The Stovebolt Site Forums The Shop Area Driveline Hydramatic slipping

Hey Guys, my 54 chevy 3100 235 c.i. with original hydramatic trans. is slipping when shifting from the low gear to the second. Fluid is at the full line. If I shift it manually thru the gears it seems to work properly. I called around the Chattanooga, TN. area, and nobody in this area will look at it. Any ideas?

Two possibilities- - - -either the throttle pressure is too low, or the bands need adjusting. Since it shifts OK manually, I suspect throttle pressure. Look for some mechanical linkage that moves the small lever on the side cover of the transmission as the carburetor linkage moves, and adjust it so it moves further as the throttle opens. Make very small adjustments, as a little change in linkage length makes a big difference in shift points. There are some special fixtures involved in band adjusting, and one of the adjustment procedures involves dropping the pan, so try the throttle pressure fix first.

The most common slippage happens on the 2-3 shift, as the 1-2 shift usually happens at no more than 5 MPH in most cases. The truck will hardly be above walking speed when the first shift happens, unless you're at or near full throttle. The super-low ratio 1st. gear makes up for the fact the fluid coupling does not multiply torque for breakaway from a stop.
Jerry

Jerry gave you good advice. On the driver's side of the transmission are two levers. One actually shifts it into the different ranges and the other is the throttle pressure lever. The factory adjustment uses special tools that lock the carb linkage and adjust the pressure lever in reference to the back of the transmission main body. You can dial it in by trial and error as Jerry mentioned. The rod goes through a swivel with a lock nut on either side of it. You loosen one nut and tighten the other to make the adjustments. An eighth to a quarter of a turn makes a huge difference. You can go from shifting all 4 gears in about 3 feet to the other extreme of winding way out between shifts and not downshifting when you slow down. Look through the old car manual project set up bu Keith Hardy and you will find the factory service booklets for adjustment and maintenance for 54 Chevy trucks.

Hey Guys, thanks for the great advice. I'll try adjusting today. In very small increments.

I carefully followed Greg's advice with my Hydra-Matic and it would shift from 1st to 2nd at about 7 mph and also shift fine into higher gears (and down-shift quite nicely, too - when slowing down and when making a full-throttle forced down-shift). I think I was just lucky.

http://chevy.oldcarmanualproject.com/booklets/5430sm15.html

Reporting in...Well, I also followed Greg's advice. This morning after a little trial and error, everything now works fine! I don't think it was luck. I prayed for the last two days that when I did make the adjustment that it would work. Praise God for his blessings.

I don't think you should ever rule out "divine intervention" when dealing with the old trucks. Glad it worked out for you. They are much funner to drive when they work right aren't they?

Amen to that!