Engine/Transmission (1998.5 - 2002) 47RE, does it lock-up in 4x4 low range/1st gear?

[EBoyts]

I almost always drive my truck on pavement, but I took it off road recently, and noticed something unusual. It was the first time I had driven while the transfer case was in 4x4 low range, and I noticed two things: 1. While in low range, shifting down from 2nd to 1st gear caused a mechanical meshing of gears that was both heard and felt, and 2. While I was in 1st, my transmission temp dropped from about 210 down to 140 (that's as low as the guage reads) and stayed there (my sensor is in the return line). It made me wonder if the transmission was in lock-up-- anybody know about this?

 

[John - K5AWO]

With the auto trannys, if you don't put it into neutral to do the shifting, there is always some small amount of stress on the splines that retard the shifting action.



When you want it out of 4x4, just go to neutral, quickly shift the transfer case to 4H. Shift to drive and pull up a few feet wiggling the steering wheel about a 1/8th turn each way. Now shift to reverse and back up at least 15-20 feet doing the steering wheel wiggle again.



Now it will be back in 4H and you can go about your business without concern for it being still engaged.



All you are doing with the above is removing the stress on the splines so the shift motor can disengage the front axle easily. No black magic.

 

[EBoyts]

Thanks for the info about the transfer case, though I think my question may have been worded a little unclear-- I understand the transfer case can be under stress when shifting between drive modes, I was talking about already being in 4x4 Low, and shifting between "D", "2", and "1". I was descending a jeep trail and going back and forth between D and 2, when I shifted into 1 for the first time-- that's when I got the mechanical sound/feel and that's when my transmission started to run lot's cooler. That's why I wondered if the transmission input/output shaft were locked up. Does that make sense?

 

[John - K5AWO]

Oh yeah..... now I see what you mean. Yep, when you locked it into 1st gear manually, the TC locked up making it like a manual gear box.



ergo no more internal fluid slipage in the TC. TC cooled right down fast.



Just be real careful about down shifting when in 4 Low. The gear reduction is so great, and the Cummins is not very forgiving of sudden shifts in RPM... . If you are "above" the speed/RPM limit for the next lower gear, you are going to get some mechanical sounds you won't like.



I like to brake it slower, then down shift and increase RPM to the desired descent speed. Lot easier on everything.

 

[bmoeller]

If you have to stop quickly, put in neutral before slamming on the brakes. Could blow a brake line. Had a brain fart and forgot to do that on my previous Ford. With the torque muliplication from being in 4L and all the torque that the Cummins has, it can very hard to stop, if not in neutral. Make sure to be easy on the throttle, unless you want to run the risk of breaking something. Esspecially if in 1st (and maybe even in 2nd) gear at the same time.

 

[EBoyts]

Thanks guys, for the words of caution-- I'll be a little more respectful next time I find myself in 4x4 low.