Finished J-mod on `04

ran260gt · Feb 15, 2009

Did the J-Mod to my Stang !

4R70W guys this mod was very easy , just take notes and take pics , makes things real easy , I did this with my car on jack stands in about 4 hours time over two days , started it yesterday before the sun went down and finish it today !

99-04 4R70W`s its really easy , drop the pan and valve body remove two springs and drill out 6 holes , there is some info on how to do it on the 99-04 4R70W on the web , I followed a wright up called (J-mod udates) on Mercury Marauder .net .

On the test drive at normal speeds it almost feels just like it did , but you can tell its shifting faster , then I gave it all the gas pedal , and it shifts very fast and the tire bark and the tail kicks to the side alot more then it used to

This is the best Free Mod ever

First pic is the Valvebody ready to be put back together and go back in , second pic is the open valvebody , what ever you do DO NOT turn it over in this state , Little tiny balls will fallout and your F#*% ed, Good luck

02nightmaregt · Feb 15, 2009

Cool dude, free mods are always the best

MaxedGT · Feb 16, 2009

The J-mod works great. Good job. Don't make the same mistake I made, and use a tuner to boost the pressures. I lost almost 3 tenths and about 2 mph in the quarter. Took me 2 years to figure out what was wrong. Leave the pressures stock with j-mod.

ran260gt · Feb 16, 2009

MaxedGT said:
The J-mod works great. Good job. Don't make the same mistake I made, and use a tuner to boost the pressures. I lost almost 3 tenths and about 2 mph in the quarter. Took me 2 years to figure out what was wrong. Leave the pressures stock with j-mod.

NO WAY , thats crazy because im getting my 4.10s and custom SCT X3 tuner done Friday , and thats just what I was going to do , Rise the Line Pressure , If this is true , than THANK YOU very much , because I would be so pissed if I ran slower times with my new mods !

How did you find this out ?

1badsilver99 · Feb 16, 2009

i really want to do this but im afraid of messing it up........ ive read alot about it and im really thinkin about it..... any other tips or pointers?

MaxedGT · Feb 16, 2009

I did the j-mod spring of 06 and installed an off road x-pipe at the same time. I left the shift pressures at stock settings to try it out before making any pressure adjustments. I was hoping to run 13.6. First run, 13.497@102.99 mph. I was blown away. That was the best run that day. Can't remember all the runs, but 13.6 was the worst I ran that day. it was especially sweet because I was running against an 03 Mach with more bolt ons than me and killed him. It was several weeks before I could make it back to the track. I upped the shift pressures a few weeks before going back to the track, and the weather was hot prestty well the hole rest of the season. Any ways After that I had trouble running even a 13.6. I figured it was the weather. with the pressures up, I could bark the ties on the 2-3 shift, both drag radials and e/t streets. So I figured that was great. Next season, wasn't running as well either. Figured something was wrong with car. I checked everything I could think of, but found nothing wrong. Last season I wasn't even trying anymore to run a new best. I took passengers for rides, even left my stock h-pipe on for a couple trips to the track. It still bugged me that I was running better and couldn't find anything wrong. So then I thought, what if the high shift pressures were putting a load on the engine through front pump, after all a power steering pump will put a load on the engine when the steerjng held against lock.
So I lowered the pressures and low and behold 13.5's no problem, even in hot weather. Ran a few 13.4's after that and a new best. With the shift presures up I trapped around 101 mph. With the shift pressures at stock I trap from 102 to 103.99 mph. I love my car again.

MaxedGT · Feb 16, 2009

By the way 260, I'm impressed with your times, with what mods you've listed. Nice!

ran260gt · Feb 17, 2009

MaxedGT said:
By the way 260, I'm impressed with your times, with what mods you've listed. Nice!

Thanks for the tips , like I said I would be so mad if my times got slower , and like you , who would know it could be something like line pressure that was holding you back !

And my times are the help of a track almost a sea level good prep and cold weather ! O and some weight reduction dont hurt

MaxedGT · Feb 17, 2009

Join here
http://forums.stangnet.com/groups/teh-auto-can-neva-lose.html
I posted some of my findings there. Us auto guys gotta stick together. j/k.

MaxedGT · Feb 17, 2009

1badsilver99 said:
i really want to do this but im afraid of messing it up........ ive read alot about it and im really thinkin about it..... any other tips or pointers?

