TR2/3/3A Question on A type overdrive spec for "clutch movement from direct to overdrive"

[TuffTR250]

Question on A type overdrive spec for "clutch movement from direct to overdrive"

I put my A-type overdrive together and was following the Greasy Hands article on measuring the movement of the sliding member by pulling the bridge pieces in and out. My TR4 Service manual for the overdrive says under the Misc. Dimensions and Tolerances section that the "clutch movement from direct to overdrive" should be 0.080" to 0.120" allowance of for 1/8" wear of direct drive clutch.

However when I measured mine the sliding member movement is only .060". It is going into overdrive because I cannot turn the shaft counterclock wise and also the flange turns one full turn while the shaft turns about 3/4 the way around. Is this short movement a problem, and if yes, how do I correct it? Thanks!
Regards, Bob

 

[TR3driver]

Re: Question on A type overdrive spec for "clutch movement from direct to overdrive"

As long as it turns freely (no drag from the opposite clutch) in both OD & direct, I don't think it will be a problem.

On mine, there was no movement at all and the shaft locked solid. I mounted the clutch plate in the lathe and took several light cuts off the direct drive face to get some clearance. (On the theory that the direct drive side sees very little wear, so it's best to leave the thicker material on the OD side.)

 

[TuffTR250]

Re: Question on A type overdrive spec for "clutch movement from direct to overdrive"

Thanks Randall! I was wondering (and hoping) if there might be more movement in the sliding clutch once it is all together and the pistons under pressure are forcing the sliding member forward? When I looked into the overdrive it did not look like the material of the clutch was really very tight against the brake ring when I pulled the bridge pieces outward by hand.
Regards, Bob

 

[TuffTR250]

Re: Question on A type overdrive spec for "clutch movement from direct to overdrive"

Seems like my small clutch clearance is causing a problem, so I'd appreciate some advice.

I tested the overdrive using the "air injection" method described in the part 3 of the Buckeye article, with springs installed. When I first turned on the air I heard the OD clunk into overdrive. But it would not go out of OD using the operating lever, and I heard a lot of air escaping. I shut off the air, and decided to squirt some 85/90 GL4 gear oil into the operating valve and also a bunch of oil around the accumulator piston. I again applied air at 100 pounds pressure. This time I did not hear a clunk but there was no longer any escaping air noise. The clutch sliding member and thrust ring were forward in overdrive position. I then took the air pressure off. However, when I tried to move the sliding member back out of OD mode using the bridge pieces, it would not move at all. Eventually, not sure why, I was able to get it out of OD mode and able to move the sliding member in an out. The problem is that now the clutch movement from direct to overdrive is now only between .045 and .050 inch. Even with that measurement, when in overdrive mode the flange turns one full turn while the shaft turns about 3/4 turn (as it should). The problem is that I can now turn the shaft counterclockwise when it is in OD mode, although to turn it takes a bit of effort but it is not firmly locked out of the counterclockwise motion.

Randlall, per your previous response, it appears that I do have the same problem you mentioned above. I am a bit confused on why I can turn the shaft counterclockwise when it seems to be in OD mode per the turn ratio. Is the counterclockwise turning problem a direct result of not enough clutch clearance? Also, since I don't have a lath, is there any other method of increasing the clutch clearance other than making the clutch lining thinner? If the only method is thinning down the clutch lining material, can I use sand paper to take some clutch material off?
Regards, Bob

 

[CJD]

Re: Question on A type overdrive spec for "clutch movement from direct to overdrive"

It sounds like the actuating lever may need to be adjusted...as it's not relieving the pressure. I found on mine that because of the age and years in use, there is more slop as the actuating rod passes through the OD than there was when it was new, so the factory setting would not allow my OD to release. I had to tighten the clearance on the right side of the box to allow the valve to release. Just putting a pin in the lever and setting the left side didn['t work. I kept gradually increasing the throw until I got to a setting that gave me consistent actuation and release.

The fact that it doesn't lock from opposite direction rotation may not be a big deal. The one way clutch rollers may not have seated completely with the fresh rebuild. If you put enough torque on the clutch, I assure you it would lock solid. By hand you just don't apply that much torque...and good that you can't!

 

[TR3driver]

Re: Question on A type overdrive spec for "clutch movement from direct to overdrive"

My guess would be that the 100 psi isn't quite enough to fully lock the OD clutch against the force of the direct drive springs. That might also explain the reduction in movement. Is there any way you can get a bit more pressure?

 

[CJD]

Re: Question on A type overdrive spec for "clutch movement from direct to overdrive"

You can always try this:



Air is close, but not always exactly like using oil.

 

[TuffTR250]

Re: Question on A type overdrive spec for "clutch movement from direct to overdrive"

Thanks John! Before I reinstall the transmission and the "new" overdrive I plan to test it with an electric motor bolted to a pulley on the back flange. But since I do have a good size drill I will try your drill method first. However, I don't want to take the transmission out of the TR3 yet since my son and I want to drive it as much as we can this summer. So that better test will have to wait a while. I'm just trying to test as much as I can without the transmission so when I get ready for merging the two, I can be fairly sure the overdrive will work. Thanks for your help and responses to my questions. It is a great help!!

Randall, I took your advice and increased the air pressure. My compressor says it will go to 150 pounds but I couldn't get my meter to go higher than 120 pounds. I guess it is not a real good meter. But 120 pounds seemed to be a lot better than 100. In addition, since I have brand new thrust springs, I remembered that the Buckeye article said to back off the plywood some in the overdrive is not shifting. So I left the plywood back away from the front of the overdrive a little more than 1/4 inch. I also put more oil around the accumulator piston and in the operating valve hole before I installed the "air injector". I made sure the lever was in the non-overdrive position, and then turned on the air. The overdrive reacted correctly and did not shift until I pushed the lever down to activate it into overdrive. It clunked nicely into overdrive and then when I pulled the lever back it went out of overdrive mode. I did that a couple of times and it worked correctly each time. In overdrive mode the back flange was turning one full turn while the shaft turned approximately 3/4 turn, and I could not turn the mainshaft counterlockwise at all even with as much force as I could put with just my hands. I could not tell how much clutch movement I was getting when the air pressure was applied but it seemed to be quite a bit more than when I move the bridge pieces by hand. So I've come to the conclusion that although I don't have the clutch movement by hand as suggested by the TR4 shop manual, the overdrive seems to be working correctly and shifting as it should under pressure. So I believe I'm ready for the next step of merging it with the transmission, but that will have to wait until the summer driving weather is over.
Thank you very much for the help and advice!!

Regards,
Bob