fedekz

So I bought a used 30k mile tranny in "great" shape from a forum member and he said it had no grinds, and shifted smooth. I had it installed, and have been thinking it was the shifter alignment for the past week or so.

So I've been messing around with my shifter, adjusting it, bought a new lower box (my old one's bushings were bad), didn't seem to help at all...

For a few days 1-6 work great, and reverse you always have to hold in gear when releasing the clutch or it grinds. Then I'll park on a level surface, and 12 hours later 1st gear instantly pops (violently at that) out and is unusable, and reverse grinds even if I hold it in.

Then I'll park it for 12 hours, come back, and its back to 1-6 working fine, and reverse working okay if I hold it in while releasing the clutch...

Any ideas? Is there anything that could have gone astray when installing the tranny that would cause this?

The tranny sat for about 6 months prior to installation, I had all the seals replaced, do you think gunk may have settled and is causing this.... would a tranny flush be beneficial?

dbgoodwin

Easiest solution: only drive it every other day!

To me it seems a bit much to be fixed by a simple flush. What year/trans, coupe/vert or z06?

Bill Curlee

Several things come to mind as I ponder your dilemma.

1. What is the condition of your CLUTCH? Does it FULLY disengage the drive line when you have it fully depressed???
Recommendation: Jack the rear of the car off the ground and set on jack stands. Start the engine, put in first gear and have some one fully depress the clutch and see if the rear wheels STOP turning. If the clutch does not fully disengage the drive line from the engine and the rear wheels are still being driven, you will have a difficult time shifting if the synchros are not 100%

2. What ATF do you have in the MN6? Hopefully its new fresh ATF.

3. How are you adjusting the shift box? Are the rubber bushings that isolate the shift box from the TORQUE TUBE in good condition?

4. WHAT shifter do you have?

5. Is the plastic isolator cup on the bottom of the shifter lever in good shape and does not have slop in the shift rod hoop in the shift box?

6. Is the connector between the shift box and the shifter shaft properly installed and torqued?

7. With the rubber boot removed from the tunnel access above the shifter, shift the shifter and see if ANY component of the shift box and shift shaft flexes or has excessive free play. It shouldn't!

Please let us know what you see on these test...


Bill

Bill Curlee

Just passing on some other modifications you can consider doing to make things a little more accurate!

Check this out:

https://www.corvetteforum.com/forums...x-upgrade.html

BC

fedekz

Hi Bill, always love and look forward to your great replies

1. I'll have to test the clutch disengagement later today or tomorrow to see if that's an issue.

2. I have new synthetic ATF fluid in there. It was from autozone, not sure of the brand. It was 1 gallon.

3. I have the z06 shift box that has the metal bushings, and the way that I'm adjusting the shift box is by placing a drill bit into the alignment hole ... My shifter alignment rod thing is missing. Once that's in there I remove the bolt going through the half moon clam, and align the shifter rod cut out as perfectly as I can to be a perfect circle when looking down the hole on the half moon clamp. Then I tighten the two bolts on the torque tube, all to 22ft/lbs. I've tried the alignment with different ways like tightening the torque tube bolts first, then the half moon clamp etc. There is a little bit of play in the half moon clamp, it feels like the entire rod from the half moon clam back to the tranny rotates just a small amount, millimeters. So when I'm torquing that bolt down it rotates the entire clamp just a small amount... Not sure if this is of any significant or not!

4. It's the stock shifter. I have a z06 lower box and just the stock upper shifter with an 8 ball as a shift ****. No short shifter or anything.

5. If you mean the black thing that rotates around and fits in the large circle opening on the shift rod then yeah it's free of debres and rotates pretty easily. It doesn't feel like there is hardly any side to side movement or slop.

6. Is the shift connector you're talking about here the half moon clamp that is fixed on the end if the rod coming from the rear of the car, that accepts the shaft of the lower shift box? I torqued it to 22ft/lbs, and there is only a little bit of rotation in it like I talked about above.

7. I don't really see anything moving around necessarily. I have my old shift box which has no bushings in the front and rear where the rod goes in and out of, and I have a new z06 lower shift box with bushings in great shape and tight along the shifter. When using the one with intact bushings 1-6 seen to work better, but would grind when downshifting from 6 to 5, and reverse felt worse with the new (good bushing) shift box.

Bill Curlee

PM SENT... Call me ASAP..

Bill

jackthelad

Year of tranny? Early boxes grind and balk when run on synthetic.

fedekz

The tranny is from an 04 z06

jackthelad

It sounds like the gears are not fully engaging for some reason. I think checking the linkage all the way back to the tranny would be my next step. Beyond that, I think I would be talking to one of the transmission shops.

