Originally Posted by 2002_Z28_Six_Speed

Unfortunately, playing with late model big blocks is a rich mans game with little aftermarket support.

Originally Posted by Oobray

For those that read my other posts. I have a 2002 Yukon XL with 8.1 and 4L80E. The tranny was just gone through and billet converter and Superior towing shift kit was added.

I just took my travel trailer and 6 people (including my 4 month old) on a 1,700 mile round trip from Oklahoma City, through NM up to Pikes Peak and back. For those that don't want to read the whole review, my impression of the towing setup is that the truck was adequate, but not fun or impressive by any means...

So the trip started going from OKC to Amarillo pulling the trailer. I pulled across the CAT scales and here's the results. I've never used a CAT scale before and I don't think I did it completely right. The scale had three sections. I put all four truck tires on one section and tried to put the trailer on the other section But it's a tandem axle and one set of tires were on the second scale and the other set were on the third set. So here are the three numbers...

1. 8,240lbs - This is with all passengers and vehicle loaded as we traveled. I think of course it would also include the tongue weight of the trailer, which Jayco states is 510 lbs.

2. 2,720 lbs

3. 1,980

4. Total weight 12,940 lbs.

So I believe the total trailer weight would be 2 + 3 + 510 = 5,210

For some reason I thought my trailer would weigh in somewhere near 7K so I was way off, which makes me even less impressed with how the 8.1 / 4L80E did towing. Here's my experience...

Towing from OKC to Amarillo I tried to stay between 60 - 65 mph. I tried to use the cruise control, but really didn't like how that was working. WAY too much shifting in and out of 4th gear. While certainly I-40 between OKC and Amarillo is "flat" it's still climbing from my house (500ft elevation) to Amarillo which is about 3,500ft. Also, while the interstate is flat, there's still rises when going over bridges etcetera. It had to down shift for ANY and I mean ANY change in elevation of the road. It also had to downshift for ANY and I mean ANY change in throttle pressure. Now, in 3rd gear it would be about 2,500 rpm and pulled pretty good. Just found inside the truck.

RPMs at 60 - 65 mph were right around 2K maybe 100 or so less. It would hit 4th but it took "effort" on my part to keep it there. Cruising at 65 I'd have to let it drop to 60 or even 55 to go over over passes or even slight changes in road pitch. If I wanted to keep a steady pace, or use cruise it would almost never hit 4th and when it did it didn't stay there long.

Heading from Amarillo north it would almost never hit 4th. I didn't manually put it in 3rd because it would almost never hit fourth on its own. I rarely ever hit 4th again while in NM and CO. In fact, there were times that it would hit 4th (if I forced it by letting off the accelerator) while going downhill but any change in throttle pressure put it back in 3rd. GOING DOWNHILL!!! And I mean a significant downhill.

It pulled Raton Pass (6% grade) in 2nd gear at 3,500 rpm and just shy of 60 mph. That was with the pedal to the floor and absolutely no more power left. But it was holding at that speed and not slowing down. I've never really pulled a trailer before so I don't know how this "ranks".

The way from Amarillo to OKC was a little better. I think because I kept it at 70 - 75 mph which put the RPMs in 4th at around 2,200 which allowed it to hold 4th a little better. But still, considering I was going downhill basically the whole time it was very aggravating to be constantly shifting out of 4th.

All of this and it averaged 6.5 mpg. This was using the odometer. The truck has 265 Cooper ST's and the MPG calculation accounted for the increased distance of the larger tires. I really wouldn't mind the MPG IF the truck performed a little better. But barely adequate towing performance coupled with the horrible MPG was frustrating. Luckily, only getting about 150 miles or so between fill ups is about when the family is ready for restroom breaks and more snacks.

The one thing I was impressed by was the transmission braking. If I put it in 2nd, even going down Raton pass it would hold a decently slow speed without having to use the vehicle brakes. That was nice. Also, the transmission temp gauge on the dash usually read around 200 deg. Sometimes a little less but never really more than that.

So I'd like to hear from all you guys that are more experienced with towing how this rates as far as towing performance. I've never really pulled any trailers so I don't how this rates as far as "normal". I just really hated the constant in and out of 4th gear. I also know that as far as mountain passes goes, Raton isn't very bad. So being topped out at only 60 mph in 2nd gear at 3,500 rpm with only a 5,200 lb trailer isn't comforting. Especially because we're really looking at upgrading the trailer in the next few years to one that's about 1,000 heavier. I've read pickup guys towing 15K + with their trucks. I don't know how this is possible unless it's the Allison that makes this possible.


Right now the truck has a new stock GM HD muffler, no cats and a K&N intake. I'm going to be getting a paper filter to replace the K&N filter so I don't have to oil it. I'm going to reserve my complete evaluation until after I get a Blackbear / Westers tune. Maybe that will wake it up. We absolutely love the Yukon for the vehicle itself, a pick up just won't work for us. This leaves me with the following options...

1. Upgrade performance in the Yukon. Engine mods, Allison swap, gear swap etc.

2. Ford Excursion with 7.3 or 6.0. With this option I'd have to upgrade suspensions pretty much right off the bat. The Ex's ride horribly!! and I've also heard the 6.0's don't really get great mileage while towing either.

3. I've looked for a D-max passenger van. But with this option, I'd HAVE to get a 4x4 conversion which would run another $4-5K on top of purchase price. Where I hunt is in a national forest and really rough roads / trails to get there. And right now I can't find a d-max passenger van anywhere in the whole country. There's plenty of cargo vans, but no passenger ones. I've looked in to adding windows to the cargo van, but I'd still be lacking the interior which I think I would not like.


So, what are everyone's thoughts?