64 poweglide question

[Kyle Zevena]

Hoping a powerglide aficionado can enlighten me...

When I put my transmission (car is a 64 with original powerglide) into drive form park the transitions’ NOT smooth, it kinda "bangs" into place... the same is true when shifting from park to reverse. Is this likely a vacuum issue or a modulator valve issue or something else. If the modulator is suspect is there a way to test it or its effect (or lack there of)?

I have all winter to look at this myself (which is always my preference) before I breakdown and take it in next spring...

Oh p.s the car has always done this since I have owned it... I circumvent the effect by shifting quickly and letting up on the brake slightly at the moment of shift... if that make sense.

[Robert S.]

Re: 64 poweglide question

"bangs" into gear...I'll bite.

Any noises occur (clank or metalic sound) when it goes into gear?
What is the engine idle speed when in Park?
Have you checked your U-joints?
Have you checked the differential back-lash?

The answers to these questions would help diagnose the problem.

[Kyle Zevena]

Re: 64 poweglide question

Thanks for the response.

-It is not a clank or metalic sound, it just isn't smooth.

-engine idle in park is 650 RPM when fully warm (drops to about 500 in gear)

-have not checked the differential back lash (yet).

-u-joints do not have noticeable play.

[Jack H.]

Is your 'snubber' in good shape?

That's the rubber cushion on top of the rear differential mounting bracket. If it's badly deteriorated or missing altogether, a 'clunking' sound from the rear end of AT cars isn't unusual (UPC 4, Sheets B1 and B3))

[Gary C.]

Re: Is your 'snubber' in good shape?

I went through this when I was getting a car ready for a PV. Jacks suggestion was the single best improvement I made, even though the old rubber did not look collapsed. U joints helped too.

Last thing to remember is the powerglide is not a current day transmission. On its best day it might still seem a little "rough" to you.

[Roy B.]

Re: 64 poweglide question

The modulator only comes in to play when shifting from low to drive making it smooth. The rear planetary gear drum is spinning and when you put the vett into drive or reverse the (LOW BAND) stops it ,sounds like the band needs adjustment, not a big deal you can do it your self from the outside area of the trans, I would turn it in ONE turn then try driving it.
Note= if the Modulator is bad or you have a vacuum leak the trans shifts fast from low to drive. should shift at about 30 to 35 at a normal take off.