npk

i pulled my boat today for the first time with my 95 cherokee sport automatic. the boat is a 15 ft aluminum flat bottom with a 40 horse outboard. i have no idea what it weighs. i will call it 1000 lb including the trailer. the xj did fine up to 55 mph. if i wanted to drive 65 mph the engine struggled to maintain speed without kicking down a gear. what can i modify to give me more mid-range torque? the xj already has a "rock-it" air filter kit and a high flow exhaust. what internal engine mods should i look at? this problem has me a little concerned. i am running 31" tires right now, but would like to put some 33's on it. that will drop my rpms and then it will pull worse. what should i do?

thanks

jeff2285

buy a truck or live with it

Hoooper

RV cam would make a big difference for towing. Intended to just make brutal amounts of TQ

dev_daddy

Honestly just one numerical figure lower in ratio in your differential That'll help towing more than anything. You can mod your engine all day, but gears will make a bigger difference.

npk

tying not to run 2 vehicles. i have my truck for sale. the xj already has 4.10 gears. if i switched them out i would like to be below 2500 rpm at 70 mph on 33 inch tires. i saw a chart posted that told the gear ratio you needed to stay at factory rpms when you increased tire size. the problem is that the chart seemed to be way off. can anyone tell me the output ratio of my overdrive? i could do the math if i had that number. i don't know the model of tranny i have. i assume it is stock. it's a 95 cherokee sport 4x4 automatic.

dev_daddy

Then you have the AW4 tranny. I'm not sure what the overdrive ratio is... but i know there are people on here who do!

mountaineerjeff

im pretty sure its .75

HCCAFan

I have a 5 speed and struggle to pull similar weight over 70mph. That said, my gears are stock.

In Tow/Haul mode on modern automatics, they usually don't go into overdrive anyway so you might be about normal. The boat might not be heavy but there is a lot more wind resistance. I can get better mileage pulling a 5000 pound truck on a trailer than I can pulling a 2500 pound enclosed trailer.

dev_daddy

And with my experience towing with my jeep, even with a light weight trailer and nothing to catch the wind, it struggles as well. But going up a gear number would benefit. Or look into a cam.

cdawall

its .75 i have no idea why you are having issues at 55mph with 4.10s you should have plenty of midrange torque to pull that small of a load. thats 4 people in the jeep with camping gear and mine has never had that issue.

dev_daddy

Good point...

Sure all cylinders are firing?? Haha

Hoooper

31s and 4.10 is close to stock, but bigger tires still take more power to turn. Add in weight and wind resistance...

I would bet you're pulling more like 2k pounds. Unless your boat is just a shell with no motor or seats and your trailer is super light. The trailer alone for my 20ft boat is 3k lbs

cdawall

yea thats cool except mines 31s with 3.55s and it can pull more than 1000lbs@55mph in OD

Hoooper

1000 lb non aerodynamic weight or 1000 lb of people and equipment IN the jeep? Theres a significant difference between putting stuff in the jeep and towing. And I'm pretty sure its a good amount over 1000 lbs for that trailer. Maybe you should be asking if it feels fine when not towing... Because if yes then it's probably not a problem with not running right

cdawall

flat pulled a ranger which is roughly 3500lbs all the way up to 65mph just fine but that was bone stock tires and all.