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TR2/3/3A the overdrive units

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sp53

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Well I have been reading about the overdrive units and was thinking I should put the over drive transmission in and separate the OD from the trans like described in this article for Healey’s.

https://www.team.net/www/healey/tech/big_hly/od/delborder_od.html#part1

I still have so many questions, but from what I am reading I should rebuild the OD before I try it. Does that sound correct? I think Geo was kindly suggesting that, but my inpatients and fear of breaking something that is not broke yet was winning out.
 
Without going back and finding previous threads I do not recall the history of this unit. That and the condition you see may suggest what to do -- but there are some things that can be done proactively that are far short of a 'rebuild'.

If I made the case for bench testing it was just because of the effort of R&Ring the gearbox w/ OD in a finished car. Not technically difficult but possibly physically demanding depending on whether you're working solo and how you feel about wrestling a weighty unit in close quarters.
 
So, did you decide to go ahead and rebuild...or were you going to install and test first?
 
If the oil is reasonably clean, pressure looks OK, and it works in a bench test; then I'd say go ahead and run it.

BTW, you need to be aware that not all overdrives are created equal, not even all A-types. For example, the modification described in the above article under "OD competition secrets of the 60's" applies to only a relatively small number of TR units. All "solid axle" TR units already have the larger accumulator, and later IRS TR units are made such that they will quickly fail if you try to install the larger accumulator. They have a single large hole for the relief instead of a series of small holes. Only the early IRS units have the housing that can take the large accumulator, but were fitted with a small accumulator by the factory.

In my opinion there are several other inaccuracies in that old article by Del Border, at least with regards to Triumphs. Of course a Healey is not the same as a TR, and Del was writing about a Healey OD & transmission, so that may be the reason. While I don't say it is impossible to reinstall the OD with the transmission still in the car, it is going to be dang difficult. It's hard enough even with the transmission out! You have to get 3 different splines perfectly aligned, one of which you can only control by tipping the unit up so gravity engages either the OD or direct drive clutch. And the sprag clutch (aka unidirectional clutch) rarely fails unless someone has forced the car backwards with the OD engaged; and then it generally fails in an obvious fashion. It doesn't just wear out. It is also not, as Del implies, solely responsible for carrying the load in direct drive. The direct drive clutch is supposed to carry the load, the sprag clutch only covers the gap while the clutch is moving between OD & direct. Without the direct drive clutch, reverse wouldn't work at all.
 
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I am still on the fence of a total rebuild, and I am leaning toward running it after hearing the feedback. The fluid looked clean, but I am still not sure how I would test for pressure. The bench test with a drill motor and coupling would not be a problem, but again I am sure what I am looking for. My problem is I have no experience with this stuff, so it is more like a baptism by fire. The most fundamental tips would be appreciated. Should I purchase a pressure gauge and if so what calibration would I look for?
 
You'll need both a gauge and the special adapter to connect it to the OD. Here's one source https://www.geocities.ws/jholekamp/
Of course, if you are stubborn enough, you can make your own adapter. I enjoyed doing it as a lathe project (learning to be an amateur machinist and it's a lot more fun to make things that are useful).

Here's a good article that covers bench testing an A-type
https://www.buckeyetriumphs.org/technical/AOD/AOD4/AOD4.htm
There's also some coverage here:
https://vintagetriumphregister.org/maintain/TransRebuild/OverDriveA02.pdf

But basically, you will be checking that the unit will build and hold pressure, while engaging and disengaging overdrive.
 
SP53-I don't know where you are located in WA, but there are many people in the TYEE club in the Seattle area or PTOA club in Portland that would probably loan you the pressure gauge and help you evaluate the tran./OD before you install it.
Randall-Interesting comment about the differences between the large&small accumulator ODs. I have a large accumulator OD from a TR3 in my 6. At some point, I figure the bore in the accumulator will have worn enough to require using the sleeve&piston from the small acc. My early OD has a removable core plug for the relief passages in the acc. and is probably a source of leaks. I noticed that the later small acc. ODs don't have this plug. Probably because the pressure relief was provided by the holes in the sleeve.
I agree that replacing the OD with the trans in the car would be difficult or impossible. Keeping the clutch return springs in place would be very challenging.
Berry
 
I have read that the early A types (mine is May 1954) which operate only as a 5th gear can be modified to operate on each gear. Is that hard to do? Does is require a different switch on the dash than my existing push-pull? And does it risk damage or reduce reliability? Any thoughts appreciated.

