Well i have more free time then money for once in my life so i decided I'd rebuild first powerglide. Getting ready to put it back together, a few question about what im seeing. I'd also like to say this forum has helped me tremendously, I've spent hours reading thru old discussions but I have yet to see the issue I'm having talked about. Any input is greatly appreciated!
The glide is behind a 1000hp turbo 410w sbf foxbody street/strip car. The trans is new to me. Stock case, 1.80 bte straight cut gear set, billet bte valve body, turbo spline input shaft. Looks like a stock servo. It's a single seal cast piston with an after market cover. Has a transbrake. I was told when I bought it was freshly rebuilt with only about 5 passes on it and I believe that to be true but It also sat for a few years before I got it.
Problem I was having is it would not stay in low gear. I would shift into low, I'd drive about 10 feet and then it would disengage. I'd feel and hear something hanging up or binding in the trans before It'd slip out of low and into "nuetral". I first thought I had broken a U joint, felt similar to that. Reverse and high gear worked perfectly fine. I drove up and down the road several times troubleshooting it and i had to drive back to the house in high gear everytime. Out of curiosity i decided to make a hard pull in high gear about 15 lbs of boost and it held up fine, everything felt normal. I tried a gentle 1200rpm transbrake launch and the car held on the brake and then on release of the button it drove foward a couple feet and made the same binding sound/feeling
before it went into "nuetral". adjusted the shift linkage like 20 times trying to get low to work correctly. I even Swapped out my qauter stick shifter, cable and brackets for a b&m to troubleshoot it. Im 100% confident its not a shift linkage adjustment. Before I did all this trouble shooting I had replaced a leaking pan gasket. I put about 7.5 qaurts back in it (deep pan) car was leaning fowards so know the converter still had some oil in it, this was before all the low gear troubleshooting i did. Dip stick read full while car was up to temp, checked it several times. Checked the band adjustment it was 3.5 turns out from 72 in/lbs. I did not pressure check the trans before I pulled it, really wish I did but trans is out and in peices now.
After tearing it down first thing I noticed was the Reverse clutches were burnt up really bad, there was about a 1/2" of clearance in the reverse clutches. I disassembled further and had trouble get the ring gear out, it did not want to come out easily. looking thru the reverse clutch inspection hole I noticed one of the clutches had come out of the groove and the teeth of the clutch was riding ontop of the ridge on the ring gear. (Ring gear/reverse clutch drum whatever its called.)
Idk how that's possible but it was in a bind, I had to pry it off so it'd go back into the grooves using a flat head screw driver. You can see in the ring gear picture where the teeth of that one clutch damaged the surface the clutches ride on, left a scar all the way around, you can barely feel it with your finger nail. Im debating running it as is, get it machined or just getting new ring gear if i have to. On the inside of the ring gear I noticed some small hot spots, they seem to be exactly where the clutch got jammed up but on the inside. Is this ring gear reusable or scrap? Anyone one seen this before, how does this happen?? I fully disassembled the reverse piston, cleaned, new seals air tested it. Works fine.
There was 5 reverse clutches in there. I replaced them with 5 new ones set up the same way and I got .066" of clearance dry.
Surprisingly the low gear band looked brand new, its a red band. I'm planning to reuse it.
Servo looks like a stock cast piston. Single seal. After markert cover, not sure of spring. I'm wondering if I was possibly having a servo issue. I'll have to figure out how to air test all of that.
High gear clutches look brand new. 8 red clutches, clearance measured .069 wet. I imagine it'd be slightly more if they were dry. I didn't have any issues with high gear so I'm leaving this alone and reusing the clutches. I also noticed the drum was machined for a roller bearing in between the pump housing and drum.
I disassembled the valve body completely, gaskets looked fine, no damage. It was a little dirty, not bad though. I pulled the pressure regulator out it looked fine but I cleaned all those parts really well and put it back together. I left the gaskets out and used only the plate in between the valve body. That's what I've seen recommend on other discussions.
The pump was my other concern I took measurements of the gear clearances, there in the picture below. Housing and stator surface looked pretty decent i thought. The primer valve is also still in service, seems like everyone blocks these off. Do they create issues? Should I leave it alot alone or block it in? I also just saw that sonnax sells the oem gears for $18 so I bought a set. Maybe that tighten up some of the clearances.
So to summarize all this. My concerns are still haven't figured out why low gear is not working.
Possible servo issue? I bought a sonnax 20k servo kit. Maybe that'll help.
Maybe it had something to do with the reverse clutch / ring gear issue.
Maybe low pressure from the pump? I would think high gear would slip if pressure from the pump was low.
What happened with my reverse clutches? Everything else in the trans looked new. And reverse still worked some how.
Any input is greatly appreciated!