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4 speed conversion HELP

1K views 18 replies 9 participants last post by  DUTCH MAX HEADWORK 
#1 ·
I converted my 72 ss Chevelle from a 7700r4 to an m20

I adjusted the clutch until the trans would change gears while at idle in my garage
I kept turning the adjusting rod until the trans would shift without grinding at idle in my garage

Just put on 50 miles worked perfectly and when I got to my garage the car won't shift into gear running
I have the pedal fully pressed it won't shift at idle
when the car is off it will shift all gears no problem

I think i have to adjust the rod more positive to allow the trans to shift into gear
possibly the clutch needs a break in adjustment
just wore in very strange any advice before I get under the car in the am and go at it
THANKs
 
#2 ·
I think mine has about 1 inch of free play before I feel the pressure plate. Then when I push down it gets close to the floor. Are you sure you have the right Pivot stud and or correct throw out bearing? Jim
 
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#3 ·
John, it sounds like your clutch adjustment procedure isnt accurate enough. 1-1.15" of pedal travel before engagement is right. I do the other end; i seat the clutch rod into the bellcrank fully, and then back it off a few turns. Its maybe 20-30 thou of play , at that end. Hard to get a feel for it, frankly.

I also have a small hole drilled into my bell for an "airgap" adjustment. Maybe Jody or someone can tell us how to do that one! I was told it's supposed to be 0.080" is all I know.
 
#4 ·
Might not be an adjustment issue but an alignment issue. Did you have to persuade the last inch or so of seating the trans to the bell housing? If everything is lined up correctly the trans should seat by hand will little pressure.
As far as adjustment when pedal is at the top there should be approx 1/8 gap between throw out hearing and fingers on pressure plate.
 
#12 ·
When the car is running at idle and you have the clutch pedal to the floor does the car want to still move if you don't have your foot on the brake. If you have a magnetic pilot bushing or the clearance between the bushing hole and input shaft is not enough the input shaft could have seized to the pilot bushing which would cause the transmission to not stop spinning even though the clutch is pressed in.
 
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#13 ·
I ask if he had to force the trans to seat (either clearance with pilot using or poor alignment) but OP did not respond to that question.
 
#14 ·
My .02. When I did a M22 install on my 69 camaro, I had to do a fairly significant readjustment after about 50 miles just as you describe. All new parts. Once readjusted, no further adjustments in many thousands of miles. Hopefully it's something simple.
 
#15 ·
Another thing to check is see how close to the floor the clutch is catching by pushing it in all the way and then easing it out in gear. If it's catching to close to the floor it will cause your problem also. I don't know if you had replaced the rubber bumper that the clutch pedal comes up and stops against but what they sell now are too thick. They should only be about 1/4" to 5/16" thick. Thinning them down gives you more pedal travel. It allows you to shorten the free travel which will become more by thinning the rubber bumper. You must do this which will cause your clutch pedal to catch higher off the floor. :thumbsup:
 
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#16 ·
I figured it out but have not fixed till this weekend

the m20 would not go the last 1/8 inch into the bell housing
I pulled it apart put trans and bell housing on bench bell housing was too small by a tiny bit
I believe this is because I bought the cheapest gm bell housing out there. AKA China CRAP
I hogged out the hole until the trans fit It was not precise surgery as the bell housing / trans mating area is thick

So I have a not correctly aligned issue not going in a perfectly straight line messed up the clutch trans working.
The problem is I need to get a Summit or Jegs bell housing and test fit on the bench for correct mating install.
This should solve the problem

That being said when it ran and engaged for fifty miles the 4 speed roared with the 373:1 rear gears
did not plan on that. The old trans was a 700r4 with single wire overdrive worked great for revs with the 373:1
So the plan is to sell the m20 shifter and rods on e bay and go with a T5 which leads to my new post
Has anyone done this b4 looks tricky to get the system right see you in the next POST
THANKS
 
#17 ·
PUT A THREADED ROD IN THE ADJUSTER AS THE ROD THAT CAME WITH THE KIT IS IMPORT CRAP AND won't ALLOW A NUT OR A JUM NUT ON THE TOP OF THE ADJUSTER (too short)

ADJUSTED THE CLUTCH SO THE CAR WOULD GO INTO GEAR RAN THE CAR ON JACK STANDS SHIFTER 1 AND SECOND ALL OK

DROVE THE CAR 20 MINUTES ALL OK AND THEN won't GO into FIRST HAD TO SHUT CAR OFF SHIFT TO FIRST AND THEN START WITH THE CLUTCH IN AND DRIVE THE REMAINING GEARS WOULD SHIFT. GOT HOME

Tomorrow I am going to slowly add more positive turns to the clutch put on stands and check 1 and 2 gears in and out if good I will put on the road and test hope all is well

((the last time I drove 30 minutes and would not go into first there were no jam nuts on the adjuster and it became floppy loose and lost all pedal))

This time I checked tonight and the adjuster did not move because of the second jam nuts top and bottom nuts.

My concern is I do not want to put too much positive pressure on the clutch fork But if it does not go into first the only answer seems to add positive pressure on the clutch fork till it goes into first gear my logic is added pressure slowly

Do not want to burn the throwout bearing
 
#19 ·
If you don't have an air gap between the throwout bearing and diaphragm fingers and you need to eliminate the air gap to get into first, your clutch fork angle is incorrect. You need to start over. Do a proper alignment of the belhousing, install a good pilot bushing that has .003 clearance on your input shaft, and use either the measurement method to determine the correct pivot ball height or the clutch fork angle method. If youur clutch fork angle is incorrect, no amount of adjustment is going to get you to a full clutch release without partially depressing the clutch fingers with the throwout bearing. You'll be smoking throwout bearings regularly as the throwout bearing will continuously be engaged.

I start with the measurement method, then use the clutch fork angle to verify proper installation.

I don't understand what you did to the bellhousing, but if you took a grinder to it it's most likely junk now.

You're not getting a full disengagement of the clutch. Sound like you are saying that it works fine when cold, but after it heats up it won't go into gear. This may be because the clearance on the pilot bushing is too tight. As it heats up it drags on the input shaft causing the shaft to turn even with the clutch fully to the floor. Out of spec bellhousing alignment can cause this too. Also a possibility of a bent disk or damaged diaphragm.
 
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