The Stovebolt Site Forums The Shop Area Engine Shop powerglide gurus unite!!!!

i just bought a 65 c-10 with the factory automatic transmission. the powerglide, when put into gear, (espeacially reverse)has a slight delay and then VIOLENTLY shifts. it moves the whole truck, this being the first automatic ive ever had, i dont know what might cause this but i know its got issues.

also, i changed the filter in the tranny and found some strange bits and pieces of broken white plastic along with some shards of black rubber gasket material. this cant be good and im sure it might be an exensive fix. what would you all diagnosis?

after changing the filter and filling it back up with atf it still had the same problems and leaks fluid from the white plastic breather valve thats right above one of the transmission cooler lines

sorry this is long but i thought the more info i gave the easier to know what the problem(s) might be. ill had it over to the pros!!

I would imagine that your tranny is old enough to have a modulator valve. That needs to be hooked up to the vacuum line at all times. I don't know if it has an affect at idle but it wouldn't hurt to check it out.

Truckernix is right. Those had a modulator. Pull the vacuum hose off at the trans. If any fluid is present in the hose or end of the modulator it is bad. Check the linkage to the throttle.

thanks for the input guys, any idea what the broken pieces of white plastic could be in the transmission pan?

I am not a transmission expert but everything but the filter assembly is made from steel. There are seals but you would recognize those.

Murdoc,
Do you have some pictures of the plastic debris?

id do ill see if i can upload them in some way or another

The biggest cause of violent gear engagement is a higher than normal idle speed. Try slowing the idle down to 550-600 RPM and see if the problem diminishes. Some of those transmissions had plastic thrust washers between the rotating assemblies, so the plastic you're seeing might be the remains of a thrust washer that's been damaged by the slam-bang engagement.

Also check the universal joints, carrier bearing (if it's got a 2-piece driveshaft) and the rear end for excessive clearance anywhere. If the driveshaft gets a good spin before all the clearance is taken up, the jolt can mimic hard shifting.
Jerry

PS: If the black plastic debris is in the form of thin strips, you've got a clutch piston seal damaged, which could also account for the hard engagement. A leak from the case vent is caused by overfilling the oil pan before you start the engine and put some of the new fluid into the torque converter. That, at least, should stop after some running time for the fluid level to stabilize. If you've got bad clutch piston seals, it's overhaul time, as driving it that way will cause the clutches to slip, and burn out.
Good luck!
Jerry

>>>>>i just bought a 65 c-10 with the factory automatic transmission. the powerglide, when put into gear, (espeacially reverse)has a slight delay and then VIOLENTLY shifts. it moves the whole truck, this being the first automatic ive ever had, i dont know what might cause this but i know its got issues.<<<<<

Ok First of all disregard the above comments on the modulator, as the modulator only controls up-shift/down-shift depending on road speed/vaccum.

Now as to what you are experiancing when shifting from park/neutral into drive/reverse......

First you need to look at the one-way sprag clutch/band..... in drive/low the clutch/band allows an internal ring gear to turn with the the sun/planitary gears for forward drive of the output shaft. When you shift into reverse, the hydraulic fluid pressure applies either a one-sprag clutch or a band to the outter surface of the ring gear forcing the planatary gears to walk around the sun gear forcing the output shaft to turn opposite direction of the input shaft, thus creating reverse.

It sounds like you either have a mechanical problem in the sprag-clutch or the sun/planatary/ring gear system in your transmission. although you could also have a problem within the valve body creating abnormally high line pressure on the hydraulic side as well..

either way you have two choices.... hold the tranny up to the phone and I'll take a look at it.... or drop me a line and lets re-build it....
Either way? It's time to pull the tranny and have it gone through... before it leaves you sitting somewhere along side a dark and lonely road... because that is exactly what it will do....

Michael

Murdoc,
Over the years I have seen alot of drive line problems that were initially diagnosed as transmission problems. I would check that out first.
As far as the vacuum modulator, if the vacuum line is disconnected or the modulator is leaking
the trans pressure will go to maximum creating a harsh engagement due to no vacuum signal from the engine. Usually when this condition exists
the transmission will "hunt" between low and high between 15 to 25 mph. The modulator works in
conjunction with the governor for shifting.
As far as a sprag clutch in a PG,there isn't one. Reverse is accomplished by a clutch pack at the rear of the transmission that stops the internal tooth gear in the planetary which reverses the rotation of the output shaft.
A couple of other things I have seen with the PG
are the priming valve in the front pump not moving freely,not stuck but moves slowly. The pressure regulator valve either sticking or the
dampening spring broke.
As far as the plastic thrust washers I don't believe they were used untill close to the end of production(1973).The only plastic that I know of is the vent cap and the speedometer driven gear. Later models used a plastic drive gear.
I agree with Hotrod Lincoln about the thin strips as being part of the piston seals. The strip you refer to is probably the lip part of the seal.By the way the direct clutch pack is the only clutch that uses lip type seals ,the reverse clutch uses a square cut seal.
I would guess the transmission is due for an overhaul if the above mentioned drive line and modulator problems don't fix it.
I am no expert on the PG by any means,but these are a few of the things I have run into over the years.

arnie

thanks for the added insight jerry. it turns out that the vacuum line for my transmission was not hooked up. it shirts through the gears alot smoother now although i still need to get the idle down alittle bit more. thanks for the help yall one step closer to making it road worthy

This discussion is awesome. There are many discussions about engines inside and out but there tends to be very little said about automatic trannies.