft). The gearbox I was taking out was already noisy, and I wasn't going to attempt stripping it down, trying to switch the output shafts, etc. So I used the dead gearbox as the exchange one for a rebuilt one from Rimmers in UK. As I recall the shipping to the US was very low (free special even??) - sending the exchange back was $$ though. I went through and changed some parts in the overdrive- the accumulator o-rings seem to stick in my mind. 10 years and probably 30k later I have been happy with it. It does leak, I should have changed the tail shaft seal, and I think it is oozing at the joints between g/b and o/d. As far as being hard to get into second, the old one and new one have been the same way- only an issue for about the first 5 minutes in the cold. As far as all up $$ - I think all together it was around $2000- more than I had planned on, but I do think it adds a lot to the car. People are looking for it when they're TR6 shopping, for sure. Good luck with the new one.. - Pete