I installed a shift kit and a trans-cooler in my 700r4 when I replaced the engine. I am now having problems with the transmission. If i shove it in 1st and punch it it will not hold first. It will automatilly shift into second. When it shifts to second it under power it will act like its sliping. Under light acceration all the gears shift fine. We have tried to adjust the tv cable severl times but to no avail. If the transmission on its way out?

Have you tried replacing the Detent cable that comes from the throttle body? IF not the cable its self could be bad. THat cable controls the whole tranny and if it is messed up everything doesn't work right. Hope this helps.

Depending on the year of your 700 tranny, they will upshift to 2nd while the shifter is in first.... pre 1987 700 trannys do this.

A larger low/reverse boost ( .296 diameter) valve will delay the up shift.

Slippaged in 2nd gear is the band slipping. THe band could be burned up , a small servo is in your tranny ..

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At the Bonneville Salt Flats... 130mph is known as First gear ...............

It Souds Like A Typical Problem most Said The 700-R4 Wasn't A Good Trans Try Checking The Actuator Spings Located To The Passenger Side Of The Trans They Were Notorious For Breaking. If You Put A Shift Kit In It Depending On How You Set It Up, Street/Strip You Remove The Springs And Put Spacers In Place (Solid) Setup. For Heavy Duty Towing You Reuse The Springs, The Springs Do Have An Effect On Shifting. Also Try Replacing The Servos On The Passenger Side Of The Trans They Put Alot More Pressure On The Bands Than The Stockers Holding It With Greater Force. If That Does Not Fix It You Might Want To Look Into A Rebuilding Kit.