Hi guys, I have a low mileage reman 1986 model year 700R4 behind a very strong roller 327 w/ Holley stealth ram. I took the trans apart when I got it and replaced the separator plate w/ a new aftermarket one, and I also installed the Superior shift kit , a 3/4 WOT shift valve, 0.500" boost valve, and stiffer pressure regulator spring. I have additionally reprogrammed the governor using a superior gov. kit, to get 6200 WOT shifts. Finally, I added Corvette piston and accumulators when I had the trans apart. I used the longest servo pin available, to get 0.095" cover travel. I have a PATC Raptor 5X 2800 stall 9.5" lockup converter and 3.73 gears w/ 27" tires.

The transmission was flaring the shifts when I got it, before all the rework. It now shifts properly, and positively, but the shifts are not as crisp as I'd like. I don't want crash bang laying down rubber at 1/4 throttle shifts at all. I only want a firm shift above 1/2 throttle. Adding the 9.5" converter made the shifts noticeably softer than when I was running a tight 1700 rpm stock converter. W/ the current mods and the stock converter, I would get minor tire chirp 1-2 at WOT. Now w/ the 9.5" converter, there is no tire chirp and the shift is fine but I want it to be snappier.

The superior kit included a lot of springs that had to be changed, including accumulator springs. I guess the Superior kit helps but is not an all out performance kit?

What kills me, is I have an unknown year 700R4 in my other car, behind a beat 305 LG4, that shifts nice and smooth at low throttle, but above 1/2 throttle gives a nice tire chirp, without being harsh at all. I paid $40 for that 700R4 and it shifts like a million bucks. At WOT it lays down a little rubber 1-2, with the 140 hp piece of crap 305. I have no idea what shift kit is in that 700R4 but I want that same feel in the 700R4 in question.

What kit/additional mod's would you recommend? Like I said, I do NOT want harsh crash bang shifts.

 

a higher stall will tend to lessen the shift firmness at lower rpms.
saying corvette piston, I assume you mean servo.

- are your partial throttle shift points(rpm) correct?
- any idea how much line pressure you have?
- what color accum springs?
- does it have the aux. valvebody?
- any idea what the clutch pack tolerances are/were set to?

 

No aux valve body, its an 86 model year. It's a "rebuilt for GM" trans so I didn't set the clutches up.

Yes part throttle shift points are fine. Actually if anything they are on the high side, indicating more than enough line pressure.

The accum springs are red/pink now I think. They are whatever superior provided, and it was significantly beefier than stock

Yes corvette servo

 

hummm.
Other than the servo(I like billet for non-stock rebuilds), that's what I use. Never had one that didn't shift well, quick and precise all the time, progressively firmer the harder you step on it. In fact, I've got one in a street rod right now that I'm trying to get the 2-3 shift to lighten up a bit. - The only questionable item would be the clutches used and their tolerance.

I'd give a call to PATC and see what they think.

 

It shifts fine and it definitely has firmer than stock shifts, but not firm enough for me. I will most likely get another trans to rebuild from scratch, and transfer the parts over from the one in the car when I get that far.

Or just steal my brothers tire chirping 700R4 and stick mine in its place, he won't know the difference

Steve