Dan
 
Dan-From the info I have read, when the ods were modified to function in 2nd gear, the operating pistons were increased from 1-1/8" dia. to 1-3/8" dia. and the change took place at TS5979. The brass tag on the OD prior to the change would be 22/1275. After the change would be 22/1374.
Berry
 
To expand a bit on that, the conversion is not terribly difficult and you can keep your original push-pull switch. However, it does require either a different overdrive, or at least a new center housing. It _might_ be possible to modify your existing housing for the larger pistons, but I doubt it.

Another possibility would be to go ahead and do the conversion with your existing unit, and then refrain from doing those full throttle shifts in 2nd gear. Just use the clutch every time and it will probably work OK even with the smaller pistons.
 
titanic said:
At some point, I figure the bore in the accumulator will have worn enough to require using the sleeve&piston from the small acc.
Click to expand...
That's a common repair trick. Much easier than boring the housing to take a thin sleeve so you can continue using the large piston.
My early OD has a removable core plug for the relief passages in the acc. and is probably a source of leaks. I noticed that the later small acc. ODs don't have this plug. Probably because the pressure relief was provided by the holes in the sleeve.
Click to expand...
I'd have to look to be certain, but I seem to recall that the core plug is from where they drilled the row of small holes.
 
Randall that last article was a huge help, thank you. The trans has 63K ---TS# and a serial number 22/1374/ 011174 Laycock Normanville, so I guess it is a common A type? Anyways, you know that bolt that holds down the pressure spring/ball where I am going to hook up the pressure gauge, is that small bolt supposed to be super tight. I have a 6 point 7/16 wrench on it with a good fit (I heard they were BW?) and I am getting nervous about it breaking, anyway I almost thought it could be reverse threads?, but could not see why. Is just tight, I guess?
 
Yup, just tight. Right hand threads, 7/16 is the right size (not Whitworth) and 6 point should certainly help. You certainly would not be the first to round it off!

Those numbers indicate a standard TR3 through early TR4 A-type with (at least originally) cast-iron rings on the (large) operating pistons and the large accumulator. The leading 22 indicates the overdrive ratio is 0.82, while the central 1374 is the model number and the last 6 digits are a serial number.

Somehow, I thought the switch to the "notched" drain plug was earlier, but the parts catalog says I'm mistaken. Does yours have the notches, or a hex head? The home-made tools I showed earlier are for the later plug (which is what I have on my TR3, but it's a hodge-podge of parts from multiple cars).
 
Well got the bolt out and I assume it is alright that the lever dropped down and lose with the bolt, ball, and spring out. The trans does have the brass plug with the notches. I actually took one of your ideas Randall in using the angle iron with two holes to hold the differential flange for tightening and the cut a notch in that tool and slide that between the notches on the brass plug and it came lose with some effort.

This trans looks unmolested and I might have gotten lucky. Some of my detective work suggests the OD did not work for some time because of the solenoid being in two pieces and the clutch fork pin was sheared and looking at first gear slider, they had a hard time getting into first gear when they did drive it. Moreover, the story from the junkyard where I got the parts maintained the car sat in the garage for twenty plus years. Hopefully that is because the engine would not turn over as the junk yard suggested when they got the car after the fire. The bolts all around the trany look unmolested, but there is a jam nut on one stud that holds the beefier tail shaft on for some reason. The brass shifting forks hardly show any wear; whereas I have seen them in the past where they are cut into maybe a 1/16 or more with wear. Time will tell.
 
You found the parts in a junk yard...that's amazing! Be sure to keep us posted, as I will be where you are in a couple months.



If you look closely, you can see that mine is so stuck in some unknown gear that someone bent the shift lever trying to get it into neutral. Can't wait to see what that's all about!?!
 
