TR4/4A OD Addition to a Non Over-Drive Transmission - my attempt

[Zitch]

So I don't have enough things to do so I though I'd try to Add Overdrive to a Non OD Transmission.

This is what I'm starting with......

Step one:

Read all I can on the topic.....

Find and old 4 speed out of a Tr4 or Tr6

Found it....$100 on Craigslist

Insides look OK, everthing seems to mesh well.

Step 2:

Find all you need to convert this one to Overdrive.....

- Short main shaft

- Overdrive

- Flange

- adapter plate

- Other stuff....

Working on it......

 

[TRopic6]

Looks like a nice tranny Zitch. It's got that funky tail-shaft counter weight they put on some TR4 & 4As.

Jeff

 

[Marvin Gruber]

Ted,
have you ever taken a TR trans apart? Well its not the taking apart thats hard, its putting it all back together thats a pain. Its going to a hard to just find the o/d unit. Best bet is buying the whole trans. Be careful on what you buy, there are several things that get you in trouble. I leave the o/d rebuilds to someone else.
Marv

 

[TR3driver]

Interesting. I hadn't realized that the "counter weight" was used on non-OD trannys as well. If it still has the rubber bushing inside, I'd like to see a photo of that.

Be sure to check out the countershaft carefully. I see what appears to be a few metal flakes in your photo and I'll bet that's where they came from.

 

[CJD]

Also plan to replace the synchros. The 3rd gear synch looks a bit close and the dog teeth a bit rounded...probably worn out. Could just be the photo, though.

 

[Geo Hahn]

Interesting. I hadn't realized that the "counter weight" was used on non-OD trannys as well...

The non-OD box on my 64 TR4 had that lovely weight hanging on it. I transferred it to the OD gearbox I put in.

 

[Marvin Gruber]

Randall,
never seen weight on an overdrive trans, I have a box full of those weights.
Marv

 

[TR3driver]

I don't have a photo, but long ago and far away I bought a TR4 for parts (including the OD) and it had the weight. (Mostly the same OD I have in my TR3 today IIRC.) Possible it was put there by a previous mechanic, I dunno for sure.

The 4A SPC lists two different part numbers for the weight, one for OD and one for non-OD. The "overdrive condition" P/N is 132604, same as the P/N listed in the TR4 SPC (without specifying OD or non-OD). But the TR4 SPC lists for a fairly small range of cars, less than 20,000.

The weight I got, though, was way loose on the center bolt. I assume there was supposed to be a rubber bushing in the middle (the SPC calls it "weight and bush assembly") but I've not seen one with the bush intact.

 

[glemon]

It is quite a job to do the O/D conversion on a non O/D in my TR250, it worked for about a year, but was intermittently hard to get into 2nd, eventually not going at all. I tried again, it still wouldn't go into 2nd. So I guess I am 0 for 2 on tranny work (I know what I did wrong the 2nd time, the first time is still a mystery).

I have rebuilt several motors with no issues, trannies are harder (in my opinion). Half of what a shop will charge you is pulling the gearbox, so if that is already done....

I had a local shop do mine, no special TR expertise, it is still going fine after about 5 years now. The O/D I bought rebuilt, I haven't ever tried to do one of those, lots of information out there about rebuilding those though, as well as tranny rebuilds, you are on the right track reading as much as you can, I have read about others saying they tore them apart, put the new synchros in or whatever and buttoned them back up no big deal, so maybe I am just a ham fisted hack and it will all work fine.

 

[JerryVV]

When buying an OD unit be certain it was from a TR and it's an A Type Unit. There are different units from Healy's and Volvo's that might be problematic on the rear mount. Also with regard to the Transmission pictured and "metal flakes" mentioned. I agree the flakes could be from the countershaft bearings so a good inspection there is in order. A fellow by the name of Steve Yott modifies the countershaft to take 2 rear bearings. A wise choice as long as you are in there. Don't rely on a visual inspection of the syncro cups; measure the clearance and if within specs stay with the OE cups and reuse them. There are repros available that are suspect. If you get as far as rebuilding the pictured trans and an OD unit, mating them together is a pain. You must align the splines in the roller clutch deep inside the OD unit while compressing the 8 springs and making certain the pump cam is positioned correctly such that the units assemble easily. Do not try to draw them together with the long studs until you are certain everything is aligned or you will bend and break important parts. Other than all of the above have a go at it. An OD is a great improvement to a TR.

