Tow/Haul mode...What does it really do?

[CHYKYNLIPS]

I have heard different answers for how the transmisson responds while in t/h and some contradict the other. I know it wont give a guy a second in a quarter or anything rediculous like that but for the average guy with the average truck like mine that just has the basic tuner and exhaust with a factory tranny, does it help to shift better at wot?

I was told t/h mode locks the tc in 3rd gear and up which should help the transmission not have the slipping feel each time it shifts and act like it is "searching" for the next gear which may lead to slightly faster acceleration...is that true? If not, what does the transmission do differently in t/h mode vs the standard mode? (btw, i know t/h doesent stand for "track/haul ass mode", lol.)

 

[Cougar281]

T/H locks the converter earlier and keeps it locked (It's basically locked from 2nd up), and changed the shift patterns to help keep the engine in the power band, as well as help with engine braking.

 

[Mike L.]

Tow Haul will extend the shift points ( shift a little later ) to help the truck gain momentom under load. It also locks the converter in second gear to help cool the transmission. It also drops 100 psi of pressure to the trans ( any time converter is applied pressure drops ) which is not good if you are running any kind of tune. Will it run faster in the 1/4 mile? That is questionable. The pressure problem can be defeated with a built trans.

 

[Darin13]

i have an 04 with a full transgo and it stays right at 3500 untill 4th theb it falls out and takes a while to climb

 

[x MadMAX DIESEL]

i have an 04 with a full transgo and it stays right at 3500 untill 4th theb it falls out and takes a while to climb

Thats called overdrive :thumb:

 

[duratothemax]

although keep in mind once you go WOT at any speed, the converter will lock, even in normal mode. THATS why you really dont run any faster in a WOT 1/4 mile run whether you are in tow/haul mode or normal mode...because the converter still locks up just the same early in 2nd gear,


So if you go WOT from a stop in non-tow/haul mode, the converter will still lock at ~25mph in 2nd gear and stay locked from then on up. At less than WOT in non-tow/haul mode, it wont lockup until ~50mph in 5th gear. At less than WOT in tow/haul mode, the converter locks in 2nd and stays locked from then on up regardless of throttle positon.

ben

 

[05' Ditry Duramax]

So obviously there is no "advantage" to running in T/H mode when drag racing?

 

[x MadMAX DIESEL]

It saves how you shift, so either use O/D or T/H for only WOT runs and the other for DD. That will help you the most, not allowing the trans to learn to "granny shift" when you need a balls to the wall shift.

I use O/D daily driving and T/H for killin ricers or when I feel diesel horny :rofl:

 

[CHYKYNLIPS]

It saves how you shift, so either use O/D or T/H for only WOT runs and the other for DD. That will help you the most, not allowing the trans to learn to "granny shift" when you need a balls to the wall shift.

I use O/D daily driving and T/H for killin ricers or when I feel diesel horny :rofl:

That was my next question. I have been told that too. Supposidly, you can go wot in t/h till it learns those fast and firm shifts then drive like granny in o/d for a month then just press the button and automatically have the good crisp shifts back in an instant.

What Mike L said about t/h dropping that much pressure, i didnt know. It doesent sound good to race in that mode with this going on. If the tc is locked though, does that not change the fact that the clutches need the same pressure? I dont understand the exact idea of how the system operates but that sounds like it should hinder towing and allow the trans to slip with a heavy load. I guess not though since people use it to tow on a regular basis.

 

[TrentNell]

That was my next question. I have been told that too. Supposidly, you can go wot in t/h till it learns those fast and firm shifts then drive like granny in o/d for a month then just press the button and automatically have the good crisp shifts back in an instant.

What Mike L said about t/h dropping that much pressure, i didnt know. It doesent sound good to race in that mode with this going on. If the tc is locked though, does that not change the fact that the clutches need the same pressure? I dont understand the exact idea of how the system operates but that sounds like it should hinder towing and allow the trans to slip with a heavy load. I guess not though since people use it to tow on a regular basis.

Tow Haul is simply a different program within the TCM , think of it as a transmission DSP switch ,you push the button and the TCM switches reference tables for shifting , taps , TCC apply /release ect . I think the biggest advantage for using T/H is that you can always have the taps learned to aggressive driving or WOT ,other that I have never ran faster in T/H and still race in normal to this day, but i have always had a track only that only knows WOT shifts . In fact you can make normal mode identical to T/H mode with EFI live, and the truck will feel identical in both modes , the only change when the button is pushed, is you are the telling the computer to reference the T/H taps for shift timing. As far as the TCC knock down ( pressure drop when locked ) there is no way to over come it with out modifying the Hydrolics inside the trans , AKA built trans and in factory form the knock down isn't a problem for stock power only for when you start cranking the power up .

 

[dmax06]

i always wondered this, i thought the t/h helped me, but that just may be my mind playin tricks on me. i know my tranny is hurting right now, so if the pressure drop is a major thing, i don't need to be using t/h for WOT. I've never limped mine, but it is getting really lazy at higher RPMs?? is this something to worrry about or will it be ok till i actually "limp it" a few times???

 

[TrentNell]

i always wondered this, i thought the t/h helped me, but that just may be my mind playin tricks on me. i know my tranny is hurting right now, so if the pressure drop is a major thing, i don't need to be using t/h for WOT. I've never limped mine, but it is getting really lazy at higher RPMs?? is this something to worrry about or will it be ok till i actually "limp it" a few times???

You will get the same pressure drop any time the converter is locked , T/H or not . Any time the computer see's WOT it will command lock up. ( to a certain point )

 

[dmax06]

oh yeah! well t/h doesn't really do anything? it was all in my head, haha so, my shifts bein a little lazy is my TC just having all it wants right now?.....i probably need to be thinkin bout a tranny, but i kinda want to see how far this one will go??? (not to mention the money situation)

 

[Redbowties88]

just my .02 but when i first started running in t/h i dropped 2-3 1/10's...now that could just be bacuase it was learned differently or a plethora of other things that could of caused it to run faster but ever since then t/h has become the track/haul ass mode for me:thumb:

 

[TeaBagger2006]

letting the trans learn helps it.....ive been driving with ppe lv4 tune for approximately 25k miles and the shifts are nice but i know the trans has to be hurting....never limped it but like i said it has to be hurting

 

[Redbowties88]

letting the trans learn helps it.....ive been driving with ppe lv4 tune for approximately 25k miles and the shifts are nice but i know the trans has to be hurting....never limped it but like i said it has to be hurting

well it wasen't learned when i first did it. some guy at the track just told me to do it and i was like well what the hell might as well.

IIRC i ran a 14.6 on that pass and my best previous was a 14.9. back in my slow,lifted,banks,2wd days

 

[calabria69]

T/h works great for pulling as the converter locks at a slower speed, the problem I've noticed when pulling alot in t/h is it shifts very rough the first few passes at the strip til it learns...mine definitely pulls harder in t/h when driving on the street, (I run the same times at the track with or without t/h).......

 

[JoshH]

As long as you don't put in a bigger tune for the track than what you daily drive, the transmission should not "forget" how to shift at WOT. The TCM has TAP adapts specifically for 100% APP, and driving the truck easy should not have any affect on those.