CHRIS718

if it wont shift at wot without backing out it is a sign that modulated upshift delay oil psi is higher than governor upshift oil psi at the shift valve not allowing the transmission to shift .by backing off the gas you allow the governor oil to upshift the valve because you have reduced the hydraulic engine load signal transferred to the valve body via the modualor valves reading and biasing psi based on the engines vaccum signal.if you add weight to the secondary side of the governor you can correct it.you can also do this by reducing modulated upshift delay byadjusting the modulator to a lower setting or changing the 2/3 shift valve spring.always verify the governor valve is not binding also.this is assuming the transmission is in good working order.

'79ProwlerOrange

I know jack spit about trannies, so i thought id ask the masters of the corvetteforum :D

heres the problem... if i get on the gas from a stop, it does a nice hard/quick shift into 2nd, but takes a while to get into 3rd. at first i thought it was the converter slipping but now im not sure... if i shift it myself if does the same thing, unless i back off the gas while in 2nd, then shift, then nail the gas again. so under power it wont shift right.

the 1-2 shift is ALWAYS quick and strong (even on the nitrous) and the 2-3 just plain sucks. (the nitrous did make it worse)

the trans has roughly 3000 miles on it. its the original TH350, but was rebuilt with the engine 3K ago.

:confused:

Jvette73

Im not a tranny guru but maybe if you loosen up a bit on the kick down cable it might help. Also you th350 may or may not have an adjustable modulator, but the adjusting that will only effect part throttle upshift timing. Make sure the fluid is not low. Under hard acceleration its possible for the screen to suck air if the level is low when all the fluid rushes back under acceleration. That could prevent an upshift. Once you let off and hammer it again will it hold 3rd at full throttle?


[Modified by Jvette73, 9:53 PM 3/21/2004]

'79ProwlerOrange

i'll check the fluid again, but it was full last time i checked, and i know its not leaking. and the kickdown isnt hooked up. had to put on a new carb when i did the nitrous, and i didnt hook it up because i was in a hurry :banghead:

but it was doing this when i had the old carb on and no nitrous.


[Modified by '79ProwlerOrange, 8:55 PM 3/21/2004]

brooksman9

I'm no expert either, but I seem to remember having a similar problem on a car I had when I was 16 (long ago) and it had a bad modulator valve. I think... :)

Jvette73

Heres a similar topic on another forum. One person suggests to tighten the shift cable. If yurs is not even hooked up that could be the problem. By not being hooked its having an effect on line pressure maybe. Someone also stated that it wont shift up under full throttle. Im not sure if any of this is true though.
http://www.automotiveforums.com/vbulletin/t97808.html

another great place to get good tranny advice is the Trans talk section of the turbobuick forum. Theres several very knowledgable people over there that are willing to help.
http://www.turbobuick.com

Jvette73

I sent an email to a known tranny guru. I gave him the link to this topic. Im pretty sure he's a member on this forum. Lets see what he says if he posts.

duntovlives

chris is a 100% correct about the gov. that will help you a ton. also, depending on your RPM (noticed the juice), you might consider a manual valve body. this will eliminate the gov system. i had trouble w/ a 350 a couple years ago w/ the same prob. i installed an ATI manual VB, and loosend up the direct clutch, and prob cured.
if your fluid looks fine, but smells burnt, be cautioned that during high rpms (above 7k usually) the centrifical force can make the direct clutch try to apply. if your problem worsens with time, this could be your problem. you can install heavy return springs on the drum to help this. i have had to drill a hole (.060)in the drum on 400s from time to time to aid in the problem. i know a hole this large sounds drastic, i thought the same thing. but had heard about it, and ill be darned if it didnt help. (cant do it on a daily driver)
good luck-brian

'79ProwlerOrange

Thanks! i have heard of the cable problem on Syclones and Typhoons, but i didnt know if it was the same problem or not. im kinda hoping i is. :yesnod:

'79ProwlerOrange

My forum is being werid, im not getting IMs and missing posts. :crazy: This is a big help, im going to check everything out ASAP, and if im still stuck i'll get back on here. thatnks! :cool: :cheers: