Ok, this has been bothering me for quit some time now. I have a 1991 RS with a 700R4 tranny. my friend used to gave a 1991 GTA with a 700R4, Are the transmissions in these cars geared different? The reason is this, In his car he could be running 40 almost 50mph, and gunn it and it would down shift to first, in my car i cant do more than 30 in first gear, when he would run at 70mph he was only turning about 2000 rpm's or less but i am turning around 2500 or more. Why is this? They are both 700R4, shouldnt they be geared the same, oh yea and another thing i forgot to mention is that my car has a tranny out of a 85 caprice, i found this out when i got my transmission rebuilt. sorry if this is confusing but i just got the guts up to try to explain. Thanks in advance!

 

The difference in RPM's at 70mph could be the result of two different things:
1. Your RS has a different rear axle ratio than your friends GTA (likely).
2. Your torque converter lockup isn't functioning properly (resulting in higher than typical highway rpms).

As far as the shifting differences, this could be the result of the governer thats in your transmission (from the caprice) being calibrated differently from the GTA unit. Aside from that, the 1991 unit has a lot of positive updates and is a better transmission than an 1985 unit (the '88 and later ones have a much more prosperous lifespan capability).. Oh, and to answer your last question, all 700R4's have the same internal gearing (3.06, 1.62, 1, 0.70).

 

oh yea thats another thing i forgot to mention is that we both had the same 2.73 rear end gear. And another thing is that when they rebuilt my tranny they added all the newer updates to the tranny.

 

Perhaps they forgot to change the speedo drive gear to the proper one for your 2.73 rear end...

Another possibility for the 4-1 downshift that your buddies GTA can do (which all 700r4's should be capable of performing in a limited set of parameters, though the 4-2 is more common and easily achieved) is that you have a tired and worn out throttle valve spring (commonly forgotten in many rebuilds) and you aren't achieving full TV (which will be required for some of the really nasty upshifts )..

Again though, the governor being different can affect all of this as well (part throttle shifting, and WOT max shift points)