white1991rs

I was wondering, people that have done this mod, would you say it's worth it? Any difficulties installing or things I should know before I do this? This site http://sethirdgen.org/servo.htm Does a pretty good job of explaining the swap I just wanted some more opinions.

Ron U.S.M.C.

In this thread read post #7 and #9
They talk directly about the Corvette servo.
= https://www.thirdgen.org/forums/afte...rth-doing.html

If your transmission is on its way out or in just poor shape there’s no guarantee it will help.

paulo57509

I'd say it's worth doing if anything for the improved shift feel.

This probably belongs in the Transmission section, but the instructions that were included in the servo kit I ordered from Pro-Built describes grinding four drain back slots in the steel cover which most other instructions don't mention.

khulsebus

iTrader: (2)

It'll increase the pressure for the 2-4 band, but it's an easy upgrade since you don't have to remove the pan to do it, and very little chance of anything going wrong.

Ron U.S.M.C.

I also bought my Corvette servo. from them many years ago and I have never heard of doing that. Call Dana at Pro- Built and ask him.

khulsebus

iTrader: (2)

The corvette servo won't do any of that by itself, all it will do is increase the holding pressure of the 2-4 band. In order to get a better shift feel or anything else, you need to take the pan off and mess around with the valve body (i.e. shift kit), increase the line pressure, or some of the other tricks. However, the servo is often a part of other transmission work.

zenish

if this is what it does why isn't in all 700r4s?

paulo57509

....and ask him what?

Here's the instructions that came with my Pro-Built kit:



Another handy tool to have:

khulsebus

iTrader: (2)

The easy answer, the corvette had slightly more power than the other cars. The slightly longer answer, car manufacturers will trade their trade their grandmothers to save a quarter on each car. If a part will do the job, and it will save them money they will do it. My father had a friend who was involved in designing that transmission, and we talked when I was building my first 350. There was a lot of trial and error in the early 700's, and a lot of bugs that needed to be worked out over the years. From my time working in a shop before I joined the army, we built several 700's and there are quiet a few tricks to do in order to build one for performance. On almost every one that we did, the Corvette servo went into pretty much every one, as well as valvebody work to decrease shift time and a cooler to decrease fluid temp. Roughly half got a new pump, and had the governor would get tuned as well. Every transmission was run on the transmission dyno before it went out the door. I'm not saying not to install it, just don't expect it to deliver miracles.

Ron U.S.M.C.

.I just got off of the phone with Dana at Pro Built Automatics and he said that the grinding aspect of the Corvette servo is done inconjunction with one of his shift kits and he usually includes that in his directions. I did not grind mine back in 2007 because at that point I had no intention of installing a shift kit. Besides I believe that you should do the Corvette servo upgrade before you do a shift kit so you can measure the difference each makes with the install. As I said earlier the servo up grade is all that I needed with my 1989 700r4 transmission. If yours is in good shape you will feel a difference.

white1991rs

Mine is in good shape (50,XXX miles). Now I am debating on whether I should do just the servo or the servo and shift kit. Anyone have recommendations? I've always been skeptical of shift kits because my buddy had one that used to slam the transmission between gears, a proper one wouldn't do that right? Im looking at https://www.700r4l60e.com/store/home.php?cat=65

Ron U.S.M.C.

I believe that you should do the Corvette servo upgrade before you do a shift kit so you can measure the difference each makes with the install.

Reid Fleming

iTrader: (2)

I have the street/strip kit from the link mentioned. It will NOT slam the gears. It's a faster shift. But not a harder shift.

A quick story for you. When I brought the shift kit to the transmission shop, the owner of the shop said are you sure you want this installed? (He saw I had a TransGo box in the back seat). I said "Yep. Just follow the custom directions inside."

So they put the shift kit in and followed all the instructions. There is a part in the TransGo instructions that says
For firmer 1-2 shift: drill .093 to .096
For firmest 1-2 shift: drill .101 to .110

But.... Pro Built Automatics' instructions say
For stock converter drill .073 to .086
For 10" or smaller converter, drill .093 to .096
(There is no mention anywhere of drilling .101 to .110)

The shop owner looked at the above and said who ever wrote that up knew what they were doing. Because those "firmer" and "firmest" settings are really more like "crazy" and "insane." We've had a lot of people come in and get the harder settings and they end up coming back in a week and asking to make the car shift softer.

I had a stock converter and wound up getting it drilled .082

They took my car out for a test drive after install and then took me out for a test drive. He said this particular setup was the nicest TransGo he'd ever installed. He was quite curious where I got the shift kit and who made those custom instructions.

I'd highly recommend the Pro Built Automatic street/strip shift kit. It's easily daily drivable, yet has exactly the performance you want when you want it.

Ron U.S.M.C.

You don't mention if there was a Corvette servo ?

Quote = "It will NOT slam the gears. It's a faster shift. But not a harder shift."

That means that the shifts have a certain amount of slippage.

With a larger servo you get a harder shift because the clutch plates grab faster eliminating the slippage that comes with a smother shift. The only way to get away from a hard shift is to have slippage and that is harder on the plates because of the heat involved in slipping.

A certain amount of slippage is necessary for a smoother ride if that's what you’re looking for.

