New owner of a Suburban/TT combo

Its your axle ratio,
The last motorhome I had was a 81 winnebago and it had 4.56 gears with a 454 and my current 99 c3500 has 4.10s with a 454
IMHO ya need a least 4.10s for towing.
Ken

Gear ratio..

I also would check the brakes on truck and trailer..

any drag will greatly reduce gas mileage .. just because they work OK does not mean they are retracting correctly.

and HOW DARK is the brake fluid????????? it matters.
should be clear (like water).

Thank you for the replies. I will check the fluid and change it out. I'll also jack up the wheels and give them a spin.

I don’t know what the weight of your loaded TT is, but if it’s 5000# plus your experience doesn’t sound too unusual. Weight really becomes noticeable when you’re climbing grades and it’s one of the reasons I pull a small 3000# TT. I spend a lot of time in the mountains and I have a low tolerance for slow, high rpm climbs.

If you did a lot of climbing that might explain your gas mileage, too. My overall average towing is 14 mpg, but the very worst I’ve gotten is 9 plus. I generally do a little better than that, though. Shorter gearing would help when you’re climbing grades. The tradeoff is a little higher rpm on the flats and a possible slight reduction in gas mileage.

First, unhook that log trailer behind you and it will be easier to tow! :R :B

I'm guessing you don't have fuel injection? How does it tow uphill? Does it seem like it is really dragging, or does it seem like lots of power?

Automatic? If so, a sign of a gear ratio problem is always shifting gears, where one seems too much revving and the next doesn't have enough power.

1989 454 getting 10mpg towing a high walled RV? I think your expectations are too high. The 2000+ 8.1L is the most fuel efficient of those big blocks and they don't get 10mpg either.

As a comparison, my 2002 8.1L K2500 Suburban towing an 8K pound TT gets 8mpg if I tow at my usual 62mph. No problems maintaining speed uphill.

Steve

karitoki wrote:
In reading threads on this forum it's maddening to hear about MHs with 454s that pull big trailers and get 9-11mpg, and haul up hills on que.

Don't get too down on your combo based on what other people post on these forums. There are plenty who are, ummm, optimistic on their mpg calculations. Sounds like you are about where I would expect, IMO.

I can tell you, my dad had a mid-80's Class A MH with a 454 that I drove to the dunes towing a relatively light flatbed trailer with atvs on it many times through the mountains of So. Oregon to Coast. It did not get 9 mpg! Maybe 5-6 mpg on a good day is more like it. It used 2nd gear plenty going up the hills, too.

Thanks again for all the feedback! I wish I could post a picture of the rig; it's really nice for an '89. BTW, I only paid $1,300.00 for it. Tires (8 lug wheels) all were 90%+ including a set of studded tires on rims. It came with a maintenance file about an inch thick! It seems like the PO took it to the shop whenever it farted! Anyway, It has the Garnet Red cloth interior, 3rd seat and power everything. The only thing wrong with it was it had rust/rot in several places. The hood, one of the doors under the trim, and the area under the barn door weather stripping were especially bad. Lots of sanding, some Chassis Saver, Bondo, and Olympic white paid and it doesn't look too bad.
Here's a couple of links to a GM forum I posted pics at:

http://www.gmsquarebody.com/forum/showthread.php?t=7309&highlight=karitoki

http://www.gmsquarebody.com/forum/showthread.php?p=181151#post181151

Well, I think I found one source of my power/economy problem; The engine is only running on seven cylinders! I had thought something wasn't quite right, but a neighbor with a lot more experience than me told me is was only running on 7. Crap.