I just got back from a camping trip with my family to Yosemite/Cherry Lake area in the Sierra's. I pull a 23 foot travel trailer that weighs about 6000 lbs loaded. I also have the bed of the truck loaded with firewood, bikes, ice chest, etc. This is the most weight my truck ever hauls/pulls. It's bone stock except for 285/70-17 BFG AT's.

There's a pretty long and winding grade called Priest Grade that we have to go up. It's about 8 miles of uphill switch back 15 to 30 mph all the way up. When you get to the top it straightens out and you can pick up speed to about 50 mph. My truck runs about 210 degrees (according to the stock guage) up this hill, when it usually runs under 200 on flat ground.

When I finally get to the top and accelerate, when it shifts into 3rd in tow/haul mode, it slams into gear and shakes the whole truck. So much so that my wife looks at me and asks what happened.

This has happened twice to us now, once last year and now this year at the same exact spot, into 3rd gear. It has never happened anywhere else, and we pull the trailer all over northern CA camping. But the one thing about this grade is it's so long at 15 to 30 mph, the torque converter never locks up. Then at the top, when it does lock, it slams hard.

Is this something I should worry about? Truck pulls fine the rest of the way, and has been fine since. I don't work the truck hard, and I take it easy on that grade.

Just wanted to get opinions to see if I should take it in and have it looked at. It only as 14k on it. Thanks.

 

Ah, further reading and found this post.

https://www.dieseltruckresource.com/...d.php?t=210153

Looks like nearly the same problem I have, but the grade I'm going up is not nearly that steep, maybe 6 or 7%, and the temperature at that time of the day when I went through was around 82 degrees. Plus mine makes one hard shift into 3rd, hit the top of the hill about 10 seconds later and it's down hill from there.

About 30 minutes later, I was on a 1 lane road heading to Cherry Lake, coming out of a canyon, slower speeds, steeper grade and when I got to the top, it shifted into 3rd and I was expected it to slam again and it shifted fine.

 

Your Tranny does not like the Heat that you put in it at those speeds. I wonder if you placed the gear selector into 2nd if that would help. Tranny cooler with aux fan would also be a great idea before the next trip. Turn it on right before you go up that hill and you should be fine! JB

 

If you are going that slow for any lenght of time you need to manually down shift to 2nd so the TC will lock. Doing that will get rid of your heat problem and the aggressive shifting and lockup.

 

Ditto to no6ohno. Also an occasional change mind shift harshness has been normal on older tranny. Remember lift foot 1 -2 shift in past.

 

Ok, I'll try that next time. I didn't realize manual 2nd gear locked the torque converter in tow/haul. Guess if my tranny got that hot, I better change out the fluid. Thanks.