tranny is giving me trouble downshifting from 6th to 5th. Upshifting from 4th to 5th works fine, but it refuses to go into 5th from 6th while driving. I have to go from 6th to 4th to 5th to get it in 5th gear. when not driving it seems to downshift smooth. Anyone ever have this issue or know what the cause might be?

 

Of course, it could be a syncro but are you sure the lever is aligned correctly? Double clutch helps.

 

stock shifter so I'm not sure how to check alignment and double clutching doesn't work. seems odd it will go in fine from 4th (no grinding, nothing), but won't from 6th.

I should add that everything was fine until I missed a few 2nd-3rd gear shifts and the shifter got hung up in between 3rd and 5th.

 

If you're not sensing the syncros working or gear grinding, sounds like something related to the shifter alignment. I had a similar problem which I traced to one of the bolts coming loose between the shifter box and the torque tube when I installed the B&M shifter. I fixed it by adding Loctite Red to the bolt threads and switching from rubber to solid mounts.

Another thing to look for are torn rubber vibration isolators grommets under the bolt heads between the shifter box and torque tube. Look for excessive right- left play on the shift lever.

It does not sound like a problem with the transmission internals since you are not getting grinding or feel the syncros working. Tough to diagnose remotely.

 

that makes me feel a bit better. I was thinking it may have to do with shifter linkage since the tranny seems smooth going from 4th to 5th. I did miss some gears so it's possible I threw something out of alignment. I'm going to order a new shifter and when I install it I will look closely at everything you recommended above. Regarding the solid mounts, where did you get those and did it make a difference in noise, etc. or just made it feel a lot tighter.

 

Go to the B&M website and download the instructions on removal/replace of the shifter. B&M Shifter Installation Instructions link

The B&M shifter has solid mounts included in their kit. I would assume the other aftermarket shifter companies do also. I fabricated my own from aluminum flat stock between the torque tube mount and the shifter box and a grade 8 washer under the head of the torx bolt.

 

I ordered a MGW shifter which doesn't come with solid bushings.

 

Another thing to check is the clutch fluid level and if its clean. Is the clutch fulling disengaging?

Check the rubber bushings/grommets. You can't get replacements from GM. See the thread I started a while ago titled "Warning 6-speed owners" where this discussed in depth. As soon as I get the next batch of grommets, I'll ship you a pair for beta testing.

 

Hey Mike: Go thru the follow checks to determine which of these might be causing your issue:

1) After removing the console and sound deadening material, shift the trans into neutral. Then, use the L shaped alignment pin on the front of the box to see if it will fit in the alignment hole below it. Don't move the shift **** while doing this. If it won't fit without moving the shift **** the alignment will have to be reset. You may have multiple problems so continue with the other checks.

2) Check the torque on the T40 head bolt that clamps the shifter output shaft to the shift rod. It should be 22 ftlbs and no less. A loose shift clamp bolt can cause shifting problems. It's common not to be able to get into the higher gears or reverse due to this.

3) Check torque on the two T40 head bolts that retain the shift box to the tunnel. They should also be 22 ftlbs.

4) Remove the two bolts you just checked and examine the two rubber bushings for cuts tears or missing parts. This is common even on low mile cars and causes sloppy shifting and indexing problems.

5) Finally fix all the issues found by a) realigning the shifter with the pin b) torque all three bolts to spec. Test before reinstalling the console.

I should have a fix for the shift box bushings and likely an improvement within a week. Email me thru my profile with an email titled Corvette Shifter Solutions if you have any questions and I'll get back to you immediately. Regards, Curt

 

i have a kind of similar problem , when i shift 1 / 2 / 3 / 4 and 4 / 3 / 2 / 1 no probleme but if i shift 1 / 2 / 3 / 4 / 5 / 6 i can only shift 6 / 5 / 4 / 3 impossible to go down on 2sd gear until i totaly stop my car ... (c6 my 2006 MN6 )

and when i stop i also have to shift 2sd before shift in first gear .

well i am sure is a probleme of alignment , i want to fix by using the advice of "montereyredc6" , but because i am french i don't understand exactly , so do you have a picture to visualy explane what you tell us .

thanks , i am really embarass.

 

thanks Curt

 

Please let me know what you find was causing this problem. Thanks Curt

 

will do Curt. I won't have my new shifter until Wed so I haven't taken anything apart yet. I did a search on LS1tech and this seems to be a very common problem with the T56. Unfortunately it looks like it may be a mechanical issue with he transmission internals, but each post never had someone confirming what was actually wrong with it.

 

just got done installing my new MGW shifter...wow what a difference from the stock one. I wish I had installed this before my trip to the track. Unfortunately I still can't downshift into 5th. 4th to 5th is fine, just no 5th to 6th. I checked the shifter alignment and bushings and all check out ok (only 8k miles on the car).

I think it may be an internal issue from my missed 2nd - 3rd shifts.