G50 Third Gear Frustration

1990C4S · 06-17-2011, 12:20 PM

I just rebuilt my G50 (160,000 miles or so).

My issue, and the reason for the rebuild, was shifting into third; the synchro did not work.

So on tear down I found some wear on the third gear synchro. I replaced the third and fourth gear synchros and re-assembled.

Absolutely no change. I can not get into third gear when moving. I can start off in third, but I can't 'double clutch' and get into third, it simply feels like two gears that won't mesh.

My guess (now) is that somehow the bearing on the loose third gear has too much drag, and is preventing the synchro from doing it's job, i.e. matching rpm's.

I spun the gears on assembly and did not feel any extra drag on third. But I am totally stumped now. And I would like to know what to look before I tear it down again.

Thoughts? Ideas?

Peter Zimmermann · 06-17-2011, 01:19 PM

1. What was your measured gap of the original 3rd gear synchro when it was pushed onto its cone?

2. What was the same measurement for the new synchro?

3. You don't mention a new guide sleeve and operating sleeve?

4. Are you sure that your intercept stops are installed correctly?

1990C4S · 02:10 PM

1./2. No, the gap was much bigger, I id a quick manual cheack and I could feel it lock. Obviously in hindsight I should have measured it.

In the back of my mind I was thinking that the gear couldn't wear, only the synchro could, so it had to be good. (They call this the high price of ignorance/education)

3. Nope. Se italics above. Perhaps error #2 (of many?). They looked fine, assuming you mean item 8. in the photo above (inner and outer).

4. Not sure what they are....are they in the photo above?

Peter Zimmermann · 06-17-2011, 03:19 PM

Your #3. Yes, item #8 in the exploded diagram.

Your #4. They are the item #14 pictured as part of item #8. They have a curved side, and if you had them apart they must be installed with the curve toward the operating sleeve (no number above but its the largest single part, and has all of its teeth on its inside surface).

With a worn out synchro comes other wear, to the small teeth on the sleeve, etc. You must measure the clearance between the back side of the synchro and the tips of the small teeth on the gear. I believe, for your car the new gap should be .9mm minimum, with a wear limit of .6 to .7mm. The measurement is done by simply pushing the synchro ring onto the cone so that the resulting gap is equi-distant all the way around, then use feeler guages to measure.

A measurement of the old synchro would have helped me to figure out what other issue you might have (something broken in the clamping plate, etc.), but without that this is the best that I can do.

Matt Monson · 06-17-2011, 03:23 PM

I agree with what Pete is thinking. I suspect you may need to replace the dog teeth on third gear to solve your problem.

Regards,

Matt Monson
Guard Transmission LLC

1990C4S · 06-17-2011, 04:10 PM

I am sure the curved side is out. 100%.

I guess checking the synchro gap will be step #1 in the next tear-down. Thanks for your help.

shrtshck · 06-17-2011, 04:20 PM

Ya like Boston and Bettman, I'm takin back my clutch disc

1990C4S · 06-17-2011, 06:23 PM

It's a 'dis-assembly aid', not a clutch.

1990C4S · 05-14-2013, 09:20 AM

Quote:

Originally Posted by Peter Zimmermann

With a worn out synchro comes other wear, to the small teeth on the sleeve, etc. You must measure the clearance between the back side of the synchro and the tips of the small teeth on the gear. I believe, for your car the new gap should be .9mm minimum, with a wear limit of .6 to .7mm. The measurement is done by simply pushing the synchro ring onto the cone so that the resulting gap is equi-distant all the way around, then use feeler guages to measure.

A measurement of the old synchro would have helped me to figure out what other issue you might have (something broken in the clamping plate, etc.), but without that this is the best that I can do.

Update: I have the transmission apart (again). The gap is 1.0 mm.

There is nothing obviously wrong. Not sure what to do now. Open to suggestions....

1990C4S · 05-15-2013, 12:44 PM

Is Peter Z still around?

Geary · 05-15-2013, 01:08 PM

Quote:

Originally Posted by 1990C4S

I just rebuilt my G50 (160,000 miles or so).

My issue, and the reason for the rebuild, was shifting into third; the synchro did not work.

So on tear down I found some wear on the third gear synchro. I replaced the third and fourth gear synchros and re-assembled.

Absolutely no change. I can not get into third gear when moving. I can start off in third, but I can't 'double clutch' and get into third, it simply feels like two gears that won't mesh.

Can you more clearly explain ..

Was this a problem that slowly developed in 3rd gear in YOUR vehicle? .. or is there some further history you can (or can't) provide? Was it also 4th gear?

When you say "no change", but now you say "it simply feels like two gears that won't mesh", it sounds like you now can't shift into 4th gear either.

You can shift into gear when stationary (engine running), but it won't shift into 3d (4th?) gear while driving?

Can you show a photo of the sleeve, guide, and synchro on a table? Not assembled, just the 3 major components laying there .. (It's been a while, and I don't have them here. In the cobwebs I recall an assembly issue ..)

Matt Monson · 05-15-2013, 01:15 PM

What I think Paul is referring to is the need to 'clock' the synchro to the slider. The 3 flat rectangular sections on the top of the synchro need to coincide with the balls and springs on the slider hub assembly. When the gear is not selected, the synchro is spinning with the speed of the slider, not the speed of the gear.

Geary · 05-15-2013, 01:35 PM

It wouldn't be the first time this assembly error has been made .. but a simple bench shift would have caught this issue.

1990C4S · 05-15-2013, 02:13 PM

Quote:

Originally Posted by Geary

Can you more clearly explain ..

Was this a problem that slowly developed in 3rd gear in YOUR vehicle? .. or is there some further history you can (or can't) provide? Was it also 4th gear?

When you say "no change", but now you say "it simply feels like two gears that won't mesh", it sounds like you now can't shift into 4th gear either.

You can shift into gear when stationary (engine running), but it won't shift into 3d (4th?) gear while driving?

Can you show a photo of the sleeve, guide, and synchro on a table? Not assembled, just the 3 major components laying there .. (It's been a while, and I don't have them here. In the cobwebs I recall an assembly issue ..)

I bought the car with this issue. All the gears (except third) work fine. I cannot shift into third when the car is moving. If I stop and put the tranny into third, then third gear works. It just won't shift into third 'on the fly'.

I will post some pictures shortly.

1990C4S · 05-15-2013, 02:15 PM

Quote:

Originally Posted by Geary

It wouldn't be the first time this assembly error has been made .. but a simple bench shift would have caught this issue.

It shifted on the bench, it shifts when the car is 'stopped'. It won't go from second the third when I'm driving...

Matt Monson · 05-15-2013, 02:33 PM

Almost sounds like some sort of weird shifting plate/detent issue.

1990C4S · 05-15-2013, 02:50 PM

I am contemplating buying a slider set. But I hate to spend $700 on a guess.

I will double check on the clocking. The tranny was apart before I got into it, I may have repeated a prior error....

1990C4S · 05-16-2013, 08:34 AM

Matt Monson · 05-16-2013, 10:40 AM

Your slider/hub assembly is missing the balls and springs!!!
Pelican Parts - Product Information: 950-304-061-02-M100

Click on the image and enlarge. You should see the difference from yours.

Peter Zimmermann · 05-16-2013, 11:47 AM

Quote:

Originally Posted by Matt Monson

Your slider/hub assembly is missing the balls and springs!!!

No way!!! That was just for picture purposes.............right?