Help with TCM Tune.

[WisconsinHick1]

I am a truck puller and I am wanting to have my truck start in 3rd gear and shift into 4th while Im in 4low T/H on. How does the TCM determine what table to look at I see there is one for low range and tow/haul but I don't see a table to 4low T/H. Would I just be adjusting the low range shifts?

Thanks for all the help guys!

[THEFERMANATOR]

From what I found, 4 low doesn't use the tow/haul feature, just the 4 low shift table. Also myself and many others have found that the 4 low and tow/haul tables are mismarked and backwards.

[WisconsinHick1]

So T/H is 4lo and 4lo is T/H?

[anarchydiesel]

never built a tune to leave in 3rd then shift to 4th, but If you set your 1-2, 2-3 upshift speeds to 0 for all modes then it should go to 3rd on the line and then shift to 4th going down the track. Set your 4-5 upshift speed to 150mph so that it does not go into OD. We usually leave in 2nd and shift to 3rd, but that is with a workstock/hotstreet truck.

[WisconsinHick1]

This is for a 2.6 truck that spins the RPMs in 3rd. I have a feeling I can hold 4th no problem.

[05chevy]

I always leave the 1st table (table A) alone for you can still drive around using 1st gear. Then I change the rest of the tables for when you hit t/h, 4h or 4lo it deletes 1st and 2nd if you want it to

[WisconsinHick1]

Well Im still having an issue with my truck going in to OD when in drive.

Can someone take a look and see if Im missing anything?

Eric_TCM_01.tun

[Big Mike]

Try changing all the tables (except the "normal" table) to what you want to accomplish, not just the hot and 4Lo patterns as the columns are sometimes mis-labeled in certain OS. They're mis-labeled for mine I know.

[WisconsinHick1]

Big Mike do you or does anyone know if T/H really change anything when the truck is in 4low?

[Big Mike]

As I understand it the 4Lo tables override any/all T/H tables for both shifting as well as TCC apply/release. So in 4Lo it's using the 4Lo tables regardless of whether T/H is also activated or not.