80mph max speed?

jafstl38 · **Posted:** Thu Apr 29, 2010 11:26 am

I've been getting pretty frustrated with my KJ lately, I've had a new tranny put in and it still acts like it's just dead, it has power through 1st gear and nothing after that, my ford ranger with 200k on it had more power. Was on the highway and buried the pedal and could only hit 80 for fear the motor would blow. I anyone elses KJ this doggy? Has Frankenlift with 245/75/R16s

Twack · **Joined:** Fri Mar 19, 2010 1:05 pm **Posts:** 40

gas or diesel, if diesel it sounds like a dead turbo or something along those lines

jafstl38 · **Posted:** Thu Apr 29, 2010 11:36 am

Sorry it's a gas 3.7l, I'd love the 2.8 though

bmrrwolfe · **Joined:** Fri Dec 11, 2009 4:24 pm **Posts:** 132

Humm...
I usually hit 80 on a near daily basis with plenty of pedal left, granted i do not have a lift, but i do have armor, rack, brush guard 245/70s and other weight added.
Does the tranny shift alright and when at 75-80 what RPM are you at?

InCommando · **Posted:** Thu Apr 29, 2010 2:23 pm

Wow. The power in the lower gears is a frustrating factor. Plugged cats or something can rob power, but this...

For comparison mine will do 111 mph on 245/75/16's and I usually cruise at 80-85 with no issues.

Twack · **Joined:** Fri Mar 19, 2010 1:05 pm **Posts:** 40

i know for a fact that the speed is limited on an 2002 gasser is between 110 and 115. Never had a problem getting it up to that speed. Not a fan of that speed with my lift and tires now but way back when.......

jafstl38 · **Posted:** Thu Apr 29, 2010 2:25 pm

111!? I needed a downhill run w/ the wind blowing me downhill to hit 80! Ive been thinking its a clogged cat, my exhaust does pop alot like a exhaust leak but I have no check engine light?

JeepinJarhead03 · **Posted:** Thu Apr 29, 2010 2:55 pm

naturally i have to say first, that wide open isn't the best way to get our vehicles to accel past 60, but with moderate steady gas you shouldn't be having problems going over 80 unless somethings dragging you

if it's popping it's possible it's the cats, a clogged or dirty airfilter will also make it drag booty

last time you changed/cleaned airfilter?
last time you changed plugs?

was the wind blowing 50mph in your face? coming back from my ohio trip coming through WVa the wind was keeping me from going over 60 half the time, and pushing me like a sailboat the other half of the time

the 3.7 isn't a dog if it's taken care of, you've got something going on

jafstl38 · **Posted:** Thu Apr 29, 2010 8:50 pm