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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
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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!
 

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I guess you didn't check pressure before pulling. Check the rooster comb for a crack. Might want to buy a new servo feed tube while it's apart. Servo piston should never have been used, a dual ring at the least but the Sonnax kit is best.
 

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Discussion Starter · #5 ·
I guess you didn't check pressure before pulling. Check the rooster comb for a crack. Might want to buy a new servo feed tube while it's apart. Servo piston should never have been used, a dual ring at the least but the Sonnax kit is best.
No I didn't check the pressure. Started doing my research after I got the trans out 😐
The trans is mostly back together now everything looks good so far. I went with the sonnax servo 20k kit, black cover. My sonnax pump gears will be here tomorrow and then I'll be able to put the pump in. I'd like to air test it. Mainly I'd like to check for leaks when low gear is applied. Also I'm still not sure what I want to do with the primer valve in the pump. It's still in service, should I block it off? I see that is what must people do. It looks easy enough, I just don't understand what issues the primer valve would cause and why you'd delete.
 

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No I didn't check the pressure. Started doing my research after I got the trans out 😐
The trans is mostly back together now everything looks good so far. I went with the sonnax servo 20k kit, black cover. My sonnax pump gears will be here tomorrow and then I'll be able to put the pump in. I'd like to air test it. Mainly I'd like to check for leaks when low gear is applied. Also I'm still not sure what I want to do with the primer valve in the pump. It's still in service, should I block it off? I see that is what must people do. It looks easy enough, I just don't understand what issues the primer valve would cause and why you'd delete.
What is holding the primer valve and spring in?
A small roll pin?
If so they break and the valve blows out and you lose all pressure...
I take the roll pin out a tap it for a 1/4" npt pipe plug so its the same depth as the roll pin.
 

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Discussion Starter · #9 ·
Update:
for the primer valve I used the method recommended by hutch on some other threads i saw. Removed the small roll pin and drilled it out to 3/16. Bought a 3/16 roll pin at ace hardware for 30 cents. Removed the sping and reinstalled the valve with no spring and the larger roll pin.
Pump is back together with sonnax gears, all the clearances look alot better with the new gears.
I thought I was done but after checking the endplay I measured .070, looks like I need to be in the .020 - 0.030 range? My drum has been machined for the roller bearing and there was no extra shims on the pump, wondering how the extra end play affected the trans. Hopefully I can get get a shim kit local at the parts store and get this back together tonight. Worse case scenario Ill have to order one
 

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Update:
for the primer valve I used the method recommended by hutch on some other threads i saw. Removed the small roll pin and drilled it out to 3/16. Bought a 3/16 roll pin at ace hardware for 30 cents. Removed the sping and reinstalled the valve with no spring and the larger roll pin.
Pump is back together with sonnax gears, all the clearances look alot better with the new gears.
I thought I was done but after checking the endplay I measured .070, looks like I need to be in the .020 - 0.030 range? My drum has been machined for the roller bearing and there was no extra shims on the pump, wondering how the extra end play affected the trans. Hopefully I can get get a shim kit local at the parts store and get this back together tonight. Worse case scenario Ill have to order one
I'd shoot for .005-.015 with a bearing.
 

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The bearings aren't made to take those loads. I have seen many case to planetary bearings fail from this which usually destroys the case as it is a smaller bearing than the pump bearing.

Put 250+ psi in a trans with. 005" endplay and tell me how it turns. Next is that this trans relies on end play for planetary lubrication.

It is pointless to make them that tight.


Hutch
 

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How's it rely on end play to lube the gear set?? Isn't that what the lube circuit through the input shaft is for??
Not arguing, but like I've said, done many with 230+psi and .005 end play and never had a bearing failure and the gear set is mint....whole thing is mint....

my personal trans had 600+ runs on it, decided to check it, was a waste of time as it looked like it was just built ...
i did put a converter bushing in it and seal because i was changing converter's a bunch getting my combo right.... It runs 7.50's @ 182 mph weighing 2250 lbs.
 

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I have spelled out some important facts. I'll leave it up to you to use it and understand it or disregard it. Yes obviously lube oil flows through the input shaft but does it just spray oil on the gears?

Powerglides are somewhat like a Briggs and Stratton lube system but running 7.50 at 2200 lbs isn't much of a test on component durability. I can tell you that I have built a few glides and I'm not just making this stuff up.


Hutch
 
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