Here's my background info.

Had a bone stock 305 CFI and went to a mild 325-350 hp 350 w/ carb. Before the swap, the transmission shifted perfectly and I was even to get a slight chirp going into 2nd at 4200 rpm.

On the tranny side, I changed the fluid and filter and installed a 2400 rpm stall convertor. I also did the Howell TC lock-up kit.

I adjusted the TV cable per my Chiltons manual. The tranny shift fairly hard at 3000 - 3500 rpm during part throttle operation, but it acts like it might be slipping but on the downshift side. It kind of shifts, drops down 500 rpm's and then shifts again dropping to 2500 rpms. I guess that's how I can explain it. During WOT operation, sometimes is lets loose around 4500 rpms and free spins.

My gut tells me time for a new tranny, but does it also sound like my TV cable may be slightly out of adjustment. PS - I'm using the stock CFI TV cable. Do I need the carb version TV cable - is there a difference???

 

I know they say it's a good idea to change teh tv cable with the engine, but that shouldn't account for it free spinning at 4k..

Are you sure the shifter cable is adjusted right? Maybe i's popping into neutral (i it's in O)? Otherwise I say have a shop look it over, but my guess would be it's new trans time.

 

are you using a holley carb? if so which one? I know that the 4160 and 4150 carbs require a braket that fits onto the throttle lever of the carb in order to get the correct geometry for the TV cable. running without the bracket will destroy the 700-r4 trans in about 3 months. Also.. haveing the TV cable for a carb would be best as it is a different length if i remember right. If I remember the two brackets you need are the 21-121 and the 21-95 (could be 20-121 and 20-95 can not remember if there was 20 or 21) look it up on the holey website. the parts are about 20-$30 a piece and do not come with the carbs. My L69 in my 83 camaro burned A tranny up when i switched from the quardrajet to the Holley 4160 thanks to that one little bracket

 

I have both of the Holley brackets - the one on the linkage, and the one to hold the throttle and TV cable.

 

the over-all cable length is different, but the distance between the cable mount and the end of the cable is all done by the adjustment.....

but yes, sounds to me like you need a fresh trans. - How many miles were on the old fluid? Many times with a high mileage tranny/fluid, changing the fluid can wipe out the trans....

 

110K miles - don't know if it's original or been rebuilt. Tranny was surprisingly clean when I pulled it.

I've heard about a fluid change wiping out on an old tranny before - might be my case.

 

Might just be that the new 350 lets you know, where the 305 couldn't yet. My tranny seemed fine with my 305 - but with the 350 installed, it slipped bad, everywhere. I got a deal on a rebuild - $500! Now she's a whiplash waiting to happen!