93 YJ 6 cyl under-performs

[Triggersights]

I have a YJ that seems to be in good shape. Its a 5 speed manual. It runs great around town but out on the highway I have to keep the pedal to the floor board to stay at 70. If I pull my little EMPTY flatbed trailer, forget about 5th gear and plan on 65mph tops. I have 30 inch mud tires and a 3 inch lift. I just thought this was a real under performer for a 6 cyl. Is this normal? The jeep runs smooth no problems. I was told it had the next step up in gears also but I don't know I'm not a mechanic. Do these things have governors or is this just normal? I had a 2001 cherokee 6 cyl that would pull a camper all day at 70mph and beyond. Any comments or suggestions?

 

[Bounty__Hunter]

It's normal for that jeep as you have slightly over-sized tires and very tall axle gears (3.07). Your best bang for the buck would be to find a pair of axles from an '87-'95 Wrangler with a 2.5L engine and 5spd, these will be geared 4.11 and return your performance to what you expect.

 

[superj]

the 5 speeds have 3.07 also? i know both automatics we had were 3.07s and would do over 80 all day long. i thought the standards had different gearing

 

[superj]

and we actually had 31s on both for a while with no problems. i think he has something else going on

 

[Bounty__Hunter]

The 4.0L and 4.2L 5spd in a YJ typically came with 3.07 gears. The manual has an overdrive where the auto is like the manual's 4th gear 1:1 ratio.

There could be other more minor performance issues, but I think the gearing and tire size are the largest issues.

 

[Triggersights]

The 4.0L and 4.2L 5spd in a YJ typically came with 3.07 gears. The manual has an overdrive where the auto is like the manual's 4th gear 1:1 ratio.

There could be other more minor performance issues, but I think the gearing and tire size are the largest issues.

I wonder if I could keep the hieght on the tires but changed the width if that would help then. I'll see if I can embed a pic. Thanks for the help.

 

[Triggersights]

Here is a pic if I did it right. One mechanic serviced the differentials and said I had 4.11's.

 

[Triggersights]

My pic file was too big. Here is a youtube link that shows the jeep

I don't have enough posts to show a link yet

 

[Triggersights]

You have to have 5 posts to embed a link in a post.

 

[Triggersights]

I think I'm there now. Lets try that youtube video again.

 

[Triggersights]

Maybe seeing it will help. I knew the 4 cyl struggled with large tires but I didn't know it would affect the 6 cyl.

 

[superj]

i have 225/75/16 on right now, which i believe are 30.5" tires. i am on a carb'd old 4.2 and i can run way over 80. the wife's 93 would bury the needle on the speedometer.

how hard is the jeep working to run in 4th gear on the highway? where do you live, which state? i know my dad's 89 wrangler with 6 cylinder never had any problems on 30s and he drove it all over hte east coast while he was stationed at camp lejuene so i cannot see 31s making that much of a difference.

if your in texas, there are lots of us who can help you out all over hte state. but, if you want to know your gear ratio, lay under the jeep and check the metal tag on the diff cover. if no tag, jack up one axle (with the jeep in neutral) and then lay under the jeep and turn the driveshaft. while turning, count how many revolutions of the driveshaft it takes to make the wheels turn one revolution. turn the driveshaft by hand.

 

[Triggersights]

The jeep doesn't seem to be rpm'd out in 4th gear on the hiway pulling an empty little flabed, but it definately bogs down in 5th. Its not really an issue if I'm not pulling, other than I can only top out at 75 or 80.

 

[Triggersights]

I'll try and get under it tomorrow if its not 2 degrees!

 

[Red Mutt Ranch]

Well it sounds like it is time to re-gear to 4:11's
Sorry buddy jeeps were never built to drive 70 or 80 MPH. My top speed ever in my CJ5 is 65 MPH. But if you do want to get it up to that speed you are going to need to re-gear them diffs.

 

[tjlboise]

I have 31's on my YJ 2.5 4 cyl, and have no problem getting up to 70. She does great. The only time I really slow down a bit is on a long hill, and it still doesn't slow down too much. I think the gearing is definitely the key.