NormanNoble

Hi everyone,

I have a 1988 coupe with an automatic trans. It was originally equipped with 2.59 rear-end gears. After 15 years of tender-loving care and some minor mods, I'm happy to have finally swapped my gears.

I just replaced them with 3.07s and am pleased with the combination of increased performance, minor increase in engine RPM at cruising speed, and very slight decrease in fuel economy. This would be considered by some as a very mild change -- but that's just what I want.

With the 2.59's, I would tach appx. 1,400 RPM at 65 MPH.

After the change to 3.07's, I tach now at 1,900 RPM at 65 MPH.

Now after half a minute, the "upshift" indicator illuminates (and stays illuminated) after sustaining cruising speed (65 MPH).

The car does make it to overdrive and I was expecting a slight RPM increase. But is the upshift indicator supposed to stay on? Will it be necessary to replace the chip with an after-market chip to stop the upshift lamp from staying on?

Aside from the unwanted upshift lamp, by replacing the rear-end gears, is my ECM now getting "wrong" information and under-performing as a result of this gear change?

Any advice will be appreciated.

Thanks,

Norman

UNCLEBILL

I have a 1990 Vert and went from 2.73's to 3.54's. Did the proper VSS change and drive and driven gearing for the speedo and YES...the lite still goes on. I went thru the same annoyance and it seems that it happens to most of us. Its annoying and I may go into the dash and pull the bulb. All indications are that no problems are occuring. I scanned while driving and the torque convertor lockup happens as it should. Some people have said that you can remove the signal via the computer but I dont have the equipment or knowledge. I tried to find the right wire to cut per my FSM but that didnt work. The consensus is to live with it but damn it can be annoying.

SuperL98

Unfortunately, you have reprogram the EPROM to change way the UpShift light behaves
The stock 1988 values are below.

NormanNoble

Thanks for your replies. I'm glad to know that an EPROM swap can fix this. Prior to all this, I actually played around with an an A.D.S. then a more expensive "custom" chip I bought from Mid America. Didn't care for either. The custom chip had my timing advanced so much that the engine knocks too easily. So I'm back to my factory EPROM for now.

The swap to 3.07 gears was the last thing I'll be doing to my '88 so I'm ready to revisit another custom EPROM swap. I'm keeping my fingers crossed that I'll find a reputable programmer for this.

Some friends have said not to waste my money on another "custom" chip through the mail and say that the only worthwhile chip swap is following a dyno tune. I'm sure the dyno tune would be optimal but my mods are modest -- mostly street legal bolt-on and I wonder if I would still benefit from another mail order "custom" chip (any leads would be appreciated!)

Thanks again,

Norman
San Mateo, CA