Getting ready to install a corvette servo and a tru cool 40k cooler on my 4L60E

[FTTSHO]

I got a 2001 Chevy Blazer 4x4 with the 4L60E.

The truck has 112k original miles. I did a transmission flush and filter change about a year ago, and the transmission shifts and works awesome. I also sucked out 5 quarts of fluid and fill it back up with new fluid. No issues, it shifts and works great. The transmission is in excellent shape, and I want to keep it in excellent working order for a long time.

I’m going to be installing a trucool 40k transmission cooler along with a corvette servo, to hopefully keep it working good just the way it is for a long time.

What does a corvette servo exactly do? I hear it’s good because it will make the trans shift a little faster and firmer, and increase the band pressure for less slip, which should help the 3-4 clutch pack? Are these the only thing a corvette servo would do? Can someone with knowledge on corvette servos explain the benefits and potential down sides to installing a corvette servo? I don’t drive the truck hard, I just want the best for my transmission to keep it working great for a long time, because I do not want to drop the transmission and tear it apart for a rebuild anytime soon.

Thanks in advance.

 

[ls1mike]

I thought the biggest thing it did was help prevent the 2-3 shift flare in Corvettes. It will firm up the 1-2 shift but I remember reading it had something to do with the spring in the other accumulator not matching the new one. Maybe Cline will chime in but for a 4.3 S-10 I am sure I would do anything with it but keep up with a good maintenance routine and install the cooler.

 

[barkingspider]

I had a 2002 s-10 V6 bought new. Mike is correct w the firm shifts. I drove it for 5 years then my dad drove it for about another 8 years, mostly shirt tripped as his work was 5-6 miles from his house. What we did was drain and fill the trans w dex/merc every 30-40k miles and gave us no issues

 

[xmanjeff]

i have a 2003 silverado , i have heard about the corvette servo helping the 4l60 also ,
how much , and what does it take to swap in ?

 

[FTTSHO]

i have a 2003 silverado , i have heard about the corvette servo helping the 4l60 also ,
how much , and what does it take to swap in ?

There are many on eBay and Amazon for under $50. It’s easy to swap out. Just gotta make sure to put the clip in correctly for the cover, because some people don’t and they destroy the transmission by losing fluid.

 

[FTTSHO]

A little update…. Don’t want to turn this into a maintenance thread, but hear me out.

I decided not to do the corvette servo upgrade, because on my 2001 Blazer (which is very tightly packaged due to the truck being small) there is literally no room to get the snap ring off of the servo cover. I’ve tried all the flatheads I’ve got, I’ve tried picks, I’ve tried literally everything… but the exhaust pipe is in the way of getting enough room to twist the tool to remove the snap ring in there. I can stick the tool enough to lift the snap ring, but I just cannot pry on it. After trying to do it for over an hour, I decided that for me to get in there, I gotta drop the Y-pipe exhaust, which I easily could, but I do not want to risk breaking the crusty 24 year old exhaust bolts..

Just an FYI for other 4door 2nd gen blazer owners. It’s not as easy as it seems, compared to a full size truck.


But i will be installing the 40k cooler this weekend. This should be pretty easy.

I will post an update this weekend, and I will post the before and after temperature readings. The fluid runs about 195-200F with the stock radiator cooling setup, so I’m excited to see what the cooler will do.

 

[clinebarger]

I thought the biggest thing it did was help prevent the 2-3 shift flare in Corvettes. It will firm up the 1-2 shift but I remember reading it had something to do with the spring in the other accumulator not matching the new one. Maybe Cline will chime in but for a 4.3 S-10 I am sure I would do anything with it but keep up with a good maintenance routine and install the cooler.

Simply adding a Vette 2nd servo to a 4.3L isn't recommended as the 1-2 shift is usually pretty rough with a stock "553" servo.

The band clearance needs to be reduced, Cushion springs need to be added to the servo, The accumulator valve spring weight needs reduced or omit the spring altogether, & the spacer plate needs replaced (Reduce the 2nd feed orifice to .063" from stock .076" & both 3-4 feed orifices need enlarged to .093".
Also block & gut the 4th accumulator.

The reaction sunshell is a weak link it this year model....The last thing you want is a firmer 1-2 shift!!

 

[Tomioka]

Simply adding a Vette 2nd servo to a 4.3L isn't recommended as the 1-2 shift is usually pretty rough with a stock "553" servo.

The band clearance needs to be reduced, Cushion springs need to be added to the servo, The accumulator valve spring weight needs reduced or omit the spring altogether, & the spacer plate needs replaced (Reduce the 2nd feed orifice to .063" from stock .076" & both 3-4 feed orifices need enlarged to .093".
Also block & gut the 4th accumulator.

The reaction sunshell is a weak link it this year model....The last thing you want is a firmer 1-2 shift!!

https://www.transmissiondigest.com/a-new-trick-in-the-bag/
What is your thought on the 4L70E 2nd servo? Did a vette servo mod 10 years ago and been regretting the 1-2 shift feel but was thought it was supposed to help the transmission last longer. Tossed the old parts but now planning to go back to stock.

 

[clinebarger]

Tune the unit to the Vette servo.....

*TransGo SK-4L60E, Follow the directions except for the Band Release Orifice (Drill to .086"), 2nd Feed to .065", 4th to 111".
****Do Not use the TransGo 2nd Accumulator springs, Use the 2 OE ones!

*Replace 2nd accumulator piston.....
For 2nd design with legs use TransGo 4L6-2ACM
For 3rd design without legs use TransGo 4L65-2ACM

*Replace the Forward accumulator piston with TransGo 4L6-FWD

*TransGo #46-PLT-96 Spacer Plate.

*Sonnax extra long band apply pin 77787-02K, Install pin & servos with no seals, If you can't get the cover snap ring in.....Grind a little off the end of the pin.....Once you can get the snap ring in....Try to turn the output (Driveshaft) both directions, If it's locked in one direction....Grind a little more off the pin & try again. Then assemble the servo per the TransGo directions with the 2 extra cushion springs & venting the spring seat/cover, You don't have to grind those giant notches like the directions.....Four 1" cuts with a cut-off wheel will be more than sufficient.

*I recommend blocking the 4th accumulator by driving a .250" steel checkball into the accumulator feed hole in the case (The open hole in the accumulator bore).....You can now omit the 4th accumulator piston, Pin, & Spring.....The Low Reverse Clutch will now have metered lubrication at all times not just in 4th gear.

 

[Dragfluid]

I may have a few different thoughts on this. Firstly, that "Corvette servo" is way overused. The only time I recommend it is in a high HP application. What really needs to be addressed is the servo pin length as Clinebarger mentioned. I use the GM longest available pin in everything. It has no rings on the end of the shaft by the pointed end, which is smooth. The one that you have is probably two rings, which I've seen is just about everything. Check the clearance as above.
I personally don't agree with blocking the 4th accumulator. I just remove the spring.