Here's the instructions I followed. If you're mechanically inclined, and take your time you should be able to do it yourself. Watch out for checkballs and read the
instructions ahead of time. So you're familiar with what you're going to do. It's actually quit easy, but can be messy if your not carefull.
http://www.crownvic.net/tech/4R70Wnotes.pdf

ran260gt · Feb 17, 2009

MaxedGT said:
Join here
http://forums.stangnet.com/groups/teh-auto-can-neva-lose.html
I posted some of my findings there. Us auto guys gotta stick together. j/k.

I joined

MaxedGT · Feb 17, 2009

ran260gt said:
I joined

Mike97gt · Feb 19, 2009

MaxedGT said:
I did the j-mod spring of 06 and installed an off road x-pipe at the same time. I left the shift pressures at stock settings to try it out before making any pressure adjustments. I was hoping to run 13.6. First run, 13.497@102.99 mph. I was blown away. That was the best run that day. Can't remember all the runs, but 13.6 was the worst I ran that day. it was especially sweet because I was running against an 03 Mach with more bolt ons than me and killed him. It was several weeks before I could make it back to the track. I upped the shift pressures a few weeks before going back to the track, and the weather was hot prestty well the hole rest of the season. Any ways After that I had trouble running even a 13.6. I figured it was the weather. with the pressures up, I could bark the ties on the 2-3 shift, both drag radials and e/t streets. So I figured that was great. Next season, wasn't running as well either. Figured something was wrong with car. I checked everything I could think of, but found nothing wrong. Last season I wasn't even trying anymore to run a new best. I took passengers for rides, even left my stock h-pipe on for a couple trips to the track. It still bugged me that I was running better and couldn't find anything wrong. So then I thought, what if the high shift pressures were putting a load on the engine through front pump, after all a power steering pump will put a load on the engine when the steerjng held against lock.
So I lowered the pressures and low and behold 13.5's no problem, even in hot weather. Ran a few 13.4's after that and a new best. With the shift presures up I trapped around 101 mph. With the shift pressures at stock I trap from 102 to 103.99 mph. I love my car again.

the upped line pressure by itself did not cause you to run slower.. I bet something else is changed in that tune when you bump the pressures. or maybe the wheel spin from the firmer shifts?

I never had any of the mustangs I have done J-mods on or bumped the pressure on loose 2 MPH trap..

MaxedGT · Feb 19, 2009

svttech76 said:
the upped line pressure by itself did not cause you to run slower.. I bet something else is changed in that tune when you bump the pressures. or maybe the wheel spin from the firmer shifts?

I never had any of the mustangs I have done J-mods on or bumped the pressure on loose 2 MPH trap..

I was using a Superchips 1725 tuner up until August of last year. Switched to a Predater and used the 93 octane tune. My e/t's and trap speeds were about the same with both tuners, until I lowered the shift pressures back to stock. Most of the gains in E/t are in the first 330ft. It's not the weather either. We're talking almost 3 full seasons of racing. The car being an auto is very consistent, so we're not talking driver error either. Most of my runs are within .080 seconds in a night. I wouldn't have thought shift pressures could make that much difference either and that's why I took so long to try lowering them. I don't blame you for being sceptical, I'd be too if I hadn't found it myself. But I'm totally convinced.

txstang84 · Jan 5, 2010

Hey guys n' gals, I haven't been on stangnet for quite a while now. My wife picked up an '04 Black GT vert with an auto, and I was told by two friends of mine to get the j mod...only problem is all my searches all lead nowhere. Is this kit no longer available? Am I looking in the wrong place?

I really like the car and very much enjoy driving it, but, like many Ford automatics I've driven in the past, it feels like a slushbox...leaves much to be desired.

MaxedGT · Jan 5, 2010

Click on the link above that I posted. Best simplified instructions that I could find. Later models like yours don't need as many modifications as earlier models because some of the changes were already made by Ford. It's not a kit. Just modifications made to the valve body and accumulators.

txstang84 · Jan 6, 2010

Hey thanks man...much appreciated.

So, there's no parts that need to be installed, like stiffer springs and what-have-you? My knowledge of automatics is somewhat limited, but I've helped friends in the past install kits that had new springs in them.

navarro98gt · Jan 6, 2010

Nice work. Time for a higher stall torque converter!!

MaxedGT · Jan 7, 2010

txstang84 said:
Hey thanks man...much appreciated.

So, there's no parts that need to be installed, like stiffer springs and what-have-you? My knowledge of automatics is somewhat limited, but I've helped friends in the past install kits that had new springs in them.

No kit required. Just follow those instructions. You just enlarge a few holes in the separator plate, remove a couple springs in the accumulators.
The J-mod is a procedure developed by one of the engineers responsible for the design of the transmission. It works well and will not cause damage as some shift kits can.

Finished J-mod on `04

ran260gt

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