1882

I have 35's on my '02 and was wondering something lately: since the speedo is off about 6 mph or so does this delay the lockup of the TC? The reason I ask is because the lockup is controlled by mph correct? Isn't the lockup somethiing like 40 mph or so? Would that mean that if the speedo reads slow due to the larger tires wouldn't the TC lockup later because the truck thinks it is going slower than is really is? For example if the speedo reads 40 and I am actually going 45 or so does the TC lockup according to what the speedo reads or my actual mph? Confused here...

98whitelightnin

It shouldnt have anthing to do with mph, it should be rpm. If your taking it easy it will lockup earlier than if your WOT.

Fishin2Deep4U

A few things control lockup. One of which is APPS position as it relates to voltage at the PCM. So, more throttle sometimes delays lockup as well as the other parameters.

Dave

1882

Very good to know, thanks fellas! I wonder if that TC controller thing from ATS might be a good idea if I don't tow and take it fairly easy until she's up to speed?

RowJ

No hard evidence but my 47RE lockup seems to be controlled by torque. The more torque you are using, the slower the converter is to lock up.

From the Service manual....
The torque converter clutch is controlled by the Powertrain Control Module (PCM). The torque converter clutch engages (locks up) in fourth gear, and in third gear under various conditions,
such as when the O/D switch is OFF, when the vehicle is cruising on a level surface after the
vehicle has warmed up. The torque converter clutch will disengage momentarily when an increase in engine load is sensed by the PCM, such as when the vehicle begins to go uphill or the throttle pressure is increased.

I have 35" tires also. They may slow the lock up process a bit (due to more engine load, but not enough to be real noticable.

JMO - RJ

nitrousn

Not true mph will be a big factor in control. The governor works off output shaft speed which will greatly control the shifting functions. The pcm sees many inputs in controlling shifts. As said throttle position, governor sense on shaft speed, temperature, stc. all play a roll on when the lockup is told to engage.

DMcPherson

yes, it typically locks up at 50 mph with no load. so with 35's it will lock roughly 45 on the speedo. but still being 50 mph. thats how mine has been anyway

1882

Thanks fellas, man I love this site!

high bid

lock up in o/d is about 53mph for me