skinny z

Has anyone had any experience with 700R4/4L60 transmissions and throttle valve differences?
I've done a few transmissions swaps (into my current ride) and find that units from a TBI or carburated vehicle behave differently than those from a TPI vehicle. Despite using the same adjustment procedure, the shift points are nowhere near the same. My GM dealer offers the same TV cable for either application.
One racer I've talked to believes there is a difference in the throttle valve arm at the valve body. I thought there might be a difference in the TV valve spring itself.
Anyone with similar experience?

87zjeff

iTrader: (4)

definitely a difference in cables between tbi and tpi.

the difference in the actual shifting has to do with the weights in the governor. the tv cable only has one setting....don't try to adjust shiftpoints with it or shift feel with it.

Pro Built Automatics

The TV system is the same, except for the 4-3 downshift passage on the TV bushing can be in a different location. What is changed between the two is the shift timing valves and the governor are different, allowing upshifts and downshifts to occur at different throttle openings. The governor can have lighter inner weights and lighter outer weights. There is more to it than this, but this is the basic idea of the changes, and what it affects.

skinny z

I'll look into the TV cable part numbers again. GM says that in my application, where I went from a 1986 TPI 305/700R4 to a 1984 carbed/700R4 the part numbers are the same. As it is , the trans is from a 89 Caprice and has had a rebuild and then all the typical mods (.5" boost valve, Corvette servo, etc).
It used to shift beautifully with the proper TV adjustment procedure. It was freshened up after a season or two and never shifted the same.

skinny z

After the trans was freshened up, with no mods, the shift points were something like 6000 rpm at WOT with the TV cable adjusted as per the books. That TV cable was one of the only changes made after the original was cracked during the install however it was supposed to be a direct replacement from GM. Part throttle shifts were also too high and it wouldn't shift into overdrive until 50 mph or so. I went so far far as to install a Corvette governor ( supposedly lighter weights) in an attempt to get the shift point in a little faster. Didn't change much and I switched back.
I've purchased the Holley kickdown lever and cable bracket to ensure the cable geometry is 100% however now there is very little adjustment in the cable.
I'm going to check the cable part numbers again to be sure.
Would it be worth it to swap in a valve body from a carbed/TBI vehicle?