When it comes to automatics I am a bit lost. I have a 91 RS with a 700R4. Suddenly 3rd gear failed. When the car shifts to 3rd the engine just runs away. There is a little engagement, but for all intents the trans just slips away and the engine Rs run away. This trans is all stock and has a fair amount of miles in it. Since I know little about automatics, I have no clue if this means a total failure or if there could be a less costly solution. Any advice greatly appreciated. Dave Here are my specs: SMALL BLOCK BORED AND STROKED TO 383ci. PISTONS: 9.7:1 KIETH BLACK. CRANE CAM 113141 STREET/STRIP. ROLLER ROCKERS. MELLING HIGH OUTPUT OIL PUMP. EDELBROCK DUAL PLANE HIGH RISE MANIFOLD. HOLLEY 750cfm DOUBLE PUMP CARB. NITROUS OXIDE SYSTEMS, SUPER POWERSHOT 150. MSD DIGITAL 6 IGNITION MSD PRO-BILLET DISTRIBUTOR ACCEL SUPERSTOCK HIGH TEMP PLUG WIRES EDELBROCK PERFORMANCE HEADERS. FLOWMASTER DUAL EXHAUST. TCI “STREET FIGHTER” HIGH PERFORMANCE 3600 STALL CONVERTER. TCI UNIVERSAL LOCK UP KIT. B&M PERFORMANCE MEGA SHIFTER. 700R4 AUTOMATIC TRANSMISSION. GM PERFORMANCE 3.73:1 REAR GEAR. CUSTOM TUBULAR SUB FRAME CONNECTORS. 4 WHEEL DISC BRAKES.

Sounds like a 3-4 clutch pack failure, one the most common fallacies of the 700r4's. You could just replace the clutch packs, but since you have to tear all the way in to the trans to do so, might as well throw a full rebuild kit in while you're in there.

The biggest killer for these transmissions is the torque converter. I bet you have a hard time keeping the car stopped at lights.

LIke mentioned its a 3-4 clutch pack failure.

Pick a lock up torque converter, and throw a rebuild kit and Trans-go shift kit in there.

I have a TCI Lock Up Kit installed. The car holds fine in gear at stops. One freind who is knoledgable with trans said he would just bag the 700R4 and go to a TH400. Any thoughts?

Just curious, do you miss 3rd all the time, or only at WOT?

Mine did it mostly at WOT, after a few upgrades, it slips all the time now. Its definately the 3-4 clutch pack that is to blame.

TH400 is a good choice, however, the TH-350 is much lighter and can stand up to some extreme duty with a shift kit.

A 700R4 will aswell, but you need $$$ to make it that way.

If youre not set on having an overdrive, definately for for a TH350 or TH400.

The trans slips at any rpm all the time. There is virtually no engagement in 3rd or 4th. I do like the OD, but we are getting ready to add a new cam, rollers AFR heads and full length headers. This should dramatically increase the HP. I'm just not sure if the 700R4 can take it. I talked to TCI this AM and they want $2500 for a Super Street Fighter 700R4, heavy duty everything in it. TCI said that a properly built 700R4 can take up to 750 HP. The alternative (TH400/350) is about the same $$ by the time you get through with a new yoke, driveshaft and torque converter etc... I'm trying to figure out which is the best value, long term. This car as it is puts out about 325HP at the rear wheels just on the motor. I have never dynoed it while spraying the 150 shot NOS.

Sounds like what my 700R4 did,mine was a broken SPRAG,Thats what engages 3 and 4 gear in the trany.I still had 1st and 2nd,but when it would up shift to 3rd,FREEWHEELING, at WOT. If I eased in to the throttle,it would try to engage in 3rd and 4th,but would not.
Time for a rebuild with stronger parts,or you can do what I did(piss on the 700R4) I converted mine over to a RICHMOND 5 SPEED,COST was way less than a new 700R4!!!!
If you use a 350 TURBO trans,you wont need a new YOKE,If you use the 400 ,you will need a different YOKE.400 yoke(splines) are different than a 350 turbo.
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