doggy 4.0

[my91yj]

Hey guys, I'm new here, and I need a little help! I've got a 91 YJ with the h.o. 4.0. It has no power "off the line". I'm running 35's with 3.55 gears. I know you might say it's the tire size, and lack of gears, but it was exactly the same with stock size tires. I would expect a moderate power loss with the 35's, but this is crazy. Any ideas would be great! Thanx in advance

[cbrazor1]

i know you dont want to here it but 3.55 and 35s = no power

[ECV Jeep]

I'ld have to agree with CB on this one. Your gearing and tire size are sort of a mismatch. With that in ind, realize that the 4.0 is not an off the line smoking engine. It does provide good torque, and is very reliable. If your engine seems to be running well, and only lacks that extra get up and go, I would lean towards the re-gearing option. Just a thought.

[Shadly1]

This should get you off to a good start.
http://store.summitracing.com/partde...5&autoview=sku

Pair that up with an upper intake cleaning and you'll be running great engine-wise.

[VVjeepfreak]

What trans do you have with it ?

[my91yj]

It has the auto trans. My buddy has the exact same set up, and has way more power than I have. I agree I need gears, but why would it be the same with small tires?

[Shadly1]

It has the auto trans. My buddy has the exact same set up, and has way more power than I have. I agree I need gears, but why would it be the same with small tires?

You might have some sort of slip in the tranny. That's a LOT of torque to put on that little guy. I'd imagine your foot is into the skinny pedal quite often to push those tires around with your gears. Your torque converter might not be up to the task. Try a tranny service with some really high quality ATF, like Royal Purple or Redline. Even if that's not the problem, it's pretty cheap and you can cross that item off your list. Keep your fluid AT the full mark with a level tranny. Too little and your tranny will slip and burn. Too much and you'll spit it out on your engine and driveway.

[my91yj]

I'll try that. Thanks shadly!

[VVjeepfreak]

I have the A904 auto in mine and I am still on the 3.07's with 33's. It still had alot of get up.