I just purchased a 99 GS400, I took it to one of are local drag strips, i went 9.21 @ 80 mph last weekend. I just ordered a set of 17 inch track lite rims which weigh 17.5 lbs. The Konig rims that are on the car now are 25 lbs. I just did a muffler delete, removed spare tire, I'm real hopeful that removing 36 lbs rolling weight will help the old GS400. I noticed that the factory shift comes at 6100 rpm right when the motor starts pulling. Has anyone found a way to change the shift perimeters on the 1999 GS 400? If so please help me out. Car is completely stock and unmolested other that what I just s
did with the muffler delete, I'm waiting on the track lite rims to come now. Thank you all .

 

As far as I know and my research took me when doing my build, there is no changes that can be made for shift points and pressures through tuning. It is just not equipped with a programmable TCM. I can't do it even with an AEM Infinity stand alone ECU. I've heard one can buy a dedicated TCM and have it ran with a stand alone ECM. But I think you would need a real expert and it would cos't a grip of money for the computers, dedicated sensors, and tuning etc. All to get the old auto trans shifting decently. Would be better off planning a manual swap if you think the things going to be a dragster. At some point you will overcome the transmissions capabilities as you chase power and ETs at the drag strip.

 

Thank you for your reply, I appreciate it. I took my 99 GS 400 to a local Drag strip and took it 9.20 s in the 1/8 of a mile. Bone stock here in South Carolina. I enjoy it. I had a 99 corvette which I used a hand held programmer and change the shift points from 6400 to 7400, along with a black wing air filter , picked it up 5 tenths in the 1/8 th of a mile.

 

Try putting the car in M mode and manually shift using the back buttons on the steering. Should be able take it all the way to redline.

Also thats a good pass for a stock gs400. 80 miles in the 1/8th is good for a 100-102 mph 1/4 mile trap. Do you have a picture of the time slip?
My full bolt on gs430 did 8.8 @80 and 13.7 @101

 

I wasn't surprised that it went 9.21. This is my 2cd
99 GS l400. My 1st. I bought back in 2005 had only 70k.on it. It had a new set of enki racing rims and new Dunlop tires . I sold it and 2009 with a hundred 150k l and regretted selling it. Anyway, I took it 9.07 83 mpg at Dorchester Dragway Charleston South Carolina back in 05 The one I have now is identical except 190k. So I was thinking about bolt on',s that are worth the money. Weather permitted, I'm going to take it to Carlina Drag way Thursday afternoon, it's a 1/4 mile track and make a few passes with it. I did shift it myself from 2cd, to 3rd , yet I only made 1 pass at orangeburg Dragway. The new owners call it ( South Carolina Motorplex). I was there to drive a 70 Nova back half car, 3000 lbs, on a 29 10.5 with a 588 big block, built for lots of NOS, 2 pro fogger system's , grudge car. . So I keep you posted on how my new old GS400 lol, runs. PS.
What the bolt on. Accessories helped the your car? Thank you.

 

You can modify the valve body for firmer shifts which will make it a little snappier. You can either shim the accumulators or shim behind the adjuster dial (search for "making the A650e hold power").

You can also drop in a GS300/Aristo diff which has a 3.73 gear ratio instead of the stock 3.27. That'll lower your overall gearing for faster launches, but if you're concerned with highway driving it'll raise your cruising RPM and hurt your MPG.

Also, consider doing motor/trans mounts, suspension bushings, firmer springs and dampers, etc. All those flexible points can add up to a noticeable amount of parasitic power loss if they're worn. If your chassis is shifting around under acceleration or braking, that's a lot of energy that's not making it to the wheels.

 

Thank you for your reply. Well said, freshen the old car up !


Car is in the Shade in these pics.

Ok

Bone stock.


Interior is nice, I'm enjoying it

I used original Exhaust tips with muffler delete. Sounds good, looks original.