vanimal

Hi, i'm new to the forum, and although i have a van and not an f body, i thought this place might be a good fit because of the similarity of the drivetrain. Also, the abundance of decent van forums are not anything to write home about.
I have a 1990 g20 with a 350 and a 700r4 that has 8k miles on a total rebuild. I purchased the van after the rebuild, and i recieved all the paperwork from the work that had been done. There is no warranty due to the transfer of ownership.
The tranny is really starting to act up. At first, it just had weird shift patterns, and slightly lazy shifts. It also had a slight squeal or chirp coming from the tranny between second and third upshifts.
Now, the problem has escalated. It started revving a little high off the line almost like it had a high stall TC, and it had some slight crunching or griding feeling coming from a dead stop.
Now, it revs to probably 3k before it even leaves the line, and then it eventually catches up with the motor, presumably when the pressure builds up. This is getting worse and worse, and i no longer feel comfortable driving it.
Here's some things i have done:
readjusted the tv cable
dropped the pan, inspected the fluid (looked fine), changed fluid and filter
pulled out the governor, and checked it out (looked fine as well)

At this point, i dont know what it could be. I dont know how to check line pressure, but i know i can have it checked for free at a tranny shop. I kinda feel guilty doing that as i will most likely not pay them to work on it after they diagnose it seeing that i prefer to do stuff myself.

Here are my thoughts on this so far.
These are just theorys but maybe it will help.
I think the noise i hear between second and third is the band slipping. Maybe one isnt disengaging before the other one grabs, or low pressure is causing one to slip.
This thing probably has low line pressure. It slips untill the rpm's get high enough, then it grabs. It is directly related to rpm's. if i mash it, it will roast the tire, but if i take off slow, it slips like hell.
Thanks in advance, and i'm looking forward to getting to know this site a little better. I'm planning on doing an A-Team van replica, and i'd like to add a few ponies to boot, so i see a tpi swap and some other good stuff in the future. Maybe a 6 speed down the road.

vanimal

well i was told it is most likely spanked. I pulled it out of the van this morning, and i'm going to pull it apart and attempt a rebuild. Any tips? I'd like to make it somewhat beefy. I have a full machine shop, so if there's anything i can modify or make, please let me know!

vanimal

welp, i started pulling the valve body apart, and the auxilary accumulator piston was jammed/crooked. I may pull it apart to change the clutches and bands with beefier stuff, but i'm guessing this was the issue.

FireInMe17

Well I'm glad that you figured it out without anyone's help on here. I'm glad to see that people care enough about their old vehicles to keep them running like the day they left the factory if not better. I Hope it all goes well with the rebuild if you do decide to go ahead and redo the whole thing, if not then congrats on a quick diagnosis and hopefully fix!

vanimal

Thanks, i'm pretty happy it was something somewhat obvious.
I called Dana at Pro Built Automatics and went over what i found when i pulled her completely apart. Aparently it already had the vette servo, the Beast sun shell, and most stuff looked pretty clean. I ordered a new friction/steel kit, a new band, a shift kit, and some other replacement parts just to freshen it up. I figured i'd try this one myself so i can get familiar with it.
As for old vehicles, they are the best. I've had newer vehicles, and due to my lead foot, they dont last me any longer, they just cost more to fix. I just stick to the old, simple, and cheap vehicles and my wallet thanks me for it. I usually just go through them and fix anything that is worn or seems iffy when i buy the car, then they usually last me a few years before i ever even have to touch them again. And even then, half the parts are still under warranty. How can you go wrong?

vanimal

well i did pretty much a full rebuild on her and got it back in and running. So far, so good. Did about 75 miles on it today, and hammered on her pretty good, and it behaved.