a type overdrive transmission

[vrod]

I,m thinking about taking my overdrive transmission apart just to check things out. The last time my tr was on the road, it would slip out of overdrive upon hard exceleration. one of the things I might try before the tear down, is to empty the transmission oil and put some atf in and run it for a week or two then empty it, and see what it does. (thanks larry4A for that tip). However if I take the transmission apart does anyone have any good suggesions for the type of gasket sealer to use upon reassembly. The best I can come up with is (The Right Stuff) which I can get at the local Auto Zone. I know these are high oil preasure transmissions and may never be cured of oil leaks, but the dog ends up walking over my triumph oil leaks and this seems to upset the wife, any help here would be much appreciated

 

[piman]

Hello Vrod,
the overdrive unit is not a 'leaky' item and doesn't need any special care in assembly from that point of view.
I'm wondering why you want to use a much thinner oil than the specified EP90 oil recommended for this unit? By the way, you may not be aware that the use of anti friction additives is strongly detrimental to the working of the overdrive.

I would suggest a normal oil change, and when drained remove the overdrive sump plug and clean the filter and magnetic rings inside it. It's also worth checking the engagement, by putting a 3\16" pin in the little lever on the opposite side to the solenoid when it is energised.

Aplologies if I'm teaching you to suck eggs.

Alec

 

[MDCanaday]

Vrod, the slipping out and in on the A type could be electrical, but "hard exceleration" makes me think worn clutches.You might do well to go through the the laycock book and then tear it down. Short term, a flush and fill might improve things, but not for long.
MD(mad dog)

 

[vrod]

thanks for your response, I was thinking it was a worn overdrive clutch or pump. There seems to be many sugestions as to the type of oil to use. I have read 30 wt non detergent in the repair manual but am wondering how a heavier oil would make it perform, I thought about using the atf only for flushing purposes but inevitably it just needs torn down, thanks again

 

[piman]

Hello Vrod,
I don't know what manual you looked at, but my Triumph workshop manual states that the oil should be EP90, the same oil as the differential.

If you have a manual to refer to there are a couple of things you can check. Firstly is the hydraulic pressure you have. If the pressure is below spec it's possible the pressure relief valve wants re-seating. As I said earlier, check that the solenoid is engaging correctly via the check hole in the lever. It may save you having to strip the gearbox down. If you have never fitted one of these back onto the main gearbox, be very careful to line up the two sets of splines. If it goes tight when you are screwing up the jacking screws don't tighten any more or you can easily crack the O\D front plate (I know, I've done it.). Sometimes a tap with a heavy soft hammer will engage them, but if not take it off and realign the splines.

Alec

 

[Dave Russell]

[ QUOTE ]
Hello Vrod,
It's also worth checking the engagement, by putting a 3\16" pin in the little lever on the opposite side to the solenoid when it is energised.
Alec

[/ QUOTE ]
Hi guys,
Using the gage pin in the lever is not a very reliable or accurate method of setting the control valve on a type A overdrive. Especially if the parts are a bit worn. Wear in the levers & internal lift arm, usually results in not enough lift. Too much lift may not let the ball seat & not enough lift will not let the OD operate reliably. Also make sure that the ball is not damaged & is seating well.

Much better to measure the actual ball lift with a dial indicator & set the adjustment to .040" to .045". It takes a little fussing with the indicator, such as fabricating a shouldered spacer to hold the indictor at a fixed, centered height in the hole, & a cup shaped indicator tip to center it on the ball. Still worth the effort as this setting is pretty critical.

Always check the tiny relief hole in the side of the valve plunger body (located under the ball) to make sure that it is not clogged. Some increase in shifting speed can be obtained by enlarging this hole from .032" to .047".

On the other side of the OD box, solenoid side, more reliable operation can be obtained by increasing the pump check valve plunger length from .120" to .220". A .125" spacer under the accumulator springs will also help give more reliable & positive OD operation.

I don't think that the type of lube is too critical. Triumph suggests gear oil, Healey suggests motor oil. They are about the same viscosity since motor oil & gear oil viscosities are measuread on two different rating systems. The only caveat is to not use oils which contain sulphur or anti friction additives. I personally like Red Line MT-90 or MTL. It has a lower friction coefficient & lets the synchronizers & OD engage more positively.
D

 

[piman]

Hello Dave,

where did that dimension of 0.040" to 0.045" come from? I'm interested as I have not seen any reference to it in any manuals.

Thanks,

Alec

 

[Alan_Myers]

Hi all,

I've been doing a lot of A-type research, because I.m adding one to my car and want to know as much as possible about it.

I've often heard Castrol or Valvoline 20W50 Racing oil (non-detergent) is good to use in the A and J-type overdrives.

Also with a slipping OD, wouldn't it be worthwhile to clean the filters? There is the one on the bottom, under the big brass plug. There's another inside, but I'm not 100% sure the best way to get at it.

Intermittent operation might also point to the pump failing to provide adequate pressure, a pressure test could confirm if it's okay or not.

Also, I've recently seen some mention that modern replacement clutches are a big improvement, stronger and even more reliable than the originals, which weren't bad.

Cheers!

Alan

 

[Dave Russell]

[ QUOTE ]
Hello Dave,

where did that dimension of 0.040" to 0.045" come from? I'm interested as I have not seen any reference to it in any manuals.
Thanks,
Alec

[/ QUOTE ]
Hi Alec,
MY A/H shop manual (Sept. 1956) says 1/32 inch, others say 1/32" to 1/16". The type A overdrive used in A/H & early Triumphs Is basically the same unit. The J OD type may be entirely different with different settings.

Too little lift gives unreliable shifting & or slower shifting. Higher lift, up to a point, gives faster shifting. If there is too much lift the ball may not seat when the solenoid is released. The usual problem is that the setting gage arm Is not very precisely placed & wear in the components can make the actual setting vary considerably from the intended lift setting. I prefer a little more than 1/32" lift to compensate for temperature variations of dimensions & oil viscosity changes. AT 1/32" lift the shifting was not always reliable under all conditions. At 1/16", it sometimes didn't work at all. In any event, 1/32" to 1/16" is impossible to accurately measure by eye. Your experience may vary.
D