I have a '58 GMC 100 with the standard GM 3 speed (on the tree) manual transmission. For the engine rebuild over the winter i removed the side cover of the transmission to get the engine and trans out of the car. After engine overhaul and clutch renewal everything was put back together and the side cover was fitted back as before (or so i think) and I now have the annoying phenomenon that i cannnot shift into 1st or reverse without massive gear clashing/scraping . 2nd/3rd shifts operate nice and smooth... First I thought that maybe the clutch is not opening properly but then the 2/3 shifts should be affected as well? Even with the engine stopped there seems to be a slight "resistance" or gear meshing (hard to describe) when i put it into reverse or 1st gear. I checked and adjusted the linkage according to the shop manual and it seems to be fine... Is there anything I could have done wrong when re-installing the transmission side cover that could cause the 1st/reverse gear clashing? Or might there be something else that I overlooked The transmission shifted fine before I started messing around... Any ideas/tips as always are higly appreciated.
sounds like the clutch is not adjusted properly, or is messed up, so that it does not release fully. The transmission will grind into 1st/reverse by design, since those use a sliding gear, with no synchronizer. If the clutch does not release completely, then there is no way to keep it from grinding.
Thanks for the tip...I already adjusted the clutch to open as far as possible...maybe the new clutch disc I installed (11" like the old one) is too thick - it is quite a bit thicker than the old one but not excessively so and I put it down to wear of the old one... Maybe I should install back the old one and see if the problem is gone then...i hoped to solve the problem without taking out the trans again...
That transmission only takes about five minutes to remove There are other things that could make the clutch not release fully. First check the adjustment, then make sure you have the correct release bearing, the fork is not worn excessively, the linkage is all in good condition and all complete and installed properly. Make sure the pilot bushing is not dragging, the clutch disk is not sticking on the input shaft splines, the pressure plate is not messed up (damaged fingers, broken parts, etc), the flywheel surface is flat, etc. MAke sure the transmission is full of 90 wt gear oil.
Squirrel/Saxman were right...the clutch was not releasing completely (very minor drag, but sufficient to move the gears and cause the clashing). It seems the new clutch disc I installed was a bit too thick. As a quick measure (will have to pull the trans for change of the disc/pressure plate later) I put some 1 mm shims between flywheel and pressure plate, adjusted the clutch linkage and everything works properly now... Thanks again for pointing me in the right direction.
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