Aluminum Powerglide shifting to fast

[Guest deerhuntingal]

We bought a 1964 Chevelle with a 283 and the 2 spd Powerglide but what we noticed is that it shifts almost immoderately into 2nd. We are replacing the modulator but is there more we should be looking into?

It will not down-shift as well.

Anyone had the same problem and fixed it?

We have a Powerglide handbook and have tried a few things so I was wondering what everyone else may have done to correct fast shifting and no down-shift.

Thanks!

Edited March 1, 2011 by deerhuntingal (see edit history)

[trimacar]

I'd be interested to hear the answer to this one too.

Our 63 Corvette is also a 2-speed PG, and it shifts at fairly low speed into high, although this doesn't seem to affect the performance of the car.

We specifically wanted an automatic so my wife could drive it. Rare, but not desirable.

I used to own a '66 Mustang GT-K convertible, with the Hi-Po engine, and it too had a factory automatic, would go to cruise-ins and people would ask why I took out the 4-speed!

[Guest Guest]

Try adjusting the kick down linkage. IIRC, the kick down valve position plays a major role in controlling the up shift in a power-slide.

[Guest deerhuntingal]

Well, we are stumped. Replaced the modulator but no change. The linkage has been adjusted with no change. Guess it is time to take it in for a more extensive search!

[Guest Fitz]

I would try before spending money, to disconect the kickdown linkage from the carb linkage. On the side of the PG, place manually the kickdown lever in the full throttle position, and try the car. If nothing happen, a problem into the body valve occur. If the shifting is in a higher speed range, correct to the desire shifting speed range, look at the transmission mount, sometime, worn out mount can move the transmission and engine, and move out the ajustment.

the modulator does not affect the shifting range, is job is to change the oil pressure in acc. or climbing to the clutch pack to avoid slipping.

Hope will help.

Fitz.

www.ateliersemva.com

[Guest deerhuntingal]

Thanks for the info. We will give it a try!

[Guest]

We bought a 1964 Chevelle with a 283 and the 2 spd Powerglide but what we noticed is that it shifts almost immoderately into 2nd. We are replacing the modulator but is there more we should be looking into?

It will not down-shift as well.

Anyone had the same problem and fixed it?

We have a Powerglide handbook and have tried a few things so I was wondering what everyone else may have done to correct fast shifting and no down-shift.

Thanks!

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It's interesting that you mention immoderately. Some GM cars of the mid 70's had just the opposite problem in that the shift (1-2) came so very early (5-7 mph) for emission purposes that it rendered the car very inflexible, so much that you were forced stab the throttle for kick down.

If your car is shifting OK at wide open throttle ( governor controlling the shift ) and your line pressures are OK at light throttle controlled by the Vac modulator (which could be the problem due to wear causing bleed off) I would try and change the modulator with a adjustable type so you can tune your own upshift point for light moderate throttle applications. Make sure your vacuum signal is good (no leaks) from the intake to the modulator. Remember to that all Powerglides are not the same: early cast iron use a five element converter and newer ones use a two element converter and are made out of aluminum with different internal gearbox parts.

Try the adjustable modulator, high performance guys have been using them for fifty years.

Don