 

[CJD]

Every time I read this post I cringe a bit. Here is my thread when I rebuilt an OD a couple years ago. There are at least a half dozen spacer washers that must be custom fit. I was glad that, having been installed in the same OD, mine all were within clearance. I would have cried if I had to disassemble the OD several times to get the correct clearances by trial and error. This will be a very challenging project...

https://www.britishcarforum.com/bcf/showthread.php?100040-Here-We-Go!/page2

Here is a thread that gives a bit of insight in rebuilding the tranny...which is a snap compared to rebuilding the OD.

https://www.britishcarforum.com/bcf/showthread.php?100241-TR2-3-Gearbox-Rebuild

 

[TR3driver]

Every time I read this post I cringe a bit. Here is my thread when I rebuilt an OD a couple years ago. There are at least a half dozen spacer washers that must be custom fit. I was glad that, having been installed in the same OD, mine all were within clearance. I would have cried if I had to disassemble the OD several times to get the correct clearances by trial and error. This will be a very challenging project...

https://www.britishcarforum.com/bcf/showthread.php?100040-Here-We-Go!/page2

I'm not sure whether to put this in that thread (which I hadn't seen before) or this one. Guess I'll put it here.
A question was asked about the importance of lining up the dots on the planetary gears. The problem is that each of the 3 planetary gears has two sets of gear teeth, and they don't have the same number of teeth. So, there is a phasing type relationship between the inner teeth and the outer teeth. There is only one place around the gear where the two sets of teeth line up with each other.
But, the way it goes together, all 3 sets of outer teeth are locked together (by the sun gear), and all 3 sets of inner teeth are locked together (by the annulus). So, all 3 gears need to be in the same phase relationship to each other. If not, the gears either won't mesh smoothly (one gear tries to carry all the load, which makes the sun gear try to run in a circle relative to the annulus), or it just won't go together at all.

I couldn't find a good diagram, but imagine if you will, two of the 3 planetary gears installed in the annulus and engaged with the sun gear. We'll pretend that only half of the carrier is in place, so we can try to slide the 3rd planetary gear into place without disturbing the other gears. But the two sets of teeth on the planetary gear can only line up with both the sun & annulus gears in one particular orientation. If you try to turn it by one tooth on the outer teeth, then the inner teeth won't be lined up, etc.

So the dots are a shorthand way of getting all 3 gears turned so they line up at the same time.

John mentioned the Buckeye articles, which can be found at https://www.buckeyetriumphs.org/technical/AOD/AOD1/AOD1.htm

There are another couple of good articles on the VTR web site
https://vintagetriumphregister.org/maintain/TransRebuild/OverDriveA01.pdf
https://vintagetriumphregister.org/maintain/TransRebuild/OverDriveA02.pdf

And FWIW you can read (or download) the factory OD manual from https://drive.google.com/open?id=0B2H2NJt34OffODZjM2FkY2ItZTBlZS00N2Q3LWJmZTUtMTRkN2MxNDI4M2Vj

There is also some good info in the various workshop manuals
https://drive.google.com/open?id=0B2H2NJt34OffYWZiN2VlZGMtNTkxMi00NGUzLWE4NzMtMGRkODRkYzU3MDU1
https://drive.google.com/open?id=0B2H2NJt34OffN2FkZjI2NjktNWJiMy00YWExLWIyNjctOTYzNmI3OTg2ODM0
https://drive.google.com/open?id=0B2H2NJt34OffZTJaeXJhWllGWnc


It's a bit Rube Goldberg-ish (especially the operating valve and solenoid), but I wouldn't rate it any harder than doing an engine or transmission for the first time. Just different.