30th t/a

iTrader: (51)

I posted this before and because I thought it was slipping but Im not sure that I would call it slipping.

when on the dyno in 3rd gear, my tuner will bring it to 3200 and open it up, it will start to rev and Right at 4400rpm the motor will immedialty go to 6500. I really wouldnt call it slipping. Its kinda like accidently hitting neutral. However 2nd gear works fine on the dyno so he tuned my car in 2nd gear.

I just spoke to my transmission builder and he talked about how he drilled a hole in the valve body with a bracket over it and that was a safety feature and he is thinking on the dyno, the trans is seeing to much pressure causing this safety feature to come into play.....Any ideas?

3rd gear seems to work Ok on the street though. I havent raced it yet.

thanks
John

DevonsZ

iTrader: (20)

does ur tranny fluid smell burnt or is it low
also the dyno u run on does the nose of the car angle down, one of the guys i run around with said the pump might starve under a hard pull causing they tranny to slip

jakeshoe

iTrader: (14)

Your builder is talking about the Transgo pressure relief for torque signal oil that prevents them from cracking pistons and drums.

You need to go through the normal diagnostic procedures.

Fluid level?
Shifter adjustment?

Then you move on to a pressure check. You need to hook a gauge up to mainline pressure and try to get the symptoms to reappear.
If they do so, you need to see what happens to the pressures when this occurs.
Do they spike and then drop, just drop, or stay steady.

If this transmission isn't dual fed, you may be driving through the 3rd gear clutches.
I've seen some otherwise reputable builders who don't know or understand the dual feed mod used on a TH400 or 4L80E. When it's not done, at 500 HP the direct clutches are going away...

30th t/a

iTrader: (51)

thanks for the great info.

Going by the Lokar flexible dipstick, the fluid level is good. The shifter goes into each gear perfect, so no trouble there. Once I get my shocks back from getting rebuilt, Im going to take the car to him and he is going to pressure test it.

What is dual fed mean? Is there a way I can check my transmission to find out if it is dual fed? I was told the transmission came out of a 1994 van.

I wanted to add that this transmission is freshly built and I put about 300-400 EASY miles on the transmission and the 1st pull on the dyno it did this problem.

jakeshoe

iTrader: (14)

Just because the shifter goes into gear doesn't mean it's adjusted right.

How was the adjustment done?

I prefer to put the trans in 4th (or 3rd) and adjust the shifter so that the cable goes on without any bind or tension on the trans shifter lever.

Find out what your builder did for the valve body kit. Did he use the Transgo kit?
I'm assuming this car is setup for automatic function or is it full manual function?

All the Transgo kits use the pressure relief on the torque signal oil, including their regular SK.
I don't believe the SK dual feeds.

The HD2 and HD3(manual) kits do. So if it has a TransGo HD 2 or HD3 you should be good.

I prefer to do it differently but the fluid path on the TG kits is adequate IMO.

They've changed (simplified) the HD2 Kit somewhat recently.

jakeshoe

iTrader: (14)

Also,
If you do see a pressure drop, add a qt of oil and see if the problem goes away.... That will help diagnose the possibility of a fluid starvation issue.

30th t/a

iTrader: (51)

This Transmisson shifts automatically.

I believe I put the transmisson lever & shift idicator in neutral. then shifted it all the way to park, checked the lever and it was good then I shifted all the way back to 1st and it was good.

What do you think could be happening if the shifter isnt adjusted correctly?



As a test, I would cruise at about 70mph, kick it down and it would go all through 2nd and shift into 3rd and would pull fine and I would let off at 115 which is 5150 rpms and it did not "act" up on the highway like it does on the dyno at 4300rpm.

here is what his receipt says for parts:
34 element sprag
forged outer race
new bushing
high energy clutches
new filter
heavy duty snap ring for 2nd
new solenoids
Trango shift kit
High pressure releif valve
heavy duty spring, high clutch relief

Thanks!!

jakeshoe

iTrader: (14)

If he used the Transgo HD kits it includes the HD snap ring and hi-rate direct return springs.

