Previously posted problems with my 91 trans.(113900 miles on the clock) I took the car to a trusted trans repair shop on Sat. The owner took it for a ride and told me the trans was working fine. Now shifts 1-2 at 12mph (old was 18-21), 2-3at 20mph (old was 28-32), converter lock out a 33 and 4th at about 41mph (old was 48-51). All shifts now slide into gear instead of the neck snap shifts I used to have, especially between 1-2. He did suggest that I change the fluid and filter. It is due in about 6000 miles. I thought I would do this coming weekend. So a couple of questions:
1 - with this miles on the orig. trans, would it be smart to run Mobil 1 ATF?
(have been running Castrol)
2 - is there an adjustment somewhere to alter the shift points and valve pressures to give me back the "neck snap" shifts
3 - can drilling and tapping a hole for a brass plug in the converter to drain radically change the balance or hurt the converter.
As always, I am looking forward to replys from the best forum out there.

 

Sounds like it's shifting correctly to me. If you're under harder accelaeration the shift points
will be later. As far as the neck-snaps, has anything changed on the car recently? As for
running ATF, I cant comment but drilling a hole in the TC....bad idea... Risky business.

 

I'm a little confused. You detail differences in shift characteristics, as though you had a rebuild, but you ask about a fluid change in a trans with 113900 miles on it. Is this a new or old trans? Since most of the post seems to deal with a new trans, this response is directed at that situation.

It sounds like you got a good (?) generic rebuild. My guess is that you no longer have a "Corvette" transmission.

1) No advice or opinion.

2) No. Shift points can be altered by changing the weights and springs in the governor. Line pressure and shift firmness may be restored by installing a "shift kit". Some of the shift firmness is provided by the Corvette, only, servo. My guess is that you no longer have one.

3) Balance can be severly upset by drilling and tapping a drain hole in the converter. I HAVE heard of drilling and tapping TWO holes, 180* apart to maintain balance.

RACE ON!!!

 

The shift points & shift feel you describe are at part throttle so they can be adjusted with the TV cable.

Locate the tang on the cable retainer on the left side of the plenum and mark the current TV cable location as a reference. To raise these shift points & firm up the shift feel: depress the tang, move the cable head a few clicks toward the firewall and release the tang. Then test drive the car to see if the change is as desired.

In some cases there will be no more adjustment latitude and going to WOT will reset the TV cable; in this case it may be necessary to loosen and move forward or to bend the cable retainer (attached to the side of the plenum) slightly to maintain the adjustment.

 

Thanks for the replys -
Unriced-the only thing that changed was the TV cable adjustment - reset to factory

EFI-CFI - no, the trans has not been rebuilt (to my knowledge) I bought it 4 1/2 years ago w/85,000 miles. Have changed ATF 2x (every 25-30,000 mi)

65Z01-I have played with the TV settings but fearfull of going to far 1 way or the other. Have moved the cable as far as 4 "clicks" toward the front of the car without any changes to shift characteristics. Have not tried to move toward the firewall.

Thanks again guys

 

Subman, I can tell you this... I had a "delayed" shifting issue.

Moving the cable towards the firewall (moreso than I thought I should, also) solved it.

So if the cable gives you the play, go for it and see what happens. If you're not

forcing anything and dont feel anything kinking or grabbing, you should be good.

 

Moving the TV cable towards the FIREWALL will raise the line pressure AND raise the shift points.. a LITTLE. It will also cause the transmission to shift a little "harder".

Don't worry about getting it too far back. When you go to WOT it will rachet itself forward to the proper position

Moving the TV cable too far FORWARD can cause you ALL kinds of trouble.
Mostly it will lower line pressure, cause the transmission to upshift way to soon, and burn the clutch packs because the pressure is too low for them to engage without excessive slippage and cause your tranny to become a space taker in your garage a lot sooner than you want.

So, if you want to play with it, go ahead. Just move it in the REAR direction and see how you like it. THis way you won't hurt it.

The REAL way to adjust your shift points is with the springs and weights on the transmission governor. A REAL PITA. I don't think you really want to do it but at least now you know what to do if you want to. (These kits are available for about 35 bux) it's just a PITA to get the governor cover off and the governor out/in with the tranny in the Vette.

Oh, don't worry about draining the TC. Just go ahead and change the fluid and filter. Drive it about a week. Go to your auto parts store and get one of those little hand pumps with a long tube on it.
Siphon the fluid out of the tranny and refill it again with fresh fluid.
That'll be better than most folks do.

I also would NOT change up the type fluid you are running in it.
Not that you have a lot of miles on it but whatever detergent package the fluid you have been using has, you may want to stick with.
No need to loosen up a lot of stuff/grime/varnish in there and have a checkball or something stick afterward. Just use what you've been using.

It'll probably run another 40,000 to 50,000 miles without a rebuild. Maybe more.

Good luck with it.

 

Moving the TV cable toward the front (nose) of the car is what has lowered your shift points. Reset it back to factory spec by depresssing the tab and pulling all the way back, then go inside and open the throttle all the way, it should ratchet out some. Drive it and if it is still too soft or too soon, move the TV cable backwards a few millimeters, drive it again, see how it feels, and so on and so on until you get it the way you like it.

 

Just a few clicks (certainly 4 clicks whould be enough) toward the firewall should make a noticible difference in shift points as well as shift feel; if not possibly the cable is broken or the ball has dropped off. In either case this would require immediate service as low line pressure will take it's toll on the tranny. If this is suspected, your tranny shop can easily check line pressure.

If you know the prior WOT shift points, recheck then now. If they too have lowered you may need some governor work done.



[Modified by 65Z01, 1:25 PM 9/30/2003]

 

to do an entire fluid flush, do not drill into the torque converter.
disconect the exit line from the transmission cooler, this is the top line on the radiator. insall a hose barb and atach a fiew feet of hose. make sure you have 4 or 5 quarts of oil in the pan. start engine and fill as many quarts into trans until the fluid comes out of the hose clean.

 

I love this place! - Where else can you get this kind of info AND concern over your car?
Thanks to all!
Will check as much as I can over the next couple of days and will let y'all know the outcome after Saturdays fluid change.
:cheers:
Subman