Chevy and GMC Duramax Diesel Forum banner

1 - 20 of 28 Posts

·
Registered
Joined
·
117 Posts
Discussion Starter #1
This friday is the last night of racing in topeka kansas for the year for test and tune and it will be the first time runnin this truck the tranny is built but are you guys runnin in tow/haul or not.
 

·
Premium Member
Joined
·
298 Posts
i believe the t/c will lock up in either mode once the throttle is @ 100%. i dont think it matters which mode you use :gearjamin
 

·
Registered
Joined
·
1,069 Posts
i believe the t/c will lock up in either mode once the throttle is @ 100%. i dont think it matters which mode you use :gearjamin
Not according to my CTS it doesn't.

In tow/haul it will shift much faster and lock the converter starting in 2nd gear. I would suggest you use it.
 

·
Registered
Joined
·
2,130 Posts
it's called tow/haul ass mode for a reason

use it.
 

·
Registered
Joined
·
140 Posts
Not according to my CTS it doesn't.

In tow/haul it will shift much faster and lock the converter starting in 2nd gear. I would suggest you use it.
From what I've observed on my CTS, from a dead stop @ WOT, w/o T/H mode, the Transmission will lock the TCC starting in 2nd gear. Tow/Haul does seem to be a faster shift yet though, as I believe it raises line pressure.

I'd do it still, no harm.
 

·
Its just a worktruck
Joined
·
13,908 Posts
From what I've observed on my CTS, from a dead stop @ WOT, w/o T/H mode, the Transmission will lock the TCC starting in 2nd gear. Tow/Haul does seem to be a faster shift yet though, as I believe it raises line pressure.

I'd do it still, no harm.
False. Line pressure drops ~100 psi when the TCC locks. If you dont have a built transmission with the internal pump mods using tow/haul for anything but towing or hauling is pointless and is doing harm to the transmission.
 

·
Registered
Joined
·
2,130 Posts
False. Line pressure drops ~100 psi when the TCC locks. If you dont have a built transmission with the internal pump mods using tow/haul for anything but towing or hauling is pointless and is doing harm to the transmission.
so you are saying locked converter is bad for stock(ish) transmission?
 

·
Its just a worktruck
Joined
·
13,908 Posts
With the power turned up far beyond stock levels, yes.
 

·
Registered
Joined
·
6,193 Posts
people report running faster times without tow haul...i dont use it.
 

·
Its just a worktruck
Joined
·
13,908 Posts

·
Registered
Joined
·
1,069 Posts
False. Line pressure drops ~100 psi when the TCC locks. If you dont have a built transmission with the internal pump mods using tow/haul for anything but towing or hauling is pointless and is doing harm to the transmission.
First I've ever heard of that. What's your source?
 

·
Its just a worktruck
Joined
·
13,908 Posts
Mike L.

T/H does nothing more than extend shift points so that your truck will get a better running start between gears under load. T/H locks the converter clutch in second gear to cool the trans and let the turbo pick up the load instead of the converter mutiplying uneeded tq. T/H also drops trans psi by 100 psi so you just lost holding power to your clutches. T/H works great as a grade break because it keeps the converter clutch locked during down shifts and that allows engine braking. It is not a magic pill. It is good for towing heavy loads and keeping your trans cooler.
 

·
Registered
Joined
·
212 Posts
I run in tow haul and I noticed it drops my ET by 0.2 comapred to not running in tow haul. I also just had my TCM reprogrammed to shift a higher RPMs when in tow haul because it seemed to shift too soon before. just my 2cents
 

·
Registered
Joined
·
379 Posts
Shit! Every time i get on it in my truck i put in in T/H.... better stop haha or trans will come sooner than i want it too. Why does it feel so much faster in T/H? Because its slipping the converter that bad in regular??
 

·
Registered
Joined
·
6,193 Posts
Weird, my times are always better in T/H...
stock turbo vs aftermarket. you dont want your TC to lock till you are on top of the charger and boosted. with a stocker it doesnt matter. but with a larger turbo, you can lose alot of power letting the truck lock up before your charger is spooled
 

·
Registered
Joined
·
1,069 Posts
Mike L.

Originally Posted by Mike L.
T/H does nothing more than extend shift points so that your truck will get a better running start between gears under load. T/H locks the converter clutch in second gear to cool the trans and let the turbo pick up the load instead of the converter mutiplying uneeded tq. T/H also drops trans psi by 100 psi so you just lost holding power to your clutches. T/H works great as a grade break because it keeps the converter clutch locked during down shifts and that allows engine braking. It is not a magic pill. It is good for towing heavy loads and keeping your trans cooler.
Where in there does it say anything about harming the transmission by using T/H while not towing?
 

·
Premium Member
Joined
·
9,706 Posts
Chris is right. Pressure drops when the converter locks.

Sent from my phone, probably while driving and eating a sammich
 

·
Registered
Joined
·
6,193 Posts
Where in there does it say anything about harming the transmission by using T/H while not towing?
it doesnt directly state damage will be caused...but when the TC locks the pressure does drop. thats less pressure to apply the clutches. less pressure holding the clutches = better chance of slipping the trans. it wouldnt be a problem in a STOCK tuned truck. but when you start testing the limits of a stock tranny, it matters
 
1 - 20 of 28 Posts
Top