1941 Hydra-matic down shift
July 13th, 2013, 06:10 PM
#1
rkiddo41olds
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Join Date: Sep 2009
Location: Englewood, Fl
Posts: 55
1941 Hydra-matic down shift
Anyone know what causes the Hydra-matic to clunk when it down shifts to first/low gear. Will an adjustment minimize the problem; if so what adjustment do I need to perform?
July 14th, 2013, 02:05 PM
#2
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Join Date: May 2009
Location: S.E. Louisiana, so far still in U.S.A.
Posts: 1,613
From "Troubleshooting" in the Hydramatic Service Manual
I am assuming that this is a "closed throttle" downshift condition and that no other problems exist. The troubleshooting portion of the Hydramatic transmission service manual lists 10 possible causes.
1. Engine idle is incorrect.
2. Throttle linkage too short
3. Bands need adjustment
4. Leak in rear servo release passage
5. Broken or misaligned rear servo check valve
6. Rear servo exhaust valve sticking open - possibly caused by a misaligned gasket
7. Oil passages inter-connected or not drilled in servo body and/or accumulator body
8. Valves sticking in control valve assembly
9. Internal leak in control valve assembly - possibly caused by loose screws or rough mating surfaces
10. Oil passages inter-connected or not drilled in case.
After having one for 50 years, my suggestion would be to start by changing the fluid if it hasn't been done in a while. Drain the pan and torus at normal operating temperature, and be sure to use the correct fluid. If that doesn't do any good, be sure that the rod connecting the transmission to the throttle position is adjusted properly. The service manual for the car should tell you the procedure. If that doesn't do any good, the next step is adjustment of the bands. This process is described in the Hydramatic manual and probably in the car's shop manual (I don't have one for 1941). Specialized tools will be needed for this (J2681-C, J1693-B, & J5071 for the Kent-Moore line), but the task can be done with the transmission on the car. If the condition still exists after satisfactorily completing all of the above "stuff", you probably will have to disassemble the transmission. Don't let it fall on your chest or any other body parts. It's heavy, and will cause agony. Get a transmission jack, a Hydramatic manual, the needed tools, a spacious clean place to work, and prayer if you're religious. Best wishes.
1. Engine idle is incorrect.
2. Throttle linkage too short
3. Bands need adjustment
4. Leak in rear servo release passage
5. Broken or misaligned rear servo check valve
6. Rear servo exhaust valve sticking open - possibly caused by a misaligned gasket
7. Oil passages inter-connected or not drilled in servo body and/or accumulator body
8. Valves sticking in control valve assembly
9. Internal leak in control valve assembly - possibly caused by loose screws or rough mating surfaces
10. Oil passages inter-connected or not drilled in case.
After having one for 50 years, my suggestion would be to start by changing the fluid if it hasn't been done in a while. Drain the pan and torus at normal operating temperature, and be sure to use the correct fluid. If that doesn't do any good, be sure that the rod connecting the transmission to the throttle position is adjusted properly. The service manual for the car should tell you the procedure. If that doesn't do any good, the next step is adjustment of the bands. This process is described in the Hydramatic manual and probably in the car's shop manual (I don't have one for 1941). Specialized tools will be needed for this (J2681-C, J1693-B, & J5071 for the Kent-Moore line), but the task can be done with the transmission on the car. If the condition still exists after satisfactorily completing all of the above "stuff", you probably will have to disassemble the transmission. Don't let it fall on your chest or any other body parts. It's heavy, and will cause agony. Get a transmission jack, a Hydramatic manual, the needed tools, a spacious clean place to work, and prayer if you're religious. Best wishes.
Great!
November 5th, 2023, 10:25 AM
#6
Registered User
Join Date: Oct 2023
Posts: 543
Reply
hey boss I’m having the same type issue on my 55 olds. All my gears operate but will not shift up. The car sat for a long time. I’m really hoping it’s a linkage problem but I don’t have the manual and don’t know what needs to be adjusted. I did try tightening the throttle valve linkage that’s on top of the engine but no progress yet.
November 5th, 2023, 11:23 AM
#7
Phantom Phixer
Join Date: Dec 2011
Location: Apopka, FL
Posts: 4,727
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