tpi88camaro

iTrader: (7)

First off, this transmission does not have a shift kit in it per se, but a superior shift correction kit installed along with their servos. When I built this, that is the one thing I did not want, was a harsh shifting transmission. Those days are behind me. The only way I can best describe my issue is it is like this was a purpose built race transmission. It hits that hard when going from park or neutral into reverse. My line pressures are all in the specified ranges for all gears and makes no difference if the tv cable is hooked up or not. I'm perfectly happy with the way it shifts going into the other gears. When I'm driving it, the part throttle shifts are nice and firm, but later than I want. I will correct that with a little governor tweaking.

I am wondering what is going on inside the transmission to make it shift like this going into reverse?

Is this something that can hopefully be tamed down so to speak without pulling the transmission. I would like that to be a last resort if at all possible. Though with my luck, that is what will need to happen. LOL

Thanks in advance for any input on this,

GeneralDisorder

iTrader: (1)

What's your idle speed?

91 1LE

iTrader: (1)

Check your engine and transmission mounts for wear and/or loose bolts.

tpi88camaro

iTrader: (7)

650 rpm

tpi88camaro

iTrader: (7)

They are new and tight.

paulo57509

I always though harsh reverse engagement was characteristic of a 700R4.

My old spiral bound notebook has a date and description that GM tried to address this issue in February 1987 (from a TSB or trade mag tech article?). I don't know what or how they address this.

GeneralDisorder

iTrader: (1)

Harsh engagement can potentially be caused by an 87 input housing being used on an 82 to 86 trans.....

The 87+ input housing has no forward clutch orifice....

This many years down the line though it's hard to say but it was enough of a concern that GM addressed this potential mix up in their educational literature from back in the 80's.

GD

Pro Built Automatics

Was the transmission rebuilt recently? The reason (most likely) for this is the reverse/input clutches coming on before the low/reverse apply. What year is this transmission?

tpi88camaro

iTrader: (7)

It has been rebuilt twice. The last time by myself. The case says it is a 91. After a lot of searching I had come to the conclusion that what you described is what is happening. Most likely the contributing factor being that the only reverse input drum I could find was one with the large square feed hole. Pump also has large square feed hole.

Pro Built Automatics

I use the late reverse/input drum in all of my builds and kits. This is fixed by running more clearance in the reverse/input clutch pack. There is one major difference in my reverse/input clutch packs, I eliminate the Bellville steel that chews up the drum and replace it with the waved steel from the 1982 - 1986 reverse/input setups. I use the thicker clutches from the 1982 - 1986 reverse/input setups also to keep the clutch clearance within spec. In the low/reverse clutch pack, I leave it alone at apx. .040" - .050" total clutch clearance. I use "turbulator" steels in both of these clutch setups. It is rare I get this complaint of a harsh reverse. Make sure you remove the checkball from the capsule that sits above the low/reverse passages in the rear of the case. This will apply the low/reverse clutches quicker.

tpi88camaro

iTrader: (7)

I used regular flat steels along with waved ones in the clutch packs. I set the clearances as close to the middle as I could and if it was going end up being either on the tighter side or loser side, I chose the loser side of things. I did put another checkball capsule in the case as the checkball had fallen out of the one that was in it. I will pull it out and see what effect it has. Would going back to the stock reverse boost valve make much of a difference?

Beginning in '93, what was the reasoning behind the added checkball in the VB and the small orifice in the spacer plate? Was that done for a slower engagement and quicker release of the reverse/input clutches after they went with the large feed hole in the reverse drum?

Pro Built Automatics

I have not looked at that closely as TransGo has said that you could leave that checkball out and since I never had a problem here (having built a few 1993's over the years), I never gave it any thought.

tpi88camaro

iTrader: (7)

Drove the car a bit more and come to the conclusion that the shift characteristics are not what I really want. I ordered a transgo sk 700 kit and a new spacer plate.

I pulled the VB out and found no checkball in the back of the case for lo/reverse. I compared the holes in the spacer plate that came out to transgo instructions. All the holes were considerably bigger than what transgo wants. Makes me wonder why I didn't buy transgo initially instead of superior.

I didn't mention it, but I am currently using a 12" converter. I know this will affect shift firmness. I know it made a huge difference when I went from a stock converter to a 3000 stall in my TH350.

I'll be back with my findings when I get it back together in the next day or so.

Pro Built Automatics

If you want to make this kit an Heavy Duty version, give me a call 909 785-1876.

tpi88camaro

iTrader: (7)

Found a '93 VB. Got the trans all back together. Reverse engagement is much better. Shifts are a little later than I want, but can work on the governor to fix that.

