Transmission/Clutch problem?

[dave3156]

I have a 70 Stepside with a 350 and a 3 speed transmission. When I go to downshift while the truck is moving there is a growling/grinding noise. If I wait until I am stopped it shifts into the gear I want fine with no noise. Also twice during the past week the transmission has popped out of gear (2nd both times) and into neutral on its own. Finally this morning there was a definite vibration when I drove the truck which seemed to get better as it warmed up. Any ideas?

[PanelDeland]

Non synchro 3 speed.You have a tranny that is not synchronized from 2-1.I was thinking the 70 should be but the tranny could have been swapped.I would check the carrier bearing and driveshaft for the vibration.Popping out of gear could be linkage related.There is a couple of good posts on getting it right in the FAQ's.
This will TTT for better responses.

[LMN8UR]

How long have you owned the truck? If it used to downshift, Could it be could be a synchro tranny that is worn.
Let me guess, you've still got a three on the tree too!
Is your truck a longbed with a two piece driveshaft? A quick check is to inspect the center support bearing holding the back of the first shaft, But they won't vibrate less when warm. I've broken several of these, you'll know it when they go.

[dave3156]

I have owned it for 4 years. Its a short stepside. The growling problem is new. It used to make a whinning noise when I would downshift while moving and it would go into 1st before I was stopped. Now it makes a growling or grinding noise. It was converted to 3 on the floor.I have another 3 speed with linkage which is good. Could it be low on transmission lube? Could it be clutch related? I thought someone else has probably had theirs do the same thing which is why I posted. I hate to tear it apart if it is something simple. I will probably have to do something with it soon. It still runs but I'm starting to wonder if I can trust it as I drive it 18 miles each way to work.

[LMN8UR]

I would be more concernd about the vibration. Check the driveshaft u-joints, center support bearing, the tranny out, and the diff in. If everything else checks ok, maybe removing the side cover of the tranny might be warrented.

Personnally I haven't done much 2 - 1 downshifting "See Three on the tree"

[69ChevyLB]

Try double clutching it when you down shift. Pause for a second in neutral to let the clutch out and rev the engine some. Then push the clutch back in and shift into 1st. don't let the revs fall too much before shifting . If it goes into first without any noise then its a good sign the sychro is shot.

[airdale94]

Originally Posted by 69ChevyLB

Try double clutching it when you down shift. Pause for a second in neutral to let the clutch out and rev the engine some. Then push the clutch back in and shift into 1st. don't let the revs fall too much before shifting . If it goes into first without any noise then its a good sign the sychro is shot.

Great information. I always wondered what "double clutching" actually meant.

[68gmsee]

Got the same problem on mine. Hard to shift down into 1st.

I had an old chevy II three speed that was the same way and I replaced the synchro and fixed the problem. If I remember correctly, it wasn't that hard to do.

I was told that it's possible the pressure plate can cause this when the springs weaken and won't release the clutch all the way, but I've checked the plate and the throw out bearing and it releases with no problem.

Now I need to find out who sells these. Used to be able to get them at local auto parts.

['68 longbed]

I spent half the day looking for a six cylinder clutch (10 inch) because my flywheel wont take the 11 inch clutch. went to four parts stores and had to settle on just buying the disk and throwout bearing. the bigger clutch set is appearantly readily available.

just an fyi if you run into a problem finding one or the other.