Hey guys,
I'm getting ready for another 700R4 and I wanted to know everyone's thoughts/opinions on this. I am considering a B&M Transgo shift improver kit, but I also kind of wanted to try a corvette servo. Is there a big disadvantage to having both and would having both really be better than just one? I mean they both essentially just firm up shifts right?( and the servo sort of acts like a 3rd gear accumulator? )I guess I wouldn't really want to lower my trans lifespan too much.

Thanks so much for your input!

Fred

 

I put the Corvette servo in mine first just to see how much of a diffrance it made.
Not only that I did not want to mess with a perfacty good transmission at the "kit" level.

The servo is all that was nessary. Shifts are nice and firm.
You can even feel them at part throtel .
When I hit "WOT" from a roll or off the line it will shift hard enough to bark the tires when it hits second gear and again in third.
Love it.


I do also have a gear replacement from 2.73 to 3.42 (that does make a difference)and an Eaton Posi unit. That's both tires barking.


Heres how to install it.
=
http://sethirdgen.org/servo.htm


I believe the servo should be tested first any way so you have a gage to work with if you install the shift kit. You will know exactly what improvement the kit actually makes. If you go with the kit or just buying the servo I highly recommend "Pro-Built Transmissions" on line.
= https://www.700r4l60e.com/

 

Hi Fred, I ran a B&M kit back in the day when I didn't know any better and they simply have you block the travel on the accumulator pistons. This results in a jarring 1-2 shift at all throttle positions which really sucks unless you are into impressing high school kids. I would instead go with a TransGo kit (which retains the accumulator functionality) and yes, it doesn't hurt to add a corvette servo as well. When you install the kit, don't go overboard when drilling the 1-2 feed hole in the separator plate. I believe with the vette servo, you can get by with a slightly larger hole simply because it takes a greater volume of fluid before the servo is fully pressurized due to the increased surface area of it compared to the stock servo. Once applied, of course it will clamp the band with greater force which never hurts.

Oh, and X2 for Pro-built. I highly recommend Dana and his parts/kits as well.

 

Thank you guys so much for responding, really value your opinions. Sounds like I could save a little $ and just install a corvette servo, but it also sounds like a Transgo kit on top of that wouldn't be a bad idea. Do both of these firm up 1-2 and 2-3 shifts, or does the kit just firm up the 1-2 mostly? Thanks for the warning by the way I'll try and stay away from the B&M transpak despite its tempting price. Has anyone tried both vs. just one? Not sure if it makes a reasonable difference for the money to install both.
Thanks again,
Fred

 

You're welcome, that's what this forum is for!
My brother installed a Transgo kit in his 4L60E and kept the stock servo. It was in a 4.3 Blazer so it had a small servo, the smaller stock one. We went aggressive on the 1-2 feed hole and there is a spring in the valve body you have a choice with as well for the 1-2 accumulator. Red or white if I remember right. I don't remember which one we used but I can say for certain it shifted very quick from 1-2. It was a little too aggressive actually.
From my experience, to firm up the 2-3 shift you have to remove the servo and install the stiffer servo spring included I the transgo kit. That spring serves as the 2-3 accumulator. The old B&M kit I first tried did nothing for the 2-3 shift at all. And in my opinion the 2-3 needs more help than the 1-2 in a totally stock transmission. Part of the 2-3 shift is also affected by the 3-4 clutch clearance, but of course this is not adjustable unless you are tearing the trans completely apart. Hope this helps. If it was me, I would throw the vette servo in at the same time. You will have it out anyways and for $20 you might as well throw it in.

 

I had the complete works at the time. TransGo shift kit, accumulator valve, corvette servo...etc.

The difference between that an a stock transmission is night and day. After it was all said and done the trans was butter smooth at light and part throttle shifts. Never jarring. But as throttle travel progressed the transmission just shifted faster and faster, but never harsher. It would shift so fast it would never bark the tires, just a sudden rush of acceleration.

Dana at Probuilt walked me through several steps of the install, as well as a few other tweaks not listed in the manual.