First gear is 2.71:1. Reverse is 2.88:1. All else being equal the torque converter will do less work and slip less in reverse than first gear.

The reasons that the torque converter gets so hot in reverse is that it almost always is very low speed so that there is a lot of torque converter slip. First gear usually used at low RPM for a second or two as the truck accelerates. Reverse can be at low speed for a long time, depending on how good the driver is at backing up.

The other reason is that there is little or now airflow over the trans cooler in reverse. You don't have this problem going forward.

 

Thanks for posting the reverse gear versus 1st gear ratio, Mark.

Time for an electric fan on the trans cooler (and all that implies)

 

Hey Mark, your a master of these 4R100s, does what I posted sound legit? I've talked with a couple of transmission shops and have gotten some differing opinions but between talking to them and doing some of my own research the posts above are the conclusions that I have arrived at. Based on my previous posts, what would your diagnosis be and what would you expect to need replacement when I have the transmission dropped?

Thanks

 

SLE I would like to be there and see the BSEG on your face the first time you pull after the gear change . I checked and you will only be 50 rpm less than I am at 60 mph in third gear with your 285/75 32.8" tires 4.56 gears and my 215/85 30.4 tires 4.30 gears. You will also find that pulling in OD is not a problem at all and the same goes for backing the trailer.

Denny

 

Yeh, you know my history Denny. I've went back and forth on this gear change a number of times over the years. Right now I'm currently pulling a 31' two slide fithwheel that has a GVWR of 11,500#s and my 20' Yarcraft boat that I believe to weigh around 4,000#s when full of gear and fuel. The last couple of years I have really struggled pulling this load. When conditions are right and the wind ISN"T blowing, it does alright. Actually, it even kind of impresses me considering what I'm putting the truck through. On the other hand anytime the wind IS blowing I almost dread the trip to a from the lake as I know I'm gonna struggle to stay in third gear and will be in second alot. I'm don't know if I'm asking for a miricle out of this ol Superduty but I'm really expecting the gears to make it considerably better, maybe I'm setting myself up for disappointment, I sure hope not!

 

The stock programming will lock the torque converter in each of the forward gears if the go pedal is pushed far enough and the engine speed is high enough.

The gauge will sit right in the middle until the trans reaches 230°F.


If you locked the torque converter in reverse you'd need to be going at least 10 MPH or you'll stall the engine. That's why it doesn't lock in reverse.

Yes, that's how it works.

There is a better seal made from Viton that works much better.

Higher numerical gears will make a BIG difference in transmission and torque converter temperatures. I think getting the gearing right for your load will fix your problems.

 

Thanks Mark.

 

I now you will be happy with its performance after the gear change . I pull a 16K 5ver and a 1200 lb boat behind it at times, I gross 24K without the boat and pull it all over the country, being able to stay in OD makes the transmission run a lot cooler.

Denny

 

The appointment has been made for a freshing of the tranny and a new set of 4.56 gears for the front and rear. The truck will be dropped off Monday morning for the tranny work and the gears will follow. Sounds like it'll be 2-weeks or so before I get it back but I will be anxiously waiting to hook up to the train at the end of the month as I have a 9 day camping trip planned. I'll certainly report back with results when it's all said and done. Also had a good talk with mike about getting some updated tunes for the new gear set and he also mentioned that with the 4.56s it should be a real stump puller. We'll soon see. Thanks for the help guys.

 

After reading guru's post I'm going for the coils, I've done everything else, still get the OSS and VSS code and just a very slight misfire and eventual stall in R or D, but not in P or N. I was leaning towards PCM replacement tomorrow, been a friggin aggravating week for me.

 

My O2 sensors were finally my problem especially downstream had 2 shorted wires and was kicking on my OSS and VSS codes

 

Sorry to hear about your trans troubles, I've been there many times with GM vehicles and it's never fun or cheap. I know this is not going to help save this trans, but I always put my truck in "4-low" when jockeying my trailer around. That way it's easier on the trans and you don't even need to touch the throttle most times to get it to move easily.

 

Sand_Man, using 4-low for jocking trailers is the right thing to do. My trany guy even said that it would of help avoid what happened. I should probably clarify that the ol 4R100 isn't completely toast, it simply blew some fluid out of the front seal and it may or may not leak again. Since I'm pretty particular about my stuff I'm gonna have the trans dropped to repair the font seal and it only makes since to have them freshin up the rest while it down. In all actuallity I might have been able to get away with changing the fluid and filter and I might not have had another problem. It also gave me an excuse and some amunition to get the gears changed when talking with the wife, gears being something I've talked about changing for years!

Stopped by the shop to grab my phone charger and the shop owner said parts should be in today (firday) so he planned to hit it hard next week. I cann't wait to get it done and see the difference when towing the train! Should make a new truck out of it!