JMills

Can anybody help me out? Why is my powerglide transmission shifting so hard when put into reverse or Drive !

Thanks John

wmf62

idle too high?

Bill

William Buckley

I dropped my tach down to 700rpm, and I have the same problem also. I'm interested in any comments myself.

jim lockwood

When I had the PowerGlide in my '63 rebuilt, the rebuilder cautioned me that the kit was missing a Bellville washer, the purpose of which is to cushion the shock when shifting into gear from neutral.

Sure enough, once in a while when going from Neutral to Drive or to Reverse, it will go into gear with a bang.

He told me the location of the Bellville washer was somewhere in the tailshaft housing and that it was easy to add, if ever I obtained one.

This may not be the problem with your transmission, but it definitely is what's going on with mine.

Jim

William Buckley

Thanks for the information. I will ask the next person that I contact that knows automatic transmissions about this solution.

JMills

Let me know if u will!

Thanks John

rtruman

Had that problem the guy I bought it from thought it was loose U joints . It would slap into gear and shift and clunk and carry on .

My mechanic adjusted the manifold vacuum and the timing it as smooth as silk and a complete different car. The way it should shift back in the day.

William Buckley

My timing has just been checked. Will look at both manifold vacuum and the Bellville washer as solutions.

jules-57

My '66 has shifted that way since I got it back in '83. It is always a hard shift from P to R. Although idle might may have much to do with it. Will also look at the Bellville washer. There's an entire wiki page on this thing. From what I gather, it acts as a spring or shock and that makes sense that it cushions the impact.

jim lockwood

My understanding (and keep in mind I know zip-point-zero about PowerGlides) is that the one Belleville washer which cushions the F/R gear transitions is (or should be) inside the tail shaft housing. And apparently it can be added at any time..... unbolt the housing and seemingly where the washer goes will be obvious. Stands to reason, then, that its absence should be equally obvious.

William Buckley

My car is a restored coupe, and I am thinking that there is the possibility that a washer was not installed in the restoration causing this problem. Will have it put on a lift and have a competent mechanic check to see if there is one. Thanks.

rene-paul

Check the 63 shop manual, powerglide 7-35. Item #44 is called Reverse Clutch Cushion [Bellville] Spring. Location is in the main case as I see it.
Brgds,
Rene

GearheadJoe

If you also have hard shifting on the 1-2 upshift, the problem could be with the vacuum modulator. I recall that a Powerglide I had in a 1961 Impala developed a hard 1-2 upshift, and the problem was traced to the vacuum modulator.

On that car, the vacuum modulator was an easily-removable can on the side of the transmission, connected to an engine vacuum hose. The purpose of the vacuum modulator is to smooth out the shifting to make it less abrupt. Either a bad vacuum modulator or a disconnected vacuum hose can cause very abrupt shifting.

William Buckley

Thanks for the info, Joe, but the shift from 1 to 2 is smooth. Only problem is going into drive or reverse from park or neutral.

GearheadJoe

Well, I am just speaking from memory of what I was able to easily fix on an Impala about 40 years ago. The symptoms may not be quite as I recall. Hopefully someone who is more familiar with the function of the vacuum modulator can comment here. The vacuum modulator is an external part that is very easy to replace, and sometimes the only problem is a disconnected or leaking vacuum hose.

dplotkin

The vacuum modulator is there because the 'glide uses it instead of the more typical throttle valve rod mechanically attached to the throttle linkage. The purpose of both is the same, to tell the transmission how far down the driver has the gas pedal. One does it with a rod, the other with engine vacuum - both adjust line pressure in the hydraulic control circuit to control downshift and upshift timing.

If the low band on a Powerglide is adjusted too tight it will cause immediate and unpleasant engagement from park to drive and is exacerbated by a high curb idle.

Dan

William Buckley

Thanks very much for that information. I have about three different issues that were brought up by members to talk about with a knowledgeable transmission mechanic. Members here are a treasure trove of information, I appreciate the input.

GearheadJoe

On the Powerglide that originally came in my '67, there were both a vacuum modulator *and* a mechanical throttle position sensor (TPS). I've never been quite sure about the intended function of the mechanical TPS.

One thing I know for sure is that at the very end of the TPS travel (throttle pedal floored), the TPS engages a kick-down valve to force a downshift at speeds under about 60 mph.

I believe that for positions less than a floored throttle pedal, the mechanical TPS is supposed to modulate the speed at which the 1-2 upshift occurs. For example, at light throttle the upshift might occur at 20 mph, while at heavy throttle the upshift would occur at 50 mph.

When I got my '67 in 2004, I noticed that the 1-2 upshift always occurred at about 20 mph, regardless of the amount of throttle applied. I suspected that something was not working properly with the transmission's valve body. I ended up replacing the Powerglide with a Tremec TKO-600 5-speed, so I never got around to resolving the question about the proper operation of the mechanical TPS.

In any event, for the OP that is trying to figure out a hard-shifting problem, it would be a good idea to confirm that the mechanical TPS is connected and is adjusted properly. The adjustment procedure is very simple and is described in the shop manual.

I think the vacuum modulator is the prime suspect for the hard shifting, but there is probably some interaction between the vacuum modulator and the mechanical TPS.

Critter1

You are correct. The TV rod (throttle valve rod) controls the speed at which 1-2 up shift occurrs. Shorten rod to increase up shift speed.

William Buckley

Thanks for the flow of information. I mistakenly left the car with a shop that said they knew about adjustment and repair of the vacuum modulator. When pulling the unit out, they dropped a piece of the control rod down in my transmission pan. It has gone downhill from there. Without that working I had to drive the car with REALLY BAD shifting problems to an NCRS certified shop that I found. He has the car now. Lesson learned .... only use someone that really knows what they are talking about!