Changing gears in the 4t60e.

[Hemet8]

So, with evrybodys help on here, we all have determined that my '95 Ga has a 3.06 diff, 2.95 fdr, with the 28/27 chain config. Now i understand from on the froum if i chage my drive spockets and chains to get the 3.43 ratio, the tranny will not shift out of second gear, and the computer will throw a "incorrect drive ratio" code. Is this something the dealer can fix with the codes for that ratio from GM? I am very virgin to the whole "bin file" thing, so i am wondering if they could hook up a GM tech-one, erse the bin for that ratio, then put in the one for the 3.43. Thanks for the help.

[sil]

what obd is that on the 95? 1, 1.5, 2 ?
you may have to get a custom chip addressing the vss sensor calibration in code if it were obd1 you could easly do it yourself, but im not sure about 1.5, and obd2 is something you will have to send out your chip to get it custom done by someone that works with obd2 systems, i cant off the top of my head remember the url link to any place that does obd2 tuning, maybe someone else can point you in the right direction?

can you post your pcm identification, and the broadcast code on your memcal?

[Azrael]

He'll have the OBD 1.5. I'm not sure if you'll get codes or not but your car won't shift where it usually does and the speedometer will probably read faster than you're really going. Both of which can be fixed by adjusting the vehicle speed sensor signal in the trans with something like this: http://www.granatellimotorsports.com/granspeedo.htm

Most ECUs determine shift-points while driving by comparing RPM, vehicle speed, and the throttle position. The only one of those affected by a gearing change is the vehicle speed sensor.

[sil]

thats an intresting aproach, sort of like the drac box used on gms, you can actually de/solder points inside the drac box to calibrate your vss to pcm

[eliteweapons]

I don't know of anyone that does obd 1.5 programming

[gpse3400]

You won't get a code for that. In fact there is no code for that. The computer only cares if it sees the VSS at all. It will upshift/downshift normally, you have nothing to worry about.

[SappySE107]

The cars I tune all shift by MPH, not RPM.

[sharkey]

all electronic transmissions shift by vehicle speed/rpm/tps.

[SappySE107]

That may be, but when you set it to shift, it doesnt have an RPM variable there to edit. I have seen RPM listed in places but the values really don't mean anything.