What exactly does a shift kit do for an auto?

 

It increases pressure to the lines to make the trans shift quicker.

 

Thats not how the JMod works which is the best shift kit out there for autos.

Changing the shift pressure via a tuner increases line pressure which is bad for the tranny.

The JMod will make your shifts faster and harder. They also decrease wear on the tranny as a result.

 

i've heard good and bad about the JMod. Some people liked it, others regreted doing it (probably an installation mess up). You shouldn't let anyone do this unless you are 100% certain that they have done a few before. If it was me, I would get a converter, tranny cooler, dyno tune, and have your tuner adjust the line pressure a bit.

 

Here is a link to a JMod install:
http://www.dndgarage.net/jmod.htm

 

if you dont feel mechanically inclined than just remove your stock valve body sell that and buy a new aftermarket valve body that will take care of your hard shifting needs. this can all be done without having to increase line pressure. i used a tuner to increase the pressure and it didnt shift that much harder at all. increasing the pressure is going to lead to a premature pump failure.

i never did the J-mod because i just bought a whole new transmission. i dont have a problem with tackling a project like that just follow the instructions and you can find lots of info out there with pictures and part numbers for the things you need to complete this task.

my tranny has the Performance Automatic valve body and some consider it to have J-mod performance. shifts soft cruising and hard as hell at WOT. the overdrive shift sounds like small arms fire because it hits hard thats the only downside but im used to it and passengers are ask WTF is that.

 

You dont tune a car with a converter on the dyno. It should be on on the street and or at the track. That is my write up, it was the first time doing it. Very easy to do depending on the person.

 

Happen to have a ballpark figure of what that would cost without the dyno tune. The closest dyno to me is like 2 hours away, so I am waiting until summer to check it out. I dont know much at all about cars Im learning as I go and trying to check out this board as much as I can. I have few bolt ons but from searching the site I dont think it would be benifical to buy mods like tb/plenum, ud pullies, CAI's, etc... I just want to get my bang for my buck, and its been awhile since I have been able to spend any $$ on her. I have about 1k to spend and ive got the itch coming back.... lol thanks for the help guys.

 

800-900 for a good torque converter about 60 bucks for a much needed tranny cooler and another 50 or so for fluid and filter.

 

A shift kit does the same thing as the jmod, only the jmod was designed by the guy who designed the 4r70w tranny. Its a better way to do it. They both open up ports in the seporator plate which lets fluid flow faster and makes the tranny shift faster and have more pressure to hold the bands. I have done the J-mod and i have used transgo shift kits. They both worked well in my installs, but the J-mod is damn near free to do so it gets my vote. I would highly recomend doing a valve body mod and cooler as an auto cars first upgrades as heat kills trannys and this helps cut a lot out. Also a shift kit will drop you a tenth ruffly in the 1/4 mile with the faster and firmer shifts.

 

Think I would be better off getting this done instead of t/b & plenum. Looking for more torque/ throttle response, just dont know what will help. Right now my car shifts very hard with my SCT tune that I run, almost to the point where I dont like it some times. Car is pushing 100K and Im guessing the tranny is towards the end if its life.

 

Ok, so you already have some alterations done to the trans through your Xcal. I would leave it that way since you have so many miles on it. Once it takes a crap, get a rebuilt trans, which should include a better valvebody. Throttle body and plenum will give you a slightly better throttle response. Try to buy used.

 

Thanks for the help guys!