1964 Cruise-O-Matic transmission adjustment

[64ZCODE]

Hi all. I have a '64 but this may apply to other years using the cruise-o-matic transmission.

My transmission was shifting fine but the kick down was not working. Also, the shift points were at set speeds, in other words pressing on the gas would not result in the car staying in a gear longer before shifting to the next higher gear. Long story short, I followed the procedure in the shop manual and set the accelerator pedal height to 4 3/8", and then set the downshift lever rod clearance to 1 1/4". The car now downshifts and stays in gear longer when under load.

Kick down is important of course but there are diminishing returns as the motor revs faster. Stock 390s develop max torque around 3000 rpm and it falls off quickly after that, so depending on the speed of the car, it would be much better power wise to just stay in 3rd gear with the secondaries open than to downshift into second for not much benefit. I'll play a little bit with the downshift lever rod clearance to try to dial this in a bit better. Observations and ideas on this would be much appreciated.

Also, I understand that at speeds over 25mph, if you shift the selector into first gear position, then the car will stay in second gear until speeds slows below 25mph.

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[64ZCODE]

The cruise-o-matic transmission in my '64 now shifts from first to second at around 5 mph, then from second to third at around 15 mph. If I give it the gas, those shift points do occur at somewhat higher mph but it still seems low to me. Would be interested in hearing from others with the cruise-o-matic on this issue. I'm thinking that adjusting the kick down linkage might change the upshift points but have not played with that yet - what do folks think?

 

[Rottinrob]

Mine shifts from 1 and barley hits second gear before going to 3rd. Unless I get on it. Transmission is rebuilt. Any ideas how to adjust it?

 

[64ZCODE]

That describes exactly how the transmission in my 64 shifts.a good transmission shop could advise on whether it's possible to alter the shift points, I really don't know. Fortunately, the engine has plenty of torque at lower RPMs so it seems to love 3rd gear.

 

[ak7an]

You might check the vacuum modulator. This assists with shift timing. Make sure the line is in good shape, connected on both ends. It might need replaced.
Cheers
Ed

 

[OneAmongOthers]

My 1969 is the same way. Not sure if the c6 is the same as the cruise-o-matic. Recently had the transmission rebuilt and it seems the same. The shift from first to second is low. Like around 5ish mph. Then 3rd shortly after at around 15mph afterwards it will just stay in 3rd. I have to hammer down to get the trans to kick down into 2nd, but it doesn’t feel like it’s any better than plodding along in third.

 

[Rottinrob]

That describes exactly how the transmission in my 64 shifts.a good transmission shop could advise on whether it's possible to alter the shift points, I really don't know. Fortunately, the engine has plenty of torque at lower RPMs so it seems to love 3rd gear.

Yeah I'll keep you posted! I might put a c 6 I have into the car if I can't figure ot out.