Rough shifting 4-speed?

[TwoFiftyShifter]

My 87 K20 has the SM465 behind a 350tbi and 12" clutch. A pretty beefy setup and a heavy truck trans, but is it supposed to be such a bear to shift?
You can never be in neutral and go to creeper or reverse without tons of grinding, but going from 2-3-4 to one of those is fine. When rolling, you cant bring it down to 2nd without being in 3rd, or pulling down hard. and sometime downshifting from 4th to 3rd at 35ish mph takes a hard push. The reason I ask is our severly trahsed 72 plowtruck with the same tranny is alot easier to shift....

[cableguy0]

low and reverse are not synchronized in those trannies. you are supposed to be stopped to get into either gear.

[TwoFiftyShifter]

I am at a dead stop anytime I go for either of those gears. Maybe I need a throwout bearing.

[cableguy0]

do this. next time your sitting still put it in 1st gear. then shift to low i bet it goes right in. same with reverse. sometimes the gears will be out of sync and you cant get em in but shifting to 1st gear will get things lined up. also you could try adjusting the clutch to get more push on the pedal

[Pyrotechnic]

When you shift to a higher gear, then into low and reverse what you are doing is stopping everything spinning in the transmission which is why that trick works. It's possible the clutch may be dragging ever so slightly even with your foot pushing the clutch as far to floor as it would go. Might need to be adjusted.

Also, my friend encountered one of these that had been filled with automatic transmission fluid...it didn't work all that well and was noisy. Once they drained the atf and put the proper lube in, it worked great.

[TwoFiftyShifter]

That's what I was saying, you need to be in another gear to go to reverse or low, I was just checking if that was normal... But pulling down to 1st from N even at a dead stop is kinda hard usually unless I jiggle the clutch.

[ont_guy_38]

As posted by a couple others I would try adjusting the clutch

[ToughBowtieTruck]

Clutches are hydraulic on an '87 factory. I would inspect your fluid levels and see if you have any leaks in the system, or try bleeding it.


Also don't run with the front hubs locked in 2wd, at least for my '77 with the 205, it makes the transmission harder to shift because the resistance in the 205/rolling resistance in the truck itself changes when trying to shift it.

To shift these properly:

1.Push clutch all the way down.

2. Hold the shifter (not forcing it) against the gate of either 1st or reverse. Shouldn't grind but might not go all the way in.

3. Easily release the clutch to let the transmission gears syncronize-might grind a little bit, but push the clutch back in and it will go into gear.

80s shifters are also different from the 70s. Most 80s shifters are a lot tighter and have less play in them than the 70s shifters. You could also be experiencing this . . .

When trying to go into 2nd, you need to help time the speeds of the transmission (the drive shaft is turning) and the speed of the engine. Try pushing the clutch down slowly a little bit while holding it in the 2nd gear gate and it should shift. Sometimes you need to rev the engine up to get it to shift. Learn where the engine speed and speedometer is at when shifting into 3rd. Then remember where you need to move each to get it from 3rd to 2nd or from neutral to 2nd without issues.

Also, if you have 4.10 gearing, it is almost impossible to shift into 2nd because the truck runs so slow in that gear anyhow. You either have to stop or rev the engine up some to help it syncronize.

As a Class A semi driver, I have driven many transmissions that you either time the speeds to shift without clutching or have to double-clutch to get the speeds to match. Most of the time I can just straight shift my '77/465 without the clutch at all.

Originally Posted by Pyrotechnic

Also, my friend encountered one of these that had been filled with automatic transmission fluid...it didn't work all that well and was noisy. Once they drained the atf and put the proper lube in, it worked great.

GM actually put ATF in some of the transmissions to help with fuel mileage, however the transmissions liked to burn up easier....

Also with the proper 80w-90 weight it will shift a little harder cold. Don't run anything higher than 90 weight--some people do, and it kills the transmission when cold and the arm trying to drive it.