Yeh the car was in a Yank a Part junkyard out on the Olympic Peninsula. They advertised the car on Craigslist, but adjusted the prices. I got the od for 500.00 and I suppose the parts are worth that. The guy gave me the seats out of it because they were burned and a little bent plus very rusty. The seats took me back to an old memory of those old seats I sent you. Those seats were rusty and ugly and I was younger and I took them into a sand blaster guy with an old frame and when I went to pick the stuff up he had shoot the whole batch with this black coarse sand. I though wow that is too much for those seats, so I put them away out of disgust. Anyways it is that old story, “one has to pay for that education somehow.”
 
sp53 said:
looking at first gear slider, they had a hard time getting into first gear when they did drive it.
Click to expand...
Damage there is very common on the early "crash" boxes. Most people don't know how to drive them and keep just grinding it into gear. The secret is to pull the lever back towards 2nd gear, just enough so the 2nd gear synchros stop the shaft from spinning (with the car stopped), before shifting into first. And of course you have to either unlearn doing "California" stops, or do it in 2nd gear.

It does sound very encouraging; although I'm not seeing the break in the solenoid that you described. The plunger normally falls out like that, there is nothing to keep it inside once the solenoid is removed from the mounting plate on the OD.

Oh yeah, make sure the stop that limits how low the solenoid plunger can fall is present and accounted for. I forget offhand which are which, but some units had a rubber bumper there that is frequently MIA. And if the plunger falls too far down, the solenoid may not be able to pick it up; which can lead to the solenoid burning up. I added a fuse to mine, so the fuse would blow instead of burning up the solenoid if something keeps the plunger from going home.
 
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Ok-- Randall that is the 2 piece deal I was talking about, so perhaps the solenoids is good. Yes absolutely there is only a bare remnant of the rubber stopper. I see in the one article they suggest tapping the hole and putting a jam nut there. I am not keen on tapping that little protruding piece. What did you do? It looks like I could put a small machine screw in there with a neoprene Fawcett washer or rubber or something.

What about after I pulled out the ball/spring valve, and the arm drop down away from 3/16 hole? At first I thought I broke something because I was still cleaning the case when I noticed the lever was down. I have also taken off the pinch bolt and arm and just have the numb sticking out on that side. Could that be a problem? I just have no experience right now with this stuff and I do not what to pay too much for this education, I am getting old.

Anyways I see in Moss that they offer rings for the accumulator and I think that is what Geo was talking about as a partial rebuild. Is that correct? At any rate, these parts look expensive, so I hope the pressure pumps up and I can avoid some cost. There is a guy in town that works on welding gauges and such I will go down and see if he has something before I purchase the one on line.
 
You will need an adapter to fit in the operating valve plug hole. They are not commerically available, but easily made by someone with a lathe. Or buy the gauge with the adapter for about $50. A minor rebuild is usually gaskets, o rings, and seals(not accumulator rings), if you are lucky. Otherwise the parts add up quickly.
Berry
 
I'm afraid I've forgotten the details, but here's a photo

As I recall, the hole was too large to tap, so I just stuck that SHCS in there and made the adjustment with the flat washer(s). Seems like I had to file the bottom flat for the nut.

The arm falling down is normal. It's just a rod that runs all the way through the housing, with a small cam that lifts the valve spindle. With the plug and spring, etc removed, the spindle moves up very easily. The only thing to watch out for is that the cam may turn far enough to let the spindle fall down again, which will block turning the rod back to where it belongs. If that happens, bend a paper clip to fit into the hole of the spindle so you can lift it back up and turn the cam where it belongs.

I must've missed the comment about a partial rebuild, so not sure what Geo was talking about. He'll be along in a bit, so maybe he can amplify. But I wouldn't expect the accumulator rings to be a problem, unless perhaps one got broken during installation. Which is a good thing, since I believe you are mis-reading the Moss web site. They only list rings for the later small accumulator setup. If you need early rings, though, they are available from ORS in the UK.
https://www.overdrive-repairs.co.uk/buy_spares.php?cat=A Type Spare Parts List

Oh yeah, as Berry said, the adapter is important. You can't just jam some pipe fitting in there, because the adapter has to mimic the function of the plug to make the valve work. (Not to mention the damage likely from trying to use the wrong fitting. Those aren't pipe threads.) I gave the link to Jay Holekamp's site before, or you can order that from ORS as well (Jay's is cheaper, though).
 
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