Corvette Servo Debate

Pete94Silverado · May 2, 2009

After researching the Corvette servo mod, I can't figure out why there is any sort of debate on NOT doing this mod. I have read opposition to it that transmission shops say it will kill the transmission. In my feeble mind, I cannot figure out why it would kill the 4L60E in the truck but not in the F-body. I would suspect that...like the 10 bolt rear end...the 4L60E is a "corporate" transmission. Because of that, I highly doubt that the internals in the truck variation are any different than those in the F-body. In fact, if anything, I would think those in the truck are a more heavy-duty variety than the f-body. Even with the tow/haul option, I still can't see how that's any different than firming up the line pressure in the f-body.

So...does that make any sense? How could the Corvette servo break a truck 4L60E transmission? I have pretty much made up my mind that I am going to do this mod so...the outcome of this discussion really doesn't have any bearing for me...but...maybe for others???

-Pete

04Silverado

bigredmariner · May 2, 2009

Do it Pete.

svensk · May 2, 2009

After researching the Corvette servo mod, I can't figure out why there is any sort of debate on NOT doing this mod. I have read opposition to it that transmission shops say it will kill the transmission. In my feeble mind, I cannot figure out why it would kill the 4L60E in the truck but not in the F-body. I would suspect that...like the 10 bolt rear end...the 4L60E is a "corporate" transmission. Because of that, I highly doubt that the internals in the truck variation are any different than those in the F-body. In fact, if anything, I would think those in the truck are a more heavy-duty variety than the f-body. Even with the tow/haul option, I still can't see how that's any different than firming up the line pressure in the f-body.

So...does that make any sense? How could the Corvette servo break a truck 4L60E transmission? I have pretty much made up my mind that I am going to do this mod so...the outcome of this discussion really doesn't have any bearing for me...but...maybe for others???

-Pete

04Silverado

The 4l60e/65e maybe weak, but the 10 bolt "truck" rear end is not weak.

I agree, the mod should prolong the life of the transmission if anything. Most shops who recommend against it do so because they do not think you will be getting the PCM or TCM reprogrammed to adjust for the servo.

VMax2007 · May 2, 2009

The 4l60e/65e maybe weak, but the 10 bolt "truck" rear end is not weak.
I agree, the mod should prolong the life of the transmission if anything. Most shops who recommend against it do so because they do not think you will be getting the PCM or TCM reprogrammed to adjust for the servo.

All 4 of the shops that I talked to that recommended not doing it knew I had a custom tune and that I would adjust the shift pressure accordingly.

This is still a mystery to me. But one that I don't lose sleep over because I love how my trans shifts just the way it is.

Pete94Silverado · May 3, 2009

The 4l60e/65e maybe weak, but the 10 bolt "truck" rear end is not weak.
I agree, the mod should prolong the life of the transmission if anything. Most shops who recommend against it do so because they do not think you will be getting the PCM or TCM reprogrammed to adjust for the servo.

So the 10 bolt that is found in the truck is different from that found in the f-body and a ton of RWD GM vehicles? If so...did not realize that and I know that if you have a 6 speed (which I do in my SS) the 10 bolt is pretty much crap. With an auto at least it will survive hard launches but...with the 6 speed, you can pretty much count on grenading it with any sort of horsepower and sticky tires. In fact, mine is leaking pretty bad now and I'm on my second pinion bearing. So I can only imagine how the gears must look.

-Pete

04Silverado

svensk · May 3, 2009

The 4l60e/65e maybe weak, but the 10 bolt "truck" rear end is not weak.
I agree, the mod should prolong the life of the transmission if anything. Most shops who recommend against it do so because they do not think you will be getting the PCM or TCM reprogrammed to adjust for the servo.

So the 10 bolt that is found in the truck is different from that found in the f-body and a ton of RWD GM vehicles? If so...did not realize that and I know that if you have a 6 speed (which I do in my SS) the 10 bolt is pretty much crap. With an auto at least it will survive hard launches but...with the 6 speed, you can pretty much count on grenading it with any sort of horsepower and sticky tires. In fact, mine is leaking pretty bad now and I'm on my second pinion bearing. So I can only imagine how the gears must look.

-Pete

04Silverado

In the truck rear end the only thing that tends to grenade under heavy power is the G80 if you have one.

Ryan00TJ · May 3, 2009

Fbody's have the 7.5" ring gear 10 bolt with 27 spline axle shafts. 10 bolt GM trucks are a larger 8.5" 30spline setup. Much stronger than the Fbody 10 bolt.

My SS had the 7.5 and my truck's 8.5" RG is way way stronger. I never did break the 10 bolt in the SS though. Even with 420rwhp @ Nitto 555R drag radials. Broke the T56 once though.

Pete94Silverado · May 3, 2009

Fbody's have the 7.5" ring gear 10 bolt with 27 spline axle shafts. 10 bolt GM trucks are a larger 8.5" 30spline setup. Much stronger than the Fbody 10 bolt.

My SS had the 7.5 and my truck's 8.5" RG is way way stronger. I never did break the 10 bolt in the SS though. Even with 420rwhp @ Nitto 555R drag radials. Broke the T56 once though.

I wonder why f-body folks don't see this as a viable upgrade? I mean...most of the ones I know have gone 12 bolt or Dana 60. Seems like the truck rear would be an affordable upgrade.

420 rwhp and never grenaded the rear running Nittos...that's surprising...even more surprising is the T-56 problem. Usually, it's the opposite.

LawmanSS · May 3, 2009

I was debating this mod until I had lunch with Justin today...the debate is over, I'm going to do it.

VMax2007 · May 3, 2009

I was debating this mod until I had lunch with Justin today...the debate is over, I'm going to do it.

Will he need to tweak your tune afterward?

LawmanSS · May 3, 2009

He said it may or may not need tweaked...he said it really varies from truck to truck.

VMax2007 · May 3, 2009

He said it may or may not need tweaked...he said it really varies from truck to truck.

How firm are your shifts right now?

LawmanSS · May 3, 2009

Fairly firm...definitely not neck-snapping, but firm. It's really a night/day difference over stock. Basically, what Justin said was that the servo firms up the shift ever tighter than his tweaks, but it uses less line pressure to accomplish it. Therefore, he said it's better for the transmission. At least that's how I understood it...maybe Jeff or Rich can chime in with anything I missed from the conversation.

VMax2007 · May 3, 2009

Fairly firm...definitely not neck-snapping, but firm. It's really a night/day difference over stock. Basically, what Justin said was that the servo firms up the shift ever tighter than his tweaks, but it uses less line pressure to accomplish it. Therefore, he said it's better for the transmission. At least that's how I understood it...maybe Jeff or Rich can chime in with anything I missed from the conversation.

That makes sense since the Vette Servo has more diaphragm area. But with my shifts as firm as they are now, I wouldn't want them any firmer. So I guess I don't see the point (for my truck). Yes, he said it would improve my WOT 1-2 shift. But right now my normal shifts are perfect, in fact the first couple of cold-start, light throttle 1-2 shifts are even a bit harsh. But after that, they are perfect.

That's why I am hesitant to mess with it.

Justin??? care to chime in here?

Mark_in_Tulsa · May 3, 2009

Yeah I would really like to do this as well. But with my tune I had the every day shifts firmed up a little, but the tow/Haul shifts are really firm. Is this going to be over kill?

Putting comfort aside, will it be bad for the tranny with line pressure up and the Corvett Servo?