Who knows transmissions?

[68Stepbed]

OK, I have a carbureted LS1 with a 92 4L60(non-electronic) transmission. The trans has been built with upgraded internals, 2800 stall, and I believe a Trans-Go(whatever the builder ordered) shift kit. It's been in the truck for over 4 years with no major issues. It always wanted to shift early, but was easily fixed by changing weights and springs in the governor. I've been overall patient with it, but now that I'm taking autocross a bit more serious, I'd like to step it up some.

First off, the "kickdown" or downshift under throttle. Many times while driving at certain speeds, the trans just won't kickdown low enough and work well with the engine's powerband. The throttle valve cable is adjusted correctly, even if a bit too tight. To get the trans to kickdown more, do I need to start looking at valvebody adjustments? I had a builder once mention a reverse boost valve. What exactly does it do? Would it help? Is there somewhere else I need to modify or adjust?

Secondly, Many times when driving back roads, I'll put the trans in 3rd instead of OD. Upon doing this, the trans will downshift from 3rd to 2nd on it's own during deceleration into a curve causing engine braking. It's really nice and puts the engine in a comfortable rpm range to quickly accelerate through and out of the curve. However, when I'm autocrossing, I usually have to run in 2nd gear because most courses I run lately have been longer with decent speeds. The problem in this, is the engine won't downshift into first on it's own when decelerating and braking into a corner and the engine has to lug it's way out of a low speed corner in 2nd. Is there any way to get it to downshift itself upon deceleration? Keep in mind, I don't want it to do a hard kickdown style downshift under heavy throttle as this would probably cause the rear tires to break traction or upset the truck's balance and cause other issues. I'd rather it downshift upon entering the curve, not coming out.

Does any of that make any sense? Something I may do in the future is install a floor mounted shifter and manually manipulate the gears, especially if I can't get these issues sorted out first.

[mongocanfly]

Clinebarger...he would be the man...

[Blue Rat]

Originally Posted by mongocanfly

Clinebarger...he would be the man...

Yeap.

[Marv D]

PM sent to Sir Clinebarger,, he should be popping in sometime

I 'used to know' transmissions way back when GM had only 5 automatics in their arsenal ,, and NONE of them were electronic!! So My best help is pointing the real expert towards this post.

[clinebarger]

Originally Posted by 68Stepbed

OK, I have a carbureted LS1 with a 92 4L60(non-electronic) transmission. The trans has been built with upgraded internals, 2800 stall, and I believe a Trans-Go(whatever the builder ordered) shift kit. It's been in the truck for over 4 years with no major issues. It always wanted to shift early, but was easily fixed by changing weights and springs in the governor. I've been overall patient with it, but now that I'm taking autocross a bit more serious, I'd like to step it up some.

First off, the "kickdown" or downshift under throttle. Many times while driving at certain speeds, the trans just won't kickdown low enough and work well with the engine's powerband. The throttle valve cable is adjusted correctly, even if a bit too tight. To get the trans to kickdown more, do I need to start looking at valvebody adjustments? I had a builder once mention a reverse boost valve. What exactly does it do? Would it help? Is there somewhere else I need to modify or adjust?

Secondly, Many times when driving back roads, I'll put the trans in 3rd instead of OD. Upon doing this, the trans will downshift from 3rd to 2nd on it's own during deceleration into a curve causing engine braking. It's really nice and puts the engine in a comfortable rpm range to quickly accelerate through and out of the curve. However, when I'm autocrossing, I usually have to run in 2nd gear because most courses I run lately have been longer with decent speeds. The problem in this, is the engine won't downshift into first on it's own when decelerating and braking into a corner and the engine has to lug it's way out of a low speed corner in 2nd. Is there any way to get it to downshift itself upon deceleration? Keep in mind, I don't want it to do a hard kickdown style downshift under heavy throttle as this would probably cause the rear tires to break traction or upset the truck's balance and cause other issues. I'd rather it downshift upon entering the curve, not coming out.