I'm thinking he used the regular SK and you are driving through the directs with full load on the car.

You could up the line pressure using the PCM as a temporary solution but it sounds like your builder might need some help in the performance build department.


Get a pressure guage on it, don't go over 220 psi line at any point. 200 should be plenty on this unit if it's right.
If it slips with 200 psi, it needs to be correctly built.

30th t/a

iTrader: (51)

I got to find out if he used the SK or the HD kit.

Shouldnt the transmission do this on the street too? It doesnt and thats what confuses me.

jakeshoe

iTrader: (14)

You may not be loading it as hard on the street, the car is already moving so the torque required to accelerate it may not be as much as the dyno load.

30th t/a

iTrader: (51)

Good point.

cablebandit

iTrader: (37)

turbo cars on the dyno seem to almost never load as hard as on the street. Could you be spinning? A stock 4l80 should hold a 6-700hp car on a dyno. if its working on the street, i think the tranny is fine

jakeshoe

iTrader: (14)

A stock 4L80E would have real issues with 600-700 HP on the street or dyno. 3rd gear would usually slip with reasonable line pressure, it might hold if it was already in gear and not making the upshift to 3rd (as in a dyno run where it is put in third for the run) but a 2-3 upshift under load and the clutches would probably never completely engage at 700 HP.
There isn't enough apply area to hold, that's why knowledgeable builders fix this when they build the trans.

30th t/a

iTrader: (51)

Its done this on 2 different dynos.If this is considered slipping, then I never seen this kind of slipping before.

Is there somehting I could disconnect so that the transmission wont downshift into second on the street. Id like to have it at 3200 on the street and nail it without it downshifting.

jakeshoe

iTrader: (14)

Is the rpm where it begins to slip about when you get full boost?

30th t/a

iTrader: (51)

honestly Im not sure. We've even sprayed the rear tires down with VHT and it still did this. Like I said, 2nd gear worked fine. It only does this is 3rd gear.

jakeshoe

iTrader: (14)

3rd gear is the weakest gear in a stock 4L80E. The clutch apply area is too small, not much bigger than the apply area of a 4L60E.
The advantage of the 4L80E (besides stronger parts) is that this is easily modified for much greater apply area.
In stock form the 3rd gear clutches are going to slip with any real power (over 500 HP, dependent on line pressure, clutch material, etc).

If your builder doesn't know what he is doing, he will fail at this station, do not pass go, do not collect your $200, the 3rd gear clutches are going to give up the ghost in a few runs.

I've seen on this forum, supposedly expert builders, not aware of this.

On a 4L80E, 4th gear is also driving through the 3rd gear clutches, might see what happens when you put full load on it in 4th, it should show up in 4th too as a slip.

Do you get any slippage codes from the trans when it happens. The PCM should pick up the slippage if it's internal to the trans and not tuned out.

30th t/a

iTrader: (51)

I dont have any transmission codes being shown. I dont think my tuner saw any codes either.
For me to test 4th gear out I got to be going 140mph or else it will kick down. Thats why I wanted to know if I could unplug somehting to stop the transmission from shifting.

As far as the builder, I knows he's built some transmissions for a guy that comes on here thats runs 9s NA and he builds alot of transmissions for some of the fastest local guys in my area. But who knows.

jakeshoe

iTrader: (14)

You could tune a kickdown from 4th out of it pretty easily, or for testing purposes you could make it hold 4th with the tuning software.

hawkls7

I had the same issues with my 4l80e on the dyno. i would say that it is the converter. originally i had a smaller converter and when on full power in third gear pulls the stall would keep climbing up as well as the engine rpm. I then purchased a larger diameter convert which is now the yank 3400 for supercharged app and it has helped . but it is stalling on the dyno like 5000. we are seeing 1000rwhp. im not 100 % sure but it seems to be converter related