TR2/3/3A tr3a overdrive vendor questions

[TFB]

My body is off the chasis and although the stock trans is rebuilt and installed, I have been thinking that if I want an overdrive now would be the time,before I put the body on.
Budget is tight,and have seen this vendor selling overdrives .I sent him a note asking if he pressure tests,but was wondering if anyone has bought one of his ovrdrvs and if there are any particulars I should ask about or be aware of if I decide to bid.

ebay tr-man tr3 overdrive
Thanks
Tom

 

[mallard]

Tom I have two of his OD units. One is in the TR6 and has worked perfect for four years now, and my original OD from my TR3 was rebuilt by him. I have not run the TR3 OD yet but I don't think I'll have any problems. I would use him again if needed.

Have you thought about any of the Toyota conversions available? One of the Forum venders sells a very nice setup for a great price. I will tell you that I'm friends with the vender but I have no money in the product. I driven some of his conversions and they work great.

 

[TR3driver]

Just something to be aware of: That is not a TR3 gearbox shown on eBay, but a mid-TR6 box. It can be made to fit your TR3A (I have a TR6 box in my TR3), but some small modifications are required. And it's really a PITA to get 3/4 of the way through an installation and find that you have to take it back apart because things don't fit right.

To my way of thinking, such an obvious "mistake" means there may be other mistakes not so obvious.

 

[TFB]

Thanks Kieth and Randall.
Randall,I seem to remember some of the issues you had from previous posts.I think it was related to longer length changing crossmember position and shifter hole by a slight amount.If I found a good deal local I would consider it,but would prefer the one that fits as stock.
What is the idenifying feature that told you mid tr6?
Thanks again
Tom

 

[TR3driver]

The circular bulge on the side marks it as a 4-synchro box while all TR3/A had 3-synchro. The thick flange at the top of the bellhousing marks it as not a TR4/A box. And late TR6 used a J-type OD.

It might be a TR5/250/early TR6, but ISTR they didn't look quite so beefy up front.

The other problems with fitting a TR6 box include longer studs in the engine, and some fiddling with the clutch slave (the thicker flange moves the slave mounting plate to the rear, which requires a shorter pushrod and makes the stock return spring too long).

Turns out the stud length is kind of critical; when I moved the TR6 box into my current TR3 I made new studs that turned out to be too long. I forget offhand where the interference was, but the gearbox wouldn't go into place until I shortened the studs by 1/4" or so. Maybe it was the output flange hitting the body. If you zoom in here https://i258.photobucket.com/albums/hh260/TR3driver/TS13571L/DSCF0023.jpg you can see my rather amateurish looking cut (done with the stud still in the engine and with the gearbox just a few inches away).

 

[TFB]

Thanks Randall.all seems pretty doable,especially since I have tub off.I guess I am most comcerned about the rear trans mount,and shifter to hole position.
Trans is ts37860,with bull nose starter so earlier flywheel. Is the clutch,pressure plate and throw out bearing assembly same for mid tr6 trans?
Are these issues the same for any full synchro ,tr3b,tr4 ,tr4a trans except for the thicker top bellhousing flange on the latest a type,the mid tr6?
And lastly,any advantages other than the sycro first to the latest a-type vs. converting my tr3a trans,beside fit?

Thanks
Tom

 

[TR3driver]

You should probably keep your old (type) of clutch, pressure plate & TOB. Likely the trans won't come with the TOB or carrier anyway. But to answer your question, no, they are not the same. The TOB & carrier need to match the pressure plate, which needs to match the clutch & flywheel. I originally kept the TR3A clutch, but later converted to a TR4A-6 type clutch since the alloy flywheel was only drilled for the later clutch (which is lighter anyway).

The rear mount and shifter location issues are the same for any 4-synchro box (TR4-TR6); the clutch slave problem only shows up with the later ones with the thicker flange. Forgot to mention before, you may need to drill the top cover to use the TR3 style shift lever; and you'll lose the gearbox dipstick. (I rebuilt my TR3A top cover to fit the TR6 gearbox, just to keep the dipstick.)

I wanted the thicker flange because I had a TR4 box (in a previous TR3A) that broke along the flange.

Don't recall offhand when the change was, but my TR6 box also has slightly closer gear ratios, which is a small advantage.

 

[DNK]

Is it possible to drill the top cover for a dip stick ,Randall.
Think that was asked before

 

[TR3driver]

Is it possible to drill the top cover for a dip stick ,Randall.

Others have said "Yes". I didn't try it myself, but don't recall why not. Might have been just because the TR6 cover wasn't drilled for the lockout switches (and I didn't have the right tap on hand).

