auto to 5spd problems

[Blue 81 C-10]

I have installed a '96 NV3500 5 spd (removed from a LWB PU truck) in my previously automatic 1981 C-10 SWB with a mixture of new & used parts. I first tried an early used clutch/pressure plate which worked but slipped excessivly so I replaced that with a new '96 version replacement kit. The master cyl/slave(annular type) & line are the original that came with the transmission and supposedly worked when removed and appear to work now but will not disengage the clutch. I have not found much info on such a swap and what little advice I have found is educated guess work suggesting I may need to shim my brand new (early style) flywheel some unknown amount. I would prefer to shim somewhere else such as throwout bearing maybe. I'm about out of ideas. Any help would be greatly appreciated.

[VileZambonie]

What did you get the flywheel from? What's the application? Shimming the flywheel is typically a minute amount. Did you install the release bearing correctly? Many people make the mistake of improperly installing them.

Inspect slave cylinder and clutch pedal travel.
Clutch pedal travel should be approximately 8.3 inches, and slave cylinder rod should have a minimum of 1 inch travel, measured at the clutch fork.
Inspect pedal bushings for binding and excessive wear, and the fork for damage, wear and proper lubrication. Replace components that are damaged or worn.
With engine running at normal operating temperature, hold clutch pedal approximately 1/2 from floor mat, wait approximately nine seconds and move shift lever between First and Reverse several times.
If shift is not smooth, bleed system and recheck operation.
If shift is still not smooth, inspect clutch components and repair or replace as needed.

[Blue 81 C-10]

Flywheel is new 1981 factory replacement on the 350 crate motor for the 1981 C-10. The release bearing is installed as it was from the factory though it is a new replacement(this is installed on the concentric slave within the bell housing, there is no fork, thus no adjustment. There is at least 1" of travel at the master cyl, closer to 1 1/4" and it appears to move the slave/bearing by some smaller amount, (maybe 1/4") which doesn't seem to be enough to disengage the pressure plate. I have vacuum blead the hydraulics several times and no more bubbles. As is, I can't get into first or reverse. Do you have any idea how much slave travel should be?

[VileZambonie]

Do you have the 96 Flywheel for comparisson? Is the clutch from the 96?

[VileZambonie]

How did you hook up the clutch master btw?

[zieg85]

One thing that happened to me with a new pressure plate... I did not remove the rust preventative and it acted like glue and the clutch felt fine with the free play being right, it just wouldn't disengage.  My $.02

[Blue 81 C-10]

I did have the original 96 flywheel to compare, it would not fit. I had to cut a hole in my firewall and clutch pedal to mount the clutch master cyl. Also had to reinforce the area around the hole. I did clean the new flywheel & pressure plate before i installed them. They were clean. Last night I replaced the slave cyl too and that was another waste of $75 and several hours. This may take all summer to figure out but I need my truck.

[VileZambonie]

IIRC the 73-87 clutch pedal doesn't give you enough actuation. I remember someone using a 67-72 set up on theirs. Sounds to me like if you do have the release bearing on correctly you just aren't getting enough throw if you totally bled out the system.

[Blue 81 C-10]

I agree that I'm not getting enuf stroke at the master cyl. I am going to lower the connection point for the push rod a little which should help some. Is there a source that lists the right numbers for stroke length at the master and travel distance at the slave? I think I have bled the system completely, no bubbles, but it doesn't take much foot pressure to push it to the floor.

[VileZambonie]

Reverse bleed it using a syringe. Did you bench bleed it first? If you have it out on the bench measure the stroke of the master and then measure the stroke of the push rod.

[HAULIN IT]

I've had several hyd. clutch set-ups that were a real chore to get bled. Pressure bleeding was the solution...the last one we reverse bled it (Mitsubishi or something, suggested it in there bleeding procedure) once all of the air was out, they worked fine.
 I also thought while doing it "There can't be any more air in there." but there was. I wouldn't take it back apart until I had tried one of these bleeding methods. Good Luck, Lorne

[Blue 81 C-10]

I did measure the full stroke of the master cyl before I mounted it, about 1 3/8", I think I have this travel with my setup but I don't have any way to know the proper movement of the slave, it doesn't seem to move enuf. I attempted to "bench bleed" the new slave, at least fluid ran out the bleed valve so I believed it to be full. That reverse bleed sounds interesting. What kind of syringe should I use? How large? I suppose I would have to empty the reservoir first. Is there a written procedure for this out there somewhere? I do now believe there is still air in there.

[VileZambonie]

You should bench bleed the master first. Just take a large syringe easy if you know anyone who works in the medical field. Take the cap off and fill the syringe. Burp the air and push it through the bleeder upward. Just clean up any brake fluid you spill because paint and brake fluid is a bad mix.

[Blue 81 C-10]

If the bleeder you mention is the one on my slave cyl. it isn't shaped like a normal old alemite type. It looks like an extra long hex nut, maybe 3" long except inside is smooth where threads would be so I'm not sure how to attach this syringe to it (see photo). I would like to try this method but it is already in place and I would prefer not to have to remove the transmission again for the 5th time, if I can figure a way to do it in place.

[VileZambonie]

You should be able to attach a hose. Here is the factory bleed procedure

CAUTION: Never use fluid which has been bled from a system to fill the reservoir. It may be aerated, have too high of a moisture content and possibly be contaminated.

PROCEDURE


Fill reservoir with new DOT 3 brake fluid GM P/N 1052535 or equivalent, do not overfill system.
Press and hold down clutch pedal.
Open bleed screw to expel air, (located on side of transmission above the quick connect coupling).
Close bleed screw and release clutch pedal.
Repeat procedure until all air is out of system, noting the following:
Check and refill reservoir as needed during bleeding so air is not drawn into system.
After bleeding, pump clutch pedal several times. If clutch engagement is not satisfactory, repeat bleeding procedure.
If this procedure is unsuccessful, perform the following:
Remove reservoir cap, then pump pedal very fast for 30 seconds.
Stop to let air escape.
Repeat as necessary.