Does any of that make any sense? Something I may do in the future is install a floor mounted shifter and manually manipulate the gears, especially if I can't get these issues sorted out first.

Rarely do we see such a well written question!

When you put a 700R4/4L60 in manual 3rd/D3, The Overrun Clutch comes "On" giving engine braking, The Overrun Feed can be blocked, But I don't recommend it as the Overruns help the Forward Sprag stay alive. IF it is falling out of 3rd into 2nd at speeds above 10 MPH upon deceleration...............Your Governor calibration is really wacky

The Intermediate/Reverse Boost valve boost pressure in Reverse, & Manual D1/D2, A Larger Ratio boost valve will just increase Line Pressure in those 3 Ranges, Does not effect shift timing at all.

We can dive into the hydraulics if you want. But, Your never going to get automatic downshifts at speed with minimum TV Pressure.

[68Stepbed]

Originally Posted by clinebarger

Rarely do we see such a well written question!

When you put a 700R4/4L60 in manual 3rd/D3, The Overrun Clutch comes "On" giving engine braking, The Overrun Feed can be blocked, But I don't recommend it as the Overruns help the Forward Sprag stay alive. IF it is falling out of 3rd into 2nd at speeds above 10 MPH upon deceleration...............Your Governor calibration is really wacky

The Intermediate/Reverse Boost valve boost pressure in Reverse, & Manual D1/D2, A Larger Ratio boost valve will just increase Line Pressure in those 3 Ranges, Does not effect shift timing at all.

We can dive into the hydraulics if you want. But, Your never going to get automatic downshifts at speed with minimum TV Pressure.

OK, so basically, I just need to look into getting a floor shifter and working the trans manually, right? Will downshifting like this cause other issues? As for engine braking, I like it, so I have no desire to bypass it. I'm not exactly sure what size the current boost valve is, but it does great in D1 and D2, so I see no reason to change it since it only increases line pressure. However, my 2-3 and 3-4 shifts tend to be sluggish and early, and the detent or kickdown at certain speeds seems to be hesitant and/or non-exsistent depending on speed and rpm. It's never seems to want to drop to a low enough gear.

As for the governor, the trans was originally in a 92 C1500 pickup. The valve body was replaced with a rebuilt unit from a Camaro. After first being built, it always wanted to shift way too early, no matter how the TV cable was adjusted. I talked to a guy to get a second opinion. He recommended getting a spring & weight kit and experiment with the governor. I tried a couple different weights that held it too far. I ended up putting the stock weights back on with only a heavier spring change. I don't remember the exact color of the spring. It does shift late under normal driving, but it's only an issue going into 4th as I have to be doing at least 48-50 with almost no throttle.(no TV pressure) I noticed a couple transmission parts dealer sell "Vette" governors setup to operate at 6500 rpm. Would this be a good option?

In some ways, I hate to even mess with anything. I've had it in the truck for about 4 years. It's been driven hard and beat on every time I get in it. I took it to the builder to have it serviced(yes, long overdue.) As the fluid drained, it was clear, first good sign, then he dropped the pan. Absolutely no metal or even clutch material around the magnet. He said, "I must've done something right." I was shocked, seeing that I've not treated it well.

[GMR-PERFORMANCE]

If you don't mind why did you choose not to use a US shift module?? I run a 4l80E 4200 stall 245/265 ufo convertor with lock up and a D3 trans brake and run it at the track and on the street and have to say that it is amazing how well it works. The Newest US shift module will now learn ( to alter shift points based on driving and TPS) and offers data recording as well .

[68Stepbed]

Originally Posted by GMR-PERFORMANCE

If you don't mind why did you choose not to use a US shift module?? I run a 4l80E 4200 stall 245/265 ufo convertor with lock up and a D3 trans brake and run it at the track and on the street and have to say that it is amazing how well it works. The Newest US shift module will now learn ( to alter shift points based on driving and TPS) and offers data recording as well .

My trans is a non-electronic 4L60, basically a renamed 700R4.