4R70W shifts too fast after gear swap please help

Mustang_Guy81 · Dec 15, 2011

Ok let me say ive been reading here a while before joining and lots of great info!!!

The car in question here is a 1996 mustang gt with a 4R70W tranny and the following mods

VORTECH V1 supercharger 7lbs
UPR X pipe
Flow master cat back
K&N filter
Subframe connectors
BBK 78mm TB
2in drop
4.30 rear gears
17x9 cobra r up front
17x10.5 cobra r rears
Upgraded slotted/cross drilled rotors
Dallas mustangs speedcal
superchips 1725 tuner

As you can see just a descent daily driver for warm weather.

The issues im having are at part throttle and i mean very light throttle the car wants to shift into OD by about 30-35mph.But if you nail it from say a dead stop it will flat out and get and holds the gears like it should.This only started after the gear swap so i had a tuner that came with the car the superchips 1725 max micro tuner and i set the shift points/line pressure to max and set the gear ratio to 4.30.That did almost nothing so i searched online and seen others had used a dallas mustangs speedcal so i bought one and this thing actually worked and got my speedo dead on with my gps units i tried two to make sure but it still shifts too soon whats the deal?

If i kinda gas it a little off the line she shifts normal and seems just fine same as if i mash it WOT it will hold the gears and do as it should also cruising down the road if i nail it wot itll downshift as it should only at light part throttle do i have issues.Is this just the nature of the beast or am i missing somethin?

Deleted member 38176 · Dec 15, 2011

Wow, a blower AND 4.30's on a 2V? Thats probably the worst combo to ever have. 3.73's are max for a blown 2V. That aside, I want to say that the problem lies in your tune/tuner. From my understanding, you're setting your parameters by yourself and unless you know EXACTLY what you're doing, you should leave the programming to the experts.

Im going to go ahead and say that with tranny issues aside, that car will most likely not perform to the best of its abilities with that blower/gear combo.

nyuk98gt · Dec 15, 2011

Mustang_Guy81:

Welcome to StangNet!

You've got yourself a nice Mustang. Good work.

Our cars (pre-99's) do not have electronic speedos so we have to use a SpeedCal or a plastic gear (not a great option, imho). So far, so good.

Head over to TCCoA.com and find "Transmissions 101" by J. Wroblewski, former Ford transmission engineer and tuning guru. It is a series of articles in the Tech Articles/Transmissions section and tells you about all you need to know about the 4R70W.

The engine speed is now rising at a faster rate with the new rear gears. The shift points must be lowered so that the actual shift occurs when wanted/needed. Shift points can be MPH based or RPM based (your choice). You will need to work with your tuner so he can adjust your tune or you can get SCT's ProRacer software and do most of your tuning by yourself.

Transmissions 101 contains the J-mod, the best thing you can do for your 4R70W, imho. It will quicken the shifts without making them harsh. Quicker shifts mean less friction so less heat and destruction of the materials in your trans. Git 'er done.

Last thing, the 3-4 shift at WOT is never to be done. You'll burn the OD band and then it has to be replaced. Your engine is producing a lot more torque so it is essential that you avoid 3-4 WOT shifts. The tune can prevent this, too.

HTH,

Chris

Mustang_Guy81 · Dec 15, 2011

Well thats the thing i dont have a shop local to tune it.The closest is anderson in clinton and ive talked to danny there many times but theyre prices are down right ridiculous!

Ive read the articles there on TCCOA.com but im not really a tranny guy.Is there any way to make this all work with what ive got now or do i need more software/tuning and all that?If so i may swap it all back over to the 3.08's since i bought a whole new rear end to put the gears in and then swap it over so down time was minimal and had plans to put the 3.08's and 8.8 T-lok in my 84 lx coupe.

Also why is 4.30's a blower and a 2v a bad combo?The car seems like it would be bad ass if it didnt spin constantly like on wet pavement lol drag radials are a must but not until it shifts properly.

