Baynut

iTrader: (5)

Can anyone tell me the drivability of a of a full manual valve body in a 4l80e or 700r4.
I have an LS2 going in an 80 T/A and want to add a turbo. But let’s say I am leaving a stop light… just cruising and shift to 2nd gear light on the gas, will I get tire chirp or whiplash? I want this car to cruise the streets and take my daughter for ice cream.

So tell your experience and setup, what you would do differently.

slow67

iTrader: (2)

If you install a vacuum modulator, the pressure will go up and down directly in relation to engine vacuum. So, if you foot isn't in it, the pressure will be lower.

Baynut

iTrader: (5)

Is that part on the trans then? and where would you source the vacum?

Thanks.

Photochop

iTrader: (74)

Like slow67 suggested, install a vacuum modulator in the trans and it'll cut your line pressure at part throttle making the shifts not so firm. I have one in my manual valvebody 4L80 and it makes it much more friendly to drive on the street with the vacuum modulator, it really cuts the harshness of the 1-2 shift.
Honestly I love this setup. I had a '79 camaro ages ago (first hot rod I put together back in high school) and it had a couple different transmissions in it over a period of 5 years, and I was always manually shifting it for fun (even though the valvebody was a regular one). So even then I liked the idea of a manual valvebody, and now I have it in a newer car...funny how that works haha.
Really the only thing that takes any sort of practice or finesse I guess you could say is approaching a stop and accelerating again from a stopsign or a turn after slowing/stopping. You have to get used to downshifting from 3rd to 2nd to 1st pretty quickly. I tend to 'feel' the 3-2 shift more under decel when nearly stopped more than the 2-1 (similar to engine braking as you come to a stop before the complete stop - it tends to feel less smooth than a normal valvebody). I usually give the car a slight bit of gas on the 3-2 as I'm about to slow down toward the bottom of what would be 2nd gear range, and then the 2-1 shift is made when you're nearly stopped and it isnt as harsh feeling. But, at a red light you typically have enough time to come to a complete stop and bring the shifter back to first with no hurry so this isnt a concern. With the power a car makes with boost, you can really be in any gear (short of OD, and even then its not bad) and the car will get going fine because of the torque of the turbo/load on the motor, so upshifting isnt as big of a deal at all, you just control when it occurs.

slow67

iTrader: (2)

The reason you feel it (and don't from an auto VB in OD) is that when you manually downshift you bring on clutches and bands that prevent the one way roller clutches/sprags from over-running (they hold forward motion but not engine braking).

Photochop

iTrader: (74)

Cool, thanks for clarifying. Is there a better way to do this or am I correct in giving the 3-2 a little gas on the downshift to smooth the downshift when approaching a quick stop and go?

Baynut

iTrader: (5)

So then for now maybe what i'll do is put in a stock 4l80e with no electronics and manuel shift it that will work won't it?.... I did a search and didn't find what I was looking for but is a 4l80e from any year o.k. and how can I ident different years. You guys have helped alot thanks.

slow67

iTrader: (2)

Thats a good method (IMO). It should cut down the amount of wear that the intermediate band will see.

It won't shift manually without modification.

Baynut

iTrader: (5)

What would you do? All my optiond are about the same price. 4l80e, 700r4 and t56... Still playing with the idea of a t56 for some reason. Either way $2000 plus when all parts are added. Just trying to think out of the box.

slow67

iTrader: (2)

4L80 for me.....I was T56. 700R4 is the weakest of the above. With a good build, a 4L80E will hold ~750hp, with billet shafts, 1000-1200. With a 36 element sprag or spragless, who knows?

Rolemodel

Like mentioned above 4l80e with vacuum modulator as long as you are in vacuum it can shift relatively mild especially if the torque converter is unlocked. Step o it and it shifts pretty fast and violent sometimes. Especially if the torque converter is locked and your going wide open throttle. I like the feel of a manual valve body makes me feel like i am driving a manual yet witht eh launching abilities that kick ***.

PBA

It depends on how fast boost comes on. If it comes on late, then there is less harshness in the shifts. If it comes on early then the pump goes to full line pressure and the shifts will be firmer. This too depends on what torque converter and stall you are using. When you downshift it manually, you must always give it a little throttle to match the gear change "quickly". Or you can wait till you get to a complete stop then move the lever to first gear. I like using the vacuum modulator when the boost comes on late, but if it comes on early it is very hard on the front pump, and then I will figure out something else here. If you are going to leave the computer installed, then leave it automatic, unless you really want the "full manual" setup.

Baynut

iTrader: (5)

I am just trying to figure a way not to use the ecm for the trans... no tunners here and the ecm is for a 4l60e so a trans tune would be needed from what I understand.
I am making my own harness and I have kept all of the wires just in case.

sirhk100

Bump from the dead!

I'm finishing up a build that's got a fully converted non "E" 4l80e. I've read various threads about the TH400 which translates over to the 4L80e's going boom on 3-2 down shifts.

Now I know with a manual valve body you want to use your brakes for decel, not the transmission down shifting. But let's talk a scenario or two...

Say I'm on an open street (ignore common sense and safety of being stupid on the street for conversation/scenario)... Approaching a light, it turns red. Start my braking, down shift from 3-2. LIght is absurdly short and goes green. Can I flat punch it to the floor? From what I read, this is a possible setup for a case explosion but I can't get a true understanding of if it is or isn't.

Another question and I don't know how to translate this to street talk. In all honesty, this transmission is going in an offroad truck, LQ9 with a Culhane built 4L80 behind it. Say I'm on a BIG uphill, I"ve got it pinned in 3rd but don't have the power to pull 3rd gear on this climb. Can I stay on the gas and grab 2nd or do I need to let up to down shift it?

I've been a manual transmission guy my entire life, this is my first jump into a performance type of Auto trans and while I'm doing the offroad thing, some of the questions I have would crossover to street like the downshifting then punching it question where I've heard you can experience literally deadly case explosions.

Scatter shield will be in play here either way...

Thanks,
Khris

paperboy326

I talked with my buddy who is in the know about transmissions and we will pull the transmission and see if something is a miss in there. We pulled it apart before the swap everything looked good, but he did a few common failure points 3-4 band, and a 2nd gear Corvette servo everything else looked good go. But it's not hard to pull and double check stuff and we can hook up scanner to the Jeep and see if it's commanding 2nd gear or not when shifting.