NPlack Posted March 28, 2003 Report Share Posted March 28, 2003 I am looking into getting a 1989 Pontiac Grand Prix with a 2.8 and the 4t60 tranny to use for a dunebuggy project. I know that the 4t60 has problems with self-destruction in weird situations (like snow) so i plan to at least use a TransGo kit to help solve this problem. I have searched all over the internet for information on the 440-T4/4t60 tranny, and have come up empty handed. I need to find as many ways to beef this transmission up using aftermarket parts, or to use internals from HD trannies (surely the v8 caddies and other HP cars had better innards on their 440-t4 trannies) so that i can build up a HP 2.8 motor or possibly a 2.8 with 3.4 pistons (not sure what that calculates to, will check later). The plans for the motor would be something as follows: '89 second gen block forged flattop pistons milled 3rd gen heads (for 10.5-11:1 compression) polished and shot-peened stock rods with ARP studs polished stock 2.8 crank custom FI intake and headers I figure all of this will be worth around 210-220 HP at 7000+RPM. Will make for an awesome sounding motor, and one sweet ride. Problem is, will the 4t60 transmission be able to handle the extra HP and high-RPM shifs? The actual load on the tranny will not be very severe, since the buggy will weigh less than 1200lbs. Thanks for any input! -Plack Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted March 28, 2003 Report Share Posted March 28, 2003 well, about the only thing you can do to a 4T60 from a N/A car is rebuild it with parts from a 4T60 out of a turbo grand prix. The 4T60 in the turbo grand prix is the same as in 2.8 and 3.1L N/A cars, just a lot beefier, like better valve body and torque converter for example. There is a shift kit on top of that, I think, but it can only be installed during a rebuild, from what I have heard. While you got the motor apart, get a crank from a 3.1L, cuz a 3.1L is simply a stroked 2.8L. I would get the 3.1L crank because of the torque gain you will see. The 4th gear on the 4T60 is very weak, but I dont think you'll be doin high speed runs in a dune buggy. If you rebuild the 4T60 with parts from a 4T60 out of a turbo grand prix it will hold 210-220HP. The stock trubo grand prixs had like 205HP and 225lb/ft which was limited. Just rebiuld with those parts and you should be good. Good Luck!!! Welcome to the board Robby 90sEraWhips 1 Quote Link to comment Share on other sites More sharing options...
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