Manual Transmission Theory

[meadowbrook]

I have a transmission question concerning my R7 Overdrive, but it should apply to any manual trans.

 

As I understand it, my 1950 fluid drive equipped Meadowbrook can actually be left in 2nd gear and be driven like that all day with no clutch actuation, if one is not in a hurry and will not drive much over 30 MPH.

 

However I cannot do that because if I undergo too many torque reversals (accelerating and coasting) in 2nd, it seems like it progressively disengages until it simply pops out of 2nd. This will not happen in 1st or 3rd. Also, If I just maintain speed in 2nd, it does not pop out of gear.

 

But, if I place the trans in Overdrive mode, this does not happen because in OD mode, the vehicle freewheels, so the trans only sees torque when accelerating.

 

So this confirms that the torque reversals are what seem to be nudging the trans out of 2nd gear.

 

I have looked at the linkage to see if it is fully engaging the gear and it is, and on Asche's advice, I shimmed the gear detent springs to make it a bit harder to pop out of gear, with no effect.

 

What do you guys think might be the issue? Are there components in the gear stacks that may be worn? Or could it be worn bearings that support the gear stacks?

 

Anything else I can try before I pull the trans and dismantle it?

 

Aside from this, the trans shifts nicely (aside from an occasional grind if I shift from 1st to 2nd too fast when it is cold), is not noisy and basically performs flawlessly.

 

Thanks

 

Joao

[Lloyd]

I had a similar problem with a 4 speed on a 63 Grand Prix, was in second gear as well.

Adjusting the shift linkage helped a lot, after adjusting it quit jumping out of gear everytime I took my foot off the gas but I still had to hold it in second and accelerate to get it to stay in second.

Dismantle showed a worn synchronizer on the second gear.

[Daliant.]

 

Aside from this, the trans shifts nicely (aside from an occasional grind if I shift from 1st to 2nd too fast when it is cold), is not noisy and basically performs flawlessly.

 

 

 

 

 

 

 

I'd say either the engagement teeth on the 2nd speed gear are worn or the syncronizer is sloppy, plan on cracking the tranny open

Edited July 16, 2014 by Daliant.

[Lumpy]

Yes the synchros usually being the main cause, and bent shifter forks will do that, and all those parts getting sloppy and worn adds to the mix.

Every time you allow it to pop out of gear, it will get a little bit worse/damaged. When they start popping out with a BANG, it won't be long until it will no longer stay in gear, even if you try to hold it in. At all. So, be sure to hold it in gear...every time it pops out, more damage will happen.

I'm not sure why this takes place usually in second gear, but that seems to be where it happens. Again, every time it pops out, you are about another two or three weeks closer to a tranny rebuild. Don't let it pop out.

Anyway you look at it, your tranny is going to need some attention.

ken.

[meadowbrook]

Thanks for the tips. It has been doing this for a couple if years and so I don't allow it to pop out by simply not coasting in second for very long. No banging, though, when it pops out it feels like I pressed the clutch. I just realize ut because when I accelerate the engine the revs with no vehicle acceleration, the I notice the shift lever is lower than before.

[nonstop]

Another possible cause is the preload on the bearings. I have not been in one of these trannies, but worked on a lot of trannies (automotive instead of the human kind) when I worked in a trans shop. If there is too much play in The main or counter shaft, it can cause it to pop out of gear. You probably will not be able to get an answer without taking off the shift cover.