 

[TFB]

Thanks again Randall.
did you have to slot the 2 bots for rear trans mount ,the 4 for the cross member ,or a little on all?
Also ,there are 2 ratios 22% and 28%?
How do you tell the differeance and is the 22% usually considered the most desirable?
Thanks
Tom

 

[TR4nut]

28% was not offered in TRs, possibly Healeys only I think. 22% is what you'll get unless you substitute the part. The 28% would lower cruising RPM or increase your speed but it doesn't do that much for you, for example:

3000 rpm 1:1 60 mph
3000 rpm 1.22:1 73 mph
3000 rpm 1.28:1 77 mph

 

[tdskip]

These guys are also an option;

https://www.quantumechanics.com/

 

[HerronScott]

You should probably keep your old (type) of clutch, pressure plate & TOB. Likely the trans won't come with the TOB or carrier anyway. But to answer your question, no, they are not the same. The TOB & carrier need to match the pressure plate, which needs to match the clutch & flywheel. I originally kept the TR3A clutch, but later converted to a TR4A-6 type clutch since the alloy flywheel was only drilled for the later clutch (which is lighter anyway).

Randall,

Isn't the front cover longer on the TR3-4 transmissions that used the older type clutch?

Scott

 

[TR3driver]

Yes, the front cover was slightly longer with the earlier clutch. But lots of folks have reported that the shorter cover works OK with the early clutch. The TR6 input shaft is also somewhat shorter, so it doesn't engage as far into the pilot bearing. Doesn't seem to be a problem.

On the rear mount, the only holes I modified were the two where the mount bolts to the cross member. I drilled two new holes each about 3/8" behind the original hole (so the new hole just touched the original hole), then filed away the metal between them to form a slot. IIRC I had to bend the lip of the crossmember a bit as well, to clear the new mount position; but that may not be necessary.

I've never tried a 28% OD, but my feeling is that it might be a bit much for a stock TR motor with the stock 3.7 rear end. Taller gears mean lower rpm, but they also mean less power available (without shifting out of OD). And it's nice to have something on tap for climbing hills, changing lanes, etc. without shifting gears.

To rework Randy's table a bit (bhp numbers are from the TR2 curve in the workshop manual, but TR3 numbers should be similar at these speeds)

75 mph = 3750 rpm 1:1 80 bhp available
75 mph = 3074 rpm 1:1.22 68 bhp available
75 mph = 2930 rpm 1:1.28 64 bhp available

Also, the 22% gives an almost-perfect split between 2nd & 3rd gear; while 28% is going to move 2nd OD up much closer to 3rd direct.

Assuming the unit hasn't been tampered with, the brass tag on the OD will have the ratio marked on it in front of the model number. Eg, model 22/1374 is a 22% unit. Of course the gears can be replaced (as a set) to change the ratio, but I don't think that is very common.

 

[TFB]

Thanks Guys.I did check quantums web site and sent a note to Wishboneclassics for pricing on later model full sychro or converting mine. Thier site also mentioned a thicker thrust washer they use.
thanks again for all the great info.
Tom

 

[HerronScott]

Yes, the front cover was slightly longer with the earlier clutch. But lots of folks have reported that the shorter cover works OK with the early clutch. The TR6 input shaft is also somewhat shorter, so it doesn't engage as far into the pilot bearing. Doesn't seem to be a problem.

Thanks Randall! I haven't done anything with the TR3 yet so wasn't sure if that was an issue or not.

Scott

 

[TFB]

I am going to have the ebayer referenced in starting post ,TR-man Brad, build me an overdrive,TR3B with top oil fill and dipstick.Accumulator is sleeved to the size of later tr6 type,which he states will give softer engagement,and easier future service.
Any other things I may want to consider or be aware of?
Thanks again
Tom

 

[Moseso]

Sounds good to me. I, too, have had good experience with Brad. He seems to know what he's doing, and handles any "issues" that may arise in a way that keeps customers happy.

 

[71tr]

While on the subject of overdrives, anyone care to comment/compare the "A" type vs "J" type of overdrive for function, reliability, etc.?

 

[TR3driver]

While on the subject of overdrives, anyone care to comment/compare the "A" type vs "J" type of overdrive for function, reliability, etc.?

The J-type is more rugged, easier to service and likely better for long-term reliability. They looked for all the shortcomings of the A (and D) types, and eliminated them with the J-type. If all you are looking for is reduced rpm while cruising, then the J would be my choice.

But the A-type gives those instant shifts even in 2nd gear; which to me makes it both more useful and much more 'sporty'. I'm definitely glad I've got an A-type in my TR3, wouldn't want it any other way.

And I'm still hoping I can talk a friend into selling me a Stag A-type to replace the J-type I installed.

But note that installing a J-type in an early TR6 is rather more work than the A-type. You'll have to redesign the rear motor mount, and likely cut off the frame tabs for the old rear crossmember. Your speedo calibration will be wrong, too.