So last spring I installed a DTT convertor and VB. Drove it to Moab towing about 7000#(trailer, jeep and gear). Did great, lately though I've noticed a shudder when shifting thru the gears while towing my garden tractor/trailer(4000#), figured it was a u-joint starting go.

Last weekend I went camping in Radium BC, its a pretty steep hill going up there and I was pulling about 9000#(camper,trailer,jeep, gear). Everything was going great, truck was pulling good, untill I started up the first steep hill. Truck shifted into third gear and then even though I had my foot into into the TC locked up. Immediatly the truck started shuddering, not violently but definatly noticable, also power seemed to drop like the engine was lugging, it was showing 1800rpm on the tach at that point, about 2100rpm before it locked up. This happened evertime it locked up. It shuddered in OD lockup as well but not as bad(probably cause there was less load).

So is it supoosed to lockup in third when hauling with your foot in it? Did I overpower the lockup clutch? I had the juice on "2"(tow mode) at the time but raising or lowering it didn't seem to make a difference.

Any thoughts? Can I manually lock out the TC lockup when pulling hard?

 

Call Bill K.

 

Agreed on ncalling the builder.

You may have TC cycling that is so common. Did you install the noise filter?

I am sure Bill will get you fixed up. After re-reading your post, you may have a different issue altogether. It's possible there is another internal issue that wass not addressed with the TC and VB.

Dave

 

Noramlly when using a DTT TC and VB the clutches need to be upgraded as well. Ditto on calling Bill.

 

Hm, not sure if youre mistaking the symptoms of higher trans pressure with shudder. Every gear change with a DTT setup should give you a little kick in the pants. especially 1-2 if youre driving slow. The VB and the TC should be a good reliable combo. I think some of the full build DTT updates include the overdrive and the clutch packs though.

 

I'm quite certain its not the clutch packs slipping, tranny temps are low and everything is fine untill lockup.

What controls lockup? Seems odd to me that it would go into lockup in 3rd gear at all. I thought lockup was just a fuel saving feature that is supposed to come on while cruising down the highway. I cann't imagine why you would want it to lock up when pulling a hill with a heavy load.

My sister has an '01 1500 5.9 gasser. You can feel the tc unlock when cruising on the highway. It drops out even climbing just a slight hill.

 

TC lockup is controlled by the PCM. It needs a minimum threshold of voltage from the APPS as well as meeting the other factors of the PCM.

Lockup in 3rd is there to helkp control heat and to add effenciency if OD is locked out. Under normal use, you rarely feel the 3rd gear lockup, but it's there.

Don't think that there is no way your clutches are slipping. It is very possible. As the TC locks up, it becomes the dtrongest clucth in the trans. Sometimes, this lockup will overpower the weaker clutches as that torque has to go somehwere.

Again, it's hard to say without looking at it. But low tranny temps are not an indicator that you do not have slippage. When I had my trans rebuilt, we found evidence of slippage in gears that had shoed no signs of any issues.

Dave

 

Why would you want to run unlocked? Unlocked wastes power and build heat in the transmission.

Eric

 

Torque covertors multiply torque. More torque is good for towing.

 

Torque converters cant create torque. The reason it drops RPM's when it locks is because it is wasting power when it isnt locked.

 

They create torque the came way a differential does, more rpm in/less rpm out but more torque.

 

Personally...with my DTT unlocked, it pulls as well as it does locked...but I only lose about 250RPM going to lockup. So I don't see the locked/unlocked while towing as an issue!

BUT, the 3rd gear lockup is normal.

Chris

 

From wikipedia: http://en.wikipedia.org/wiki/Torque_converter


"A torque converter is a modified form of a hydrodynamic fluid coupling, and like the fluid coupling, is used to transfer rotating power from a prime mover, such as an internal combustion engine or electric motor, to a rotating driven load. As with the fluid coupling, the torque converter takes the place of a mechanical clutch. Unlike a fluid coupling, however, a torque converter is able to multiply torque when there is a substantial difference between input and output rotational speed, thus providing the equivalent of a reduction gear.

 

Thanks, I was wondering about the 3rd gear lockup. How heavy do you tow? I know that when pulling light(5000# and under) its fine, when going into lockup in 3rd there doesn't seem to be much difference. But pulling heavy(9000#+) it definatly didn't like going into lockup.

Does anyone tow heavy and use a manual switch to lockout the lockup?

 

I don't that often...but my charger is laggy, and doesn't like the converter locked up until you're cruising. I've towed anywhere from 7Klbs to 15K lbs...doesn't really make a difference in the tranny, only in airflow

My tranny is setup for racing...hard shifts, and a tight converter...not ideal for towing!
Chris