shepss217

iTrader: (5)

So i'm trying to figure out which servo to go with while doing my 4l60e build. I know sonnax makes good stuff but how is the PATC servos? They claim like 35% more holding power over corvette servos. Anyone have any experience with them?

mrvedit

PATC doesn't make anything and IMHO over-promise and under-deliver.
If they aren't saying its a Sonnax, then it might be a cheap Chinese clone of the Sonnax.

The pro builders can confirm or correct me, but the Corvette servo with a good wide carbon band is all you need up to about 550HP. Above that get at least the Sonnax 2nd gear servo; add the 4th gear servo if the budge allows.

shepss217

iTrader: (5)

Ok well while i have you, will a billet 4th gear super holder servo and cover mate with the stock corvette servo?

shepss217

iTrader: (5)

It will have the alto red wideband with a new style ac delco input drum. I saw something about pinless servos too but dont know anything about them

mrvedit

Yes, the Sonnax "4th Gear Super Hold" servo will work fine with the Corvette servo. This is clearly stated in their product summary:
http://www.sonnax.com/parts/2473-4th...dual-servo-kit

Unless you a towing a trailer with a truck or track racing above 120 MPH, I would install the billet 2nd gear servo before the 4th gear servo because you will rarely be even close to WOT in 4th gear.

shepss217

iTrader: (5)

Ok, i'm kinda thinking i will get the sonnax 2nd gear servo then, thanks for all the info man

SteveC

I went with the "Superior" race grade 2-4 servo.

shepss217

iTrader: (5)

How is that shifting under normal driving conditions? Harsh?

SteveC

1st to 2nd hits hard, 3rd to 4th not too bad, I also have a Transgo shift kit set on the third washer .

shepss217

iTrader: (5)

Yeah see i dont want it to be too harsh under part throttle just a nice firm bump, i think i'm gonna see how the stock reacts after all the tranny upgrades and hd2 shift kit then make a decision, thanks for the input anyway

SteveC

The reason for the "hard shifting" into second and the firmer shift into 4th, is more due to the setup of the transgo shift kit (#3 washer).

GMCSIERRA5.3

Use only one washer in the 1-2 accumalator..or use the oem springs(2) and drill the 1-2 feed hole too .110

shepss217

iTrader: (5)

I'm not doing the transmission, but i will let the guy know who is building it to do that. I dont mess with transmissions haha

mrvedit

Yes. I've been told that using 3 washers can result in broken internal parts including the planetaries. Rock hard shifts are murder on your drivetrain.
As pro builder GMCSIERRA suggests, use at most one washer.
PBA (Dana) suggests using zero. Drilling the feed hole bigger will firm up the shift without the "slam" that can break parts.

shepss217

iTrader: (5)

Good to know guys, thanks

thunderstruck507

iTrader: (18)

Now that I am running correct fluid levels mine shifts nice and firm with the Corvette servo. I could actually hear the tires getting a scratch on the 1-2 and 2-3 at the track last Friday and that's on a Hoosier DOT radial.

Alto Red low clutches
Borg Warner 3/4 clutches shimmed on the tight side
wide carbon band
Trans Go HD2 kit (admittedly drilled on the large side as I didn't realize I had a fluid level issue starving the trans, not a feed issue)
Sonnax HD 2-3 shift valve
Trans Go high RPM pump kit
PCM is tuned to max line pressure at calculated torque of 300ft/lbs and higher

The car is making 438rwhp with the converter unlocked and a bit lean. I think now that its tuned it would make 445rwhp or so.

Does the billet servo serve any other purpose if the GM servo is not showing signs of weakness?

mrvedit

It will make your wallet lighter, which might improve your ET.

fastsspr

iTrader: (49)

I used the "Superior" 4 different transmissions with amazing results and i love it.