Loss of power?

Gris · **Posted:** Sun Jun 25, 2006 8:10 pm

I'm not exactly what change I made that caused this, but I'm noticing a huge loss of power in my jeep.

it's an '02, 3.7 5-spd. About 2 months ago I did a complete tune up and that's when I noticed it. Only problem is, the place that did the tune up also installed my 265/70s at the same time.

I'm not sure if this loss of power is coming from larger tires, crappy plugs, or something else.

What I mean by loss of power is that I have to downshift from 5 to 4 on normal highway inclines, nothing steep. Acceleration is way down and starting in 2nd is almost impossible. Not that starting in 2nd is a great thing, but the jeep used to do it and now it's not so easy.

Anyone have any suggestions?

tjkj2002 · **Posted:** Sun Jun 25, 2006 8:14 pm

My guess is the tires,I lost alot due to my 265's but got some back when I switched to 4.10's.Big tires and manual trans with no gear swap equals big loss of power unlike having a auto(they are a little more forgiving then sticks).

JFortier777 · **Posted:** Sun Jun 25, 2006 8:29 pm

I second the accusations towards the tires.

When I slipped on my 265s I nearly cried when I got back on the road.

Mutt · **Posted:** Sun Jun 25, 2006 8:38 pm

JFortier777 wrote:

I second the accusations towards the tires.

When I slipped on my 265s I nearly cried when I got back on the road.

I'll third it, I've got power loss and my mileage is in the toilet. I'm ashamed to disclose how bad my mileage is.

tjkj2002 · **Posted:** Sun Jun 25, 2006 8:49 pm

Well if your getting worse than 12mpg don't feel bad Mutt,Opps, that's my 100 lb right foot talking again.If and I mean if I drive normal I can get 18 to 19 mpg.(lifes a drag race,I'm go'in to win at all cost(in gas that is))

PitViper · **Posted:** Sun Jun 25, 2006 8:52 pm

I know what you guys mean

makes you want a CRD .....

Gris · **Posted:** Sun Jun 25, 2006 8:52 pm

Mileage doesn't seem that bad actually. I always got around 270 miles before the light dinged. Now I get around 240. But considering I'm using a 2" taller tire, I think it about evens out.

tjkj2002, what did you mean by "when I switched to 4.10's"? I'm not sure what a 4.10 is.

tjkj2002 · **Posted:** Sun Jun 25, 2006 8:59 pm

4.10's are is my gear ratio in my diff's,switched from 3.73's.The higher the number the lower the gear is(more lowend torque,less top end speed),the lower the number the higher the gear ratio is(less lowend torque,more highend speed if you have a stronge engine).Since your stock tires are about 29" going to almost 32" your 3.73's gears really should be changed to a 4.27 gear ratio but can't do that in a KJ so 4.10's is the next best thing to get back into the stock final drive ratio to get your power and mileage back.

Gris · **Posted:** Sun Jun 25, 2006 9:33 pm

Thanks for the info!

broncsrule · **Posted:** Sun Jun 25, 2006 11:33 pm

Do the new gears help when wheeling? Crawling downhill for example? Sometimes I am jealous of my fellow Liberty owners w/automatic trannys while going down steep inclines.
How is the install on 4:10's?

JFortier777 · **Posted:** Mon Jun 26, 2006 6:26 pm

broncsrule wrote:

Do the new gears help when wheeling? Crawling downhill for example? Sometimes I am jealous of my fellow Liberty owners w/automatic trannys while going down steep inclines.
How is the install on 4:10's?

You would be even more jealous seeing me go down a steep hill backwards in the snow, in 1st gear.

JFortier777 · **Posted:** Mon Jun 26, 2006 6:31 pm

EDIT:doubel post sry :cry:

Mutt · **Posted:** Mon Jun 26, 2006 6:33 pm

JFortier777 wrote:

EDIT:doubel post sry :cry:

See the "X" button on your post, next to the quote and edit? Hit that, it will delete your post.

Jeepjeepster · **Posted:** Mon Jun 26, 2006 7:02 pm

broncsrule wrote:

Do the new gears help when wheeling? Crawling downhill for example? Sometimes I am jealous of my fellow Liberty owners w/automatic trannys while going down steep inclines.
How is the install on 4:10's?

I dont understand that? The 5speed will hold you back much better than the auto tranny. :?:

KY Liberty · **Joined:** Sat Jul 09, 2005 1:46 pm **Posts:** 1195

Those 265 BFG's are 51 lbs each. The stock 235 SRA's are 32 lbs each. The 265's are 30.7", and the 235's are 29" diameter. The 4.10 gears will get you most of the difference back from the height change, but that's a noticeable difference in rolling mass. You'll have to pick up some more torque too. I would recommend testing your brakes. You may want some powerslots. I needed them up front with my 245/65R17's because of the worthless drums in the rear.

broncsrule · **Posted:** Mon Jun 26, 2006 10:38 pm

That's what I used to think. What I am talkining about is very steep crawling... The automatics can apply their brake to stay in control. The manuals have a clutch to deal with. If the engine braking isn't enough, you have to brake (and usually clutch to keep from stalling). So, what I am asking is does that gear ratio make a difference when going extremly slow?
Does this make sense?

KY Liberty · **Joined:** Sat Jul 09, 2005 1:46 pm **Posts:** 1195

The bigger gears will help the most while going slow. If you've ever ridden a 10 speed bike, think about the rear sprockets. If you're going up a steep hill, you want the largest sprocket. You have to pedal more times to go a certain distance, but it's easier to do. Going to 4.10's allows you to run a higher rpm for more power to the ground at the same speed. The drawback is they do the same thing at highway speeds and decrease your gas milage.

Gris · **Posted:** Tue Jun 27, 2006 10:28 am

broncsrule wrote:

That's what I used to think. What I am talkining about is very steep crawling... The automatics can apply their brake to stay in control. The manuals have a clutch to deal with. If the engine braking isn't enough, you have to brake (and usually clutch to keep from stalling). So, what I am asking is does that gear ratio make a difference when going extremly slow?
Does this make sense?

I'm sure a 4.10 would make a slow crawl faster, but tbo, I've gone down some pretty steep crap in 4lo 1st and barely had to break at all. you gotta remember that top speed in 4lo 1st, gunned, is like 4mph

broncsrule · **Posted:** Tue Jun 27, 2006 10:13 pm

There are times when you don't have to use your brakes but I have been on plenty of trails in Moab and Colorado where engine braking is not enough (unless you want to kill yourself or the Liberty). There are times where 1mph is too much let alone 4mphs. It sounds like the 4:10s would help some.

How do you go about getting 4:10s? AFtermarket? out of another used diff?

KY Liberty · **Joined:** Sat Jul 09, 2005 1:46 pm **Posts:** 1195

You can get the rears, and a rebuild kit from rocky-road.com . The fronts don't fit. My mechanic found a doner low milage front diff from a 4 cyl while my Jeep was on the lift as we were learning that even though people sell front gears for the Liberty, none of them fit. The dealership is the only way to get the 4.10's for the front, and they want way too much for them.

Loss of power?

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