Gears grinding

[Alexander]

I swapped out the Gyromatics M6 for a 3 speed manual and seem to have problems.

The gears heavily grind as I try to engage 1st. I thought it was the clutch adjustment, but that checked out to be ok. I then tried to readjust the shift rods per the book, but that did not help. The clutch defiantly works as I was able to start the car in gear and then left off of it to go forward.

Going in to 2nd then back in to 1st at times seems to help, but still will grind a bit. On the road, shifting in to 2nd then 3rd also grinds. Is this a bad synchro? What could this be?

Alex

[greg g]

either synchros or your clutch is not completely disengaging. If the input shaft is not stopped completely (basically that is what the sychros do) the gears will grind. If shifting into second while stopped makes going into 1 and reverse easier, then that indicated the synchros are trying to do thier job. However if the clutch is not fully disengaged the input will be gin to turn again causing a slight grinding.

Lenghten the adjust rod going to the throwout fork a bit and see if it helps. Making the rod longer puches the throw out further. if thee is even the slightest contact between the frction disc nd the flywheel it will spin the input making gear change grind but not transfering enough power to move the car.

Since it is easier to adjust the rod than it is to change the syncros, I would start there.

[Alexander]

I maxed out the clutch adjustment any further and I will start to ride the bearing.

I have an acess whole in the bell housing where I can see the fluid drive. perhpas check if the fluid drive is spining while my wife holds the clutch.

could the wrong visosity gear lube cause this? I would think the thicker the oil the more drag and the faster the gears stop during shifting?

I think I have 80/90w in there now.

[Merle Coggins]

I have an acess whole in the bell housing where I can see the fluid drive. perhpas check if the fluid drive is spining while my wife holds the clutch.

The Fluid Drive will be spinning as it is attached to the crankshaft. The output of the Fluid Drive is attached to the clutch. If the brakes are held with the trans in gear and the clutch engaged then you'd be able to see the clutch not spinning while the Fluid Drive housing still spins, although you'd probably have to be laying under the car with the lower pan removed to see it.

Merle

[Alexander]

The input shaft checked out to be the same length as the gyromatic M6.

I saw it as a direct swap.

perhaps it might be the synchros. Thought to check with the board for ideas befor I give up on this transmission and switch back.

Alex

[grey beard]

I vote with Shel. Something is still spinning inside the gear box or no grind would happen in neutral-to-low shift. Methinks yer clutch is not releasing, despite the position of the adjustment. Mebby the disc is in bassackwards? (Springs in the disc always must go towards the flywheel or you will get this exact problem.)

Fingers worn so you don't get full travel? If you start it in low gear and the clutch feels okay, you should be able to shift into neutral, release the clutch and then put it back into low with the clutch again depressed. If'n you can't, something in the clutch mechanism is draggin".

Let us know what you find.

[Alexander]

I further adjusted the clutch to give it even more travel. First gear seams good now. However still having problems going to 2nd and 3rd when driving.

perhaps synchros? should i try thiner oil in the box?

[55 Fargo]

Hey Shell, I have 80W 90 Castrol Gear lube in my 3 spd trans, boy am I way off the 10 weight you are quoting....Fred

[Alexander]

10W in the transmission is strang. My 46-48 manual which is esentail is the same the same transmission calls for 80W

realy not sure where to go from hear other then insall new synchros?

[55 Fargo]

My 1941 to 1948 Chrysler shop manual states 90 weight gear oil for temps above 10 , and 80 weight for temps below 10.

Vacamatic trans calls for 10 weight oil.....

[Alexander]

wow, not sure I understand the logic.

the 46-48 3 speed manual transmission calls for 80W

the 49-51 3 speed manual transmission calls for 10W ??

These are essentially the same transmissions. I think the only difference is the length of the input shaft (if the car came with a fluid drive).

Seems MOPAR has conflicting information regarding this topic.

Let me ask the question:

From a mechanical prospective, which helps the synchro do its job better, thin or heavy oil? I am thinking the thicker oil, as it will add drag to the gears to slow them down to a stop during shifts??