Side note = Even when the plates grab hard it is not as extreme at lower RPMs cruising as it is off the line at W.O.T. and that's the way I like it.
You also have to remember a large percentage of performance is coming from the ring and pinion ratio when it comes to the effect a harder shift is going to have on the way the car acts. You’re not going to exactly bark tires with a 2.73 ratio. Unless you’re running a large amount of torque.

Reid Fleming

iTrader: (2)

The Pro Built kit comes with a Corvette servo.

My car is a 1989 700R4. My parent's Corvette is a 1989 700R4. When my car was stock, it shifted differently from the Corvette. The Corvette was always a bit more of a snug shift. Hard to describe really. Just better. I don't know if this was from the Corvette Servo or if it was that the Corvette is lighter.

Having said that, the Pro Built shift kit was a whole new ball game. I remember taking my Dad out for a drive in it and showing him the various things it did. He's a gearhead from way back when. He liked it. Yet for just driving around normally, it was smooth enough that my Mom said this was no problem at all. (Women universally hate hard shifting cars)

My kit was the $149 one listed at the bottom of the page.

Reid Fleming

iTrader: (2)

It's a balancing act isn't it. The Corvette servo is a popular mod on any engine. Everything from 305 to modded LS1. Would I recommend it by itself? Sure. It's only about what, $30? (I think the 4th gens already come with the Corvette servo, but if you were putting an LS1 in a 3rd gen, you'd need it)

But for $150-178, the shift kit is a good value. It cost me 2 hrs of labor to get it installed.

Beyond the Corvette servo, the next step up would be the Sonnax servo. If I were running an 11 second car, I would probably go with the Sonnax. But for a stock to moderately modified street car, the Corvette servo is the right choice.

khulsebus

iTrader: (2)

No. Again, the only thing the Corvette servo does is give more 'holding pressure' to the 2-4 band.

Ron U.S.M.C.

You're telling me that I'm not getting firmer shifts with a Corvette servo ?
That holding pressure is instant and creates firmer shifts . It MUST because it was an "instant" improvement over the slip it had before.

khulsebus,
Do you even have a Corvette servo ?

1gary

True the vett servo makes a improvement,but TCI's design is huge in the surface area is so much better.

TTOP350

iTrader: (8)

The corvette servo started coming standard in 93 f-bodys. (I think)
I'm running the big billet part in my trans with a huge converter.

http://www.ebay.com/itm/700R4-700-4L60-4L60E-4L65E-4L70E-SONNAX-Super-Hold-Servo-Combo-Kit-2nd-and-4th-/350541961889?pt=Motors_Car_Truck_Parts_Accessories&hash=item519deddaa1&vxp=mtr

khulsebus

iTrader: (2)

Look guy, by design, the only thing the servo does is apply the 2-4 band. Now which servo you have aids in how well that band holds onto the drum. The Corvette servo has a bigger pressure area on it than the standard servo, this puts more pressure on the band, which holds the drum for gear 2 and 4. Perhaps your seat of the pants experience feels like you are getting "firmer and faster" shifts, but fact of the matter is that the only thing happening with this is that your band has more pressure holding it. The only thing that would make it "firmer or faster" is if the rod length wasn't correct. I know this from talking to the guy who designed the 700R4, he was a friend of my father from when they both were in college in Iowa. I'd get him involved in this, but he passed away a few years ago while living in North Carolina. In addition to this, I've had more 700's apart to bare cases and entirely rebuilt than I can remember. Obviously by now you are not going to believe what I've been trying to explain to you, so believe what you want, install whatever parts you want, just understand what something is or what it does. It is not a magical valvebody change, the only thing the servo does is apply the 2-4 band and which one you install changes how much pressure goes onto that band.

By the way, yes I have installed several, one being on my old '91 Camaro.

Ron U.S.M.C.

I’m not trying to argue the point all I’m saying is that the way my car shifts is different than before the servo swap. There must be many others that are reading this post that could reply with what there experience is concerning the way the servo has affected their car..But other than that I will leave this thread alone.

86_Dan_Z28

iTrader: (1)

Sorry to correct you,
The only thing the corvette servo does is apply the "2" band. If you want more holding power for the "4" band you need a billet 4th servo.

82tarecaro

iTrader: (4)

Years ago I installed a billet servo in a 700r4 I had at the time. I believe the install also involved removing one of the springs and also replacing another with a firmer spring. But that thing shifted hard into second after the install. The size of the servo affects the holding pressure, but the springs affect how fast the shift occurs.

rusty vango

I just had my 700-r-4 rebuilt .and the only mod from stock was the "corvette servo" I notice I have a stronger 2nd gear application as well as a firmer OD. it was worth it.

87zjeff

iTrader: (4)

Dan, the band is called the 2-4 band..he is correct in what he said.

paulo57509

FWIW, here's another installation variation.



Note the coil spacer on top of the steel cover, and the blue and black spring that fits inside of the existing cushion spring that sits under the 2nd apply piston.

These were the instructions that came with my Pro-Built HD rebuild kit for a 4L60E which also included a modified shift kit.

That three spring/coil spacer stack makes it harder than Chinese arithmetic to compress the steel cover (for snap ring install).