Mustang_Guy81 · Dec 15, 2011

BTW thanks for the welcome a fast responses!You guys rock!

nyuk98gt · Dec 15, 2011

Mustang_Guy81:

You can get a modified valve body from Darren at BC-Automotive.com. You can do the J-mod yourself - I did and I am not a tranny guy either. (This is the first auto I have owned.)

Yup, you'll need some suspension/chassis mods to make the most of those gears. But, it seems that you have a bead on that issue already.

Chris

Mustang_Guy81 · Dec 15, 2011

So ill need to go internal to get this thing to shift right?

Yea if so im good ill be putting the 3.08's back in!God i love my 5.0's i have 2 an 84 and an 89 and they dont have to have all this crap to run righ and when u do one mod it dont take 10 more to support that one you just did.

nyuk98gt · Dec 15, 2011

Mustang_Guy81:

LOL! Drop the pan, take off the electrical connectors, take out the 26 bolts, and head to the workbench. For your '96, you should upgrade the accumulator pistons (and springs). This might sound like a big job but it is not a big job. Take your time and you'll do just fine. Take pictures as you go so you remember what goes where. I had an '86 Capri RS way back when I was much younger and I did the J-mod to my '98 by myself. (Yes, I'll take the applause, thank you.) I think you can handle the J-mod with no trouble. Read the how-to articles by A-Train and you'll do fine.

You don't HAVE to do the J-mod but your transmission will be much happier with all that torque coming through it. The main thing that you need to do is adjust the shift points. (Nagging again: with quicker shifts by the J-mod, you can get the best shift points and be more consistent at the track.) So, let's leave the 4.30's in and get a tune and see how that goes. I bet you'll never not smile when behind the wheel.

Chris

usaf_branham · Dec 15, 2011

Nightfire said:
Wow, a blower AND 4.30's on a 2V? Thats probably the worst combo to ever have. 3.73's are max for a blown 2V.

I would disagree with that statement...

He has a vortech and a slushbox, personally the highest I would want to go is 4.10 with a blower. I had 4.10's in mine and switched them for 3.73's after about a year of driving with my blower. I regret it. I miss the 4.10's, they were alot more fun, and that is with a twin screw. I would think that 4.10 would be optimal for a centri.

Also, in reference to the trans. You are going to want to take it to a tuner to fix your shift points.

sneaky98gt · Dec 15, 2011

So wait, you are saying the only problem is that it's shifting into OD too soon? And by too soon, you mean 30-35 mph?

I honestly don't see the problem here. My 98 GT with stock 3.27 gears changes into OD at around 40 mph so long as I'm not on the throttle hard and loading the motor. My granddad's 01 GT with the stock 3.27s changes into OD even sooner, usually around 35. If you follow the math, that's at about 1500 rpm in 3rd gear; swap in 4:30s, and if it changes at 1500, that's only 27 mph. So you are actually shifting later than my granddad's 01 GT would if it had 4.30s in it.

FWIW, my transmission does a few funny things when I have the 3-4 shift pressure turned all the way up. So I just don't turn it all the way up.

And also, the J-Mod is really not hard at all. Especially considering you have a supercharged Mustang (as do I), I think it should be a REQUIREMENT. I promise that you will absolutely love it. And if you've done hardly any wrenching on your car at all, you can do the J-mod. It only took me a few hours from start to finish, and I had never touched the transmission before. Follow the write ups over on the TCCoA, and it's practically impossible to mess up.

1993cobra5.0 · Feb 6, 2016

Hey guys ,

I have a 96 gt 4.6 . If I put it in D . The car don't move . If I put it in 1 it stalls
In 2 it will go through all gear great if WOT . But shifts early if I drive it normal.

Any help would be great

Decipha · Feb 6, 2016

create a new thread

obviously your shifter is off

Rcdgl · Jun 21, 2020

If you changed your gears, the trans and engine/trans electronics are seeing the same rpm signal at a much lower road speed/mph and are still shifting when they are programmed at lower loads and engine speeds.
You did not say if you change the speedo or speed sensor driven gear, but you should start with changing that. It will get the signal at speeds closer to what the computer is expecting.
Also should be able to handle via software.

4R70W shifts too fast after gear swap please help

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