Now I have another issue that was probly there before, but didn't pick up on it. The 2-3 is not right. Best way I can describe it is it feels like 2nd is releasing too early before going into 3rd. Is this was a 2-3 cut loose is? What causes this and how to fix? Thanks.

RBob

iTrader: (1)

It is a timing issue. The band needs to be released as the 3/4 clutch pack is applied. Release the band too soon and you get the 2-3 shift flare. Don't release the band soon enough and the dreaded 2-3 shift bind occurs.

Juggling the 3/4 clutch pack clearance along with the 2nd servo is required to fix it.

RBob.

tpi88camaro

iTrader: (7)

Funny you should respond. After doing some more thinking and more research yesterday I came across a thread from way back in 2003 titled 2-3 shift clunk from rear. In it you described what you were experiencing with your transmission and what you did to fix the issue. This is the issue that I am having with mine. I swapped out my billet TCI servos for a corvette servo yesterday and am going to drop the the VB here in a little bit. I am going to compare the holes in my spacer plate to what you used to fix your trans. For comparison, I may put my stock spacer plate in to see what it does. I am however running a wide band in my trans and that may or may not play a role in the problem. I wouldn't think so, but i'm not expert. My 3-4 clutch pack clearance is around .045".

Pro Built Automatics

You need to get the hole sizes correct on the separator plate. What I recommend here will fix this as long as everything is as you say. The wide band does not change anything as far as release. The 3-4 clutch clearance is right in the middle of what I recommend for the 700R4 with the Corvette servo. As long as the separator plate is in good shape, you are fine. Let me know?

tpi88camaro

iTrader: (7)

Here are the holes sizes that I am using:

A: .093"
B: .076"
C: .105"
D: .125"
E: .125"
F: .075"

Car is back together and will test drive tomorrow. Hopefully the above hole sizes and swapping out the TCI servos for the corvette servos will make the improvements I need/want or get me real close.

Pro Built Automatics

3rd gear "A" = .110"
2nd gear "B" = .076"
3-2 "C" = .125"
"D" = .125"
4th gear "E" = .125"
Band release "F" = .093"
Remove the spring from the 3-2 downshift valve. Install valve and pin only. Makes for a much quicker 3-2 shift. If you want it faster still? 3-2 "C" = .157". These hole sizes are for using the Corvette servo and the 12" stock diameter torque converter. If you like a firmer 3rd gear, "A" = .125", otherwise .110" is fine here.

tpi88camaro

iTrader: (7)

Drove the car for a bit and I must say that I think the servo change made the biggest difference of all. There is still a little bit of the snap/bang during normal acceleration in that it is quick and not drawn out like before and a little noticeable if I manually shift from 2nd to 3rd at 3/4 throttle. Now, if i'm in 3rd and mash the throttle at 35-40 mph it kicks down to 2nd nicely and will run to about 50 mph and shift to 3rd. The 2-3 shift under detent is very crisp and to the point. No evidence at all of a snap/bang shift.

Had I not had it all back together, I would have tried your suggestions, Dana. But figured since it was already back together and fluid in it I got nothing to lose but to see what it does.

Is there anyway to improve the 3-4 shift feel? Just want it firm enough I can tell it went into gear as I don't have a tach at the moment. I'm not going to be making any WOT 3-4 shifts or anything.

What I wouldn't do for a lift right now. Crawling around on the ground is not like it was 20 yrs ago. It's a pain now. Too much like work and not as fun as it used to be. Oh well, it will be worth it when I get it where it needs to be.

tpi88camaro

iTrader: (7)

Well, I went with the suggested hole sizes above and still getting that dreaded 2-3 bind. Pulled the vb again and upped hole F to .104" and still have a 2-3 bind. Should I keep going up in hole size or will that even make a difference? I thought it would have cleared up by now. Or should I pull the trans and look for something wrong inside?

TIA

Pro Built Automatics

You can drill "F" to .110" - .116" when using the Corvette servo.

tpi88camaro

iTrader: (7)

I drilled hole F out to what ended up being .122. Made no difference. Transmission is out and on the floor. Going to start tearing it down tomorrow and see if I can tell WTF is up with it. It's got to be something simple that I overlooked when I put it together and whatever it is is really getting on my last nerve.

Pro Built Automatics

Let me know if you need anything. The .110" - .116" is what I use on all of my High Performance builds when using the Corvette servo. Heavy Duty builds, mostly .093". Very rarely have I had to change anything here, having used these specs thousands of times over the years. There have been a few times over the years that we had to go back in to see why it was not going according to plan. If my memory serves me correctly, the case ended up being the problem on at least three occasions. Changed the case, problem solved as everything thing else checked out. Never did find what it was exactly though....