BTW, very slight rotation of the rod going back is I think normal - mine does it anyway.

fedekz

Thank you for the advice! How can I check the linkage back to the tranny? Do I need to put the car up on jack stands and remove the plate that covers the torque tube from the bottom, and follow the linkages back to the tranny? What exactly am I looking for? Any slop at all?

Bill Curlee

To access the area where the rod meets the trans, you actually need to seperate the torque tube from the rear bell housing. Its connected to the tranny with a metal roll pin.

The universal joint that makes up that knuckel that connect the rod to the trans can wear and get sloppy. A buddy of mine tightened mine up by hammer and spot welding..

To access the rear bell housing area and maybe get a hand on the rod, you normally have to drop the mid pipe and the tunnel plate.

For better access, you can drop the rear cradle and TILT the drive train down! NOTE! There is a limit on the angle you can drop the drive train down... Its in the service manual and printed on a tag on the tunnel near the rearend.

With it lowered, you can see if its got a lot of slop.

jackthelad

One more thought, if you disconnect the shift rod heading rearwards from the shifter box, does it have any fore and aft play? If so, this would confirm a problem toward the 'box - maybe the rear joint as Bill says (above).

If there is no play there, sad to say, I think the 'box has problems.

Bill Curlee

I agree.. Excellent recommendation!

BC

fedekz

I'm checking right now, pulling apart the trim and removing shifter to see, I'll let you guys know!

fedekz

Just to confirm, this is the linkage you suggested checking?

https://i.imgur.com/gchRfGQ.jpg

It has very little to no movement forward and back, a mm at most before feeling like I'm going to engage into a gear when tugging on it.

The joint right behind the half moon clasp bends quite a bit when manipulating it, and the rod moves side to side freely, but that seems normal considering it would have to flex and move to install the shifter box shaft.


Here Is a which video, if I use a little bit of force I can make it move about 3/4th cm or so ... But without hardly any force it only moves about a mm. When it moves the 3/4 cm I feel like the rod is going past a threshold because the resistance increases.

http://youtu.be/uYP7_oCOagc

fedekz

Is there anything else that could cause my symptoms? Reverse worked yesterday 95% while holding it in gear, then this morning I tried to reverse about 15 times - all grinding before I could actually back up.

Then yesterday first gear kick out and grinded, but worked perfectly fine today. Some days the gears work, then the next they don't

Bill Curlee

Well,,, when a transmission POPS out of gear or doesnt shift all the way into gear,, there can be several causes:

1. Excessive play or lost motion somewhere in the shifter, shift rod and connectors that transmit that motion to the trans shift rod. You stated that you checked that.

2 Shift fork pads that are damaged and dont force the trans gear fully into gear.

3 Damaged shift dogs that once the ring is slid over the gear, it lock the ring in place until its forced to the next gear.

If, you have a solid shift box, a solid shift rod, clean fluid,,,,,, You got a BUM TRANS.

If thats the case, and you need it repaired, I can make a recommendation for an OUTSTANDING rebuilder.

Here is a post that will help you understand what is all inside the trans and how they fit together:

- C5 ragtopws6, T-56 Build (whats in my tranny?) : http://forums.corvetteforum.com/nort...-smoother.html

The person who made this post, is Rick Kim who owns RKT Transmissions.

Bill

The Big Guy

Call R.P.M. and arrange to have a turn around on a rebuilt tranny.
Easiest and fastest way to solve the various problems and get the car on the road !
Thats my 2 CTS.
The Big Guy !

lionelhutz

Mine is a high mile car and it'll kick out of 1st. If it just slips right into 1st it always works fine. If selecting 1st feels forced it'll likely pop out. And like you're describing I can't hold mine either when it kicks out. I don't know why but the shifter and linkage are OK. I looked in the transmission when it was out to fix the torque tube and the linkage and forks and syncro all looked fine so I just didn't find anything to cause it.

Your reverse is another story. Mine is fine but it's known that the linkage doesn't really move the fork and shift slider enough for reverse. People cut down the fork on one side and put a shim on the other side so it moves further.

fedekz

Thank you for all the advice everyone. I just bought this transmission so id hate to send it off to be rebuilt especially since I paid $1300 shipping included for it to be in "great" condition with no issues.

Looks like I'll be dropping the tranny again and trying to shave off one face of the reverse fork and shim the other side according to the directions in this thread. I have a lathe so it shouldn't be too bad.

https://www.corvetteforum.com/forums/c5-tech/2996284-t56-reverse-fix.html