Powerglide servo upgrade

Woodfin · 04-13-2025, 05:10 PM

In the past, I have used the dual ring or the Sonnex upgrade, which supports the servo pin at the cover.

I think the Sonnex upgrade may be unnecessary for 575 - 600 horsepower range.

Let me hear from those of you who build Powerglides for the milder engines. What do you use for the servo?

jmantle · 04-13-2025, 05:59 PM

As most stock / SS guys like to keep the pressure down to save HP, you don't have to do much if you're running less 200 PSI. For high horsepower applications like top sportsman with pressures over 200 PSI the Sonnax High Teck servo package works well.
Sonnax has some good articles on pin bias and other servo issues on their website.

Tom Goldman · 04-13-2025, 06:05 PM

A lot depends on how much line pressure not how much engine horsepower .
If you are using a trans brake valve body and the line pressure is around 200# or more, I would definitely use at the very least the 28133HD return spring .
If you see any signs of what appears to be band slippage or overheating from shift overlap ,particularly on the middle of the band ,you might consider going to the 28821-10K ratio servo.
I have seen major improvements on band wear with that servo.
Significant enough that it can be seen on a data recording graph

Woodfin · 04-13-2025, 07:28 PM

Tom, that is the Sonnex part I have been using, so I will stay with a proven deal.

Mike Pearson · 04-14-2025, 01:32 PM

I have thousands of runs on my glide. Just has the stock type servo In it. 600 hp. Now it could not hurt to put one of the supported type in there if you have to buy one anyway

04-13-2025, 05:10 PM	#1
Woodfin Senior Member Join Date: Sep 2006 Location: Kilgore TX Posts: 519 Likes: 8 Liked 225 Times in 90 Posts	Powerglide servo upgrade In the past, I have used the dual ring or the Sonnex upgrade, which supports the servo pin at the cover. I think the Sonnex upgrade may be unnecessary for 575 - 600 horsepower range. Let me hear from those of you who build Powerglides for the milder engines. What do you use for the servo?

04-13-2025, 05:59 PM	#2
jmantle Member Join Date: Feb 2008 Location: Black Creek, BC Canada Posts: 329 Likes: 74 Liked 169 Times in 80 Posts	Re: Powerglide servo upgrade As most stock / SS guys like to keep the pressure down to save HP, you don't have to do much if you're running less 200 PSI. For high horsepower applications like top sportsman with pressures over 200 PSI the Sonnax High Teck servo package works well. Sonnax has some good articles on pin bias and other servo issues on their website. __________________ Jim Mantle U/V/SA 6632

04-13-2025, 06:05 PM	#3
Tom Goldman VIP Member Join Date: Jan 2003 Location: Allentown,PA Posts: 2,473 Likes: 878 Liked 844 Times in 233 Posts	Re: Powerglide servo upgrade A lot depends on how much line pressure not how much engine horsepower . If you are using a trans brake valve body and the line pressure is around 200# or more, I would definitely use at the very least the 28133HD return spring . If you see any signs of what appears to be band slippage or overheating from shift overlap ,particularly on the middle of the band ,you might consider going to the 28821-10K ratio servo. I have seen major improvements on band wear with that servo. Significant enough that it can be seen on a data recording graph __________________ Tom Goldman 1500 SG , 1506 STK

04-13-2025, 07:28 PM	#4
Woodfin Senior Member Join Date: Sep 2006 Location: Kilgore TX Posts: 519 Likes: 8 Liked 225 Times in 90 Posts	Re: Powerglide servo upgrade Tom, that is the Sonnex part I have been using, so I will stay with a proven deal.

04-14-2025, 01:32 PM	#5
Mike Pearson VIP Member Join Date: Mar 2007 Posts: 2,432 Likes: 608 Liked 1,900 Times in 570 Posts	Re: Powerglide servo upgrade I have thousands of runs on my glide. Just has the stock type servo In it. 600 hp. Now it could not hurt to put one of the supported type in there if you have to buy one anyway __________________ Mike Pearson 2485 SS