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Cant get over 55mph

3K views 20 replies 11 participants last post by  mukluk 
#1 ·
I'm BRAND new to Jeep's! Just bought a 97 Jeep TJ, had the fuel pump replaced & exhaust leak fixed. Before I got it fixed when I'd push hard on the gas it'd bog down, the fuel pump was the problem and it no longer does that. I still can't get it to go past 55mph for some reason! I'll get it up to 55 in 4th gear and when I shift to 5th it just stays at 55 and SOMETIMES barely gets up to 55. Here is what I have...

97 Wrangler TJ
168k miles
2.5L, 4cyl, 5 speed manual
4" rough country lift
33.12.5" Cooper Discoverer tires on 15" ion alloy wheels
Newer injectors, u-joints, tie rods & ball joints
New transfer case
 
#8 ·
With a 4 cyl 5 speed, a lift and 33's you can forget about 5th gear. If you have stock gears that's your problem. My 4 cyl with 4:88's would go 70 in fourth but I was really turning it hard. I rarely went over 65 in it.

Put some gears in it and it will go a little faster. If you don't like that I would go find a 6 cyl.


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#9 ·
With a 4 cyl 5 speed, a lift and 33's you can forget about 5th gear. If you have stock gears that's your problem. My 4 cyl with 4:88's would go 70 in fourth but I was really turning it hard. I rarely went over 65 in it.

Put some gears in it and it will go a little faster. If you don't like that I would go find a 6 cyl.
Agree. And even a 6 cyl may not cut it. When I put 31's on my '93 4.0L I couldn't go over 60mph in 5th gear. I had to change the factory 3.07 gears to 3.73. That brought everything back to where it should be.
 
#10 ·
A 4 cylinder with stock gearing and 33's needs to have the rpms up to 3500 or higher to maintain speed before you shift IMO. I'd shoot for 4000 rpms and leave it in 4th.
 
#14 ·
finding a place that actually knows what they are doing is probably harder.... hahaha... I' have done enough gearing in my span of working in shops and i tell yea i wouldnt even do it myself (shop had proper tools i don't lol)

but depending were you are.. ive seen it go in to 2+k and as cheap as 1200 canadian with good 4x4 shops having deals.. but regearing to atleast 4:88 would put you close to stock ratio's..

my first 98 4 banger was on 33's and 4:88 35's and 4:88 and 235/75/15(tearing it up lol) haha and it makes a world of difference..

my second was stock gearing on 31's and it was a dog... swapped the axles from the first jeep over and setup some 32's... it was great .. for the 8 hours i got before i blew a piston skirt and was parked for a month.. good o'l 4 bangers..
 
#15 ·
If you are looking for a commuter or something you're going to put a lot of highway miles on and keep the 33 inch tires it would be far cheaper to sell the four-cylinder jeep and go find a good six cylinder. If it's a second vehicle you are going to use to just hunt or play in the four-cylinder is great just read gear it.




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#18 ·
So regardless of the gears in the axle, you should still be able to get to 70mph. If you have numerical low gears, you can just use a lower transmission gear to get there. Is it possible the catalytic converter is plugged up?

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You have obviously never had a 4 cyl jeep! You are missing two things. You can only spin a motor so high without breaking something and a jeep is the aerodynamic equivalent of a cinder block.

With all the mods available including a throttle body from a 6 cyl plus 4:88's my jeep struggled to hold 70 in 4th gear. Any hill and you were loosing ground. That was with 33 inch Baja claws.

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#17 ·
When I first got my 5 speed TJ 4.0 I thought there was something wrong with it because I couldn't maintain speed in 5th gear. I have 33's and a 2 inch OME lift. I noticed the speedometer was off about 7 mph low. After getting on here and getting some advice I decided to give myself a chance to get used to the Jeep's sounds and experiment with shifting points etc. I found it was me not the Jeep. Now I only use 5th for highway cruising and keep to 4th in everyday driving. My Jeep likes to be above 2k for up-shifting and I downshift around 1500. For running in 5th I take it around 2500-3000 before making the shift. According to my GPS that's about 60mph. I say give yourself time to learn this particular Jeep before spending a bundle on it.
 
#21 ·
A four banger with stock gearing and 33" tires should be able to go faster than 55mph in 4th gear. If it can't, either something is wrong with the Jeep or you have it so overloaded with equipment and armour that you may as well drag an anchor behind you.
 
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