Sonnax Accumulator Valve Train Assembly

[SlammaDingdong]

Here's an interesting piece that may benefit us 4L60E tweaking junkies:

Sonnax ATVA - Heavy Duty

Before yall go rushing out to get one , i'll be a pioneer and check it out. Will give an assessment once i give it a whirl.

[rosscob]

Thanks for Pioneering it for the rest of us. It looks really good. Please keep everyone informed.

[SlammaDingdong]

First a big to Sonnax tech support. I submitted a few questions about this piece and got a very prompt and detailed response.

Q: Is this AVTA okay to use w/ a 4L60E TGo shift kit?
A: Absolutely, it will perform quite well.

Q: Which model Sonnax AVTA for an LS1 truck, with 3.73 or lower gears, TGo shift kit, Vette/Billet servos?
A: The model M-K is specifically designed for a "heavy" vehicle w/ stock 4L60E and 3.42 or higher gearing. But, the model M-K still functions much better than the stock AVTA, for lower gear applications, if the 4L60E has been improved with a TGo kit and Vette/billet servos.

Q: Should I use the AVTA spring from the TGo kit (white for Vette servo) or one of the springs from the Sonnax kit?
A: Use one of the springs from the Sonnax kit, starting w/ the 5 lb. (medium) spring. It should provide nice feeling, firm 1-2 shifts w/o light throttle banging.

Thanks to Frank Biolsi from Sonnax (not that he'll ever see this) for helping me out.

I went ahead and ordered the model M-K. Hope to install it in the next couple of weeks.

[SlammaDingdong]

Just another update on this before old Red goes on the jack stands this weekend for a final tranny tweaking.

After letting the latest PCM adjustments soak in for about 10 days i still get a consistently stout 1-2 shift at part throttle. Allen removed 100% TM and did some other magic, which i just love , but the 1-2 still needs softening. Oh well, back to the mechanical side.

General musings about this AVTA deal -

There several different AVTA valve sizes GM uses or has used in the 4L60E. The OE AVTA for a truck will probably be one of the largest valve diameter ones. The tranny pressure curve controlled by the AVTA is very sensitive to throttle input. So I guess large AVTA valve + Transgo + Vette/Billet servos can cause the banging or harsh lower RPM 1-2 shifting. There's just too much pressure on the 2-4 band.

This may explain why a TG install in an F-Body w/ 3.42 gears works fine, but the same setup will splatter your eyeballs in a 4200+ lb. truck with 3.73s. The AVTA used in a lighter F-Body would probably have a smaller diameter valve, thus okay 2-4 band pressure and good 1-2 shifting. It does make sense

Regarding some specific parts this is my general configuration/impressions at this point -

Sonnax Servo Check Valve:
- Get it, use it, you won't be sorry.
- If using vette/billet servos, make sure to drill the check valve orifice using a #31 bit (.1200").

Separator plate:
- The TG separator plate is a low cost excellent upgrade.
- Drill the 1-2 feed hole no larger than .0700" (#50 bit) unless the application dictates otherwise.
- If using the Sonnax Servo Check Valve, for a nice, firm 2-3 shift, drill the 2-3 feed hole using a #30 bit (.1285"). Do this at your own risk if NOT USING the Servo Check Valve!!!

AVTA:
- For a 4L60E equipped truck, assume the larger OE AVTA and use the Sonnax model M-K AVTA.
- Start w/ the the 5 lb. (medium) spring from the Sonnax kit, instead of the white TG spring, for vette/billet servos.

Will let yall know how it goes

[rosscob]

I really have to learn more about transmissions. That all sounded Greek to me. Thanks for the update.

[RedHeartbeat]

Good info. Now if it just works. Let us know and if it's good, post all the parts and pieces you used to beef your trans up. Did you install the 4th gear clutch apply springs when installing the TG-HD2 kit?

[SlammaDingdong]

Originally posted by RedHeartbeat@Sep 1 2005, 10:51 AM
Good info. Now if it just works. Let us know and if it's good, post all the parts and pieces you used to beef your trans up. Did you install the 4th gear clutch apply springs when installing the TG-HD2 kit?

Yeah, this AVTA adjustment is all theory at this point. Should know for sure after this weekend.

Red, are you talking about the springs in the 3-4 load release spring assemblies in the input housing? Is that the Transgo HI-RPM 3-4 clutch spring kit?

[RedHeartbeat]

Yeah, it's the last spring pack kit deepest into the transmission body. I installed it in my other truck and I never had any issues with any gear/clutch engagement. It's tricky to install since you have to tear down the trans to do it but I thought it was worth the time.

[SlammaDingdong]

Okay, finished the new Sonnax AVTA install plus some other tweeks last night. I disconnected my battery so starting the PCM learning from scratch.

Initial impressions are it worked great.

When first got it rolling last night, it held very nicely on the 1-2 but the shift actually seemed a little "blah". Put about 30 miles on it doing drive-check-drive-check getting the fluid level good. By the time that was finished, the 1-2 was good but not at all harsh/hard, especially for low RPM and part throttle shifting.

Went for another 25 mile or so mile run this morning and eureka! 1-2 shifts are just a nice "click" at low RPM/part throttle, and perfectly crisp at higher RPM up to WOT.

Since i'm using the Servo Check Valve, also went w/ a .1285" sized hole for the 2-3 feed, a little bigger than it was. This also worked out very nicely.

Not alot of time today to post the install details. Will do that later. Just wanted to file a report of my first impressions.

[GMCwantsLS1]

Nice job Jeff, sounds like you got what you wanted. Any new trannie mods to come or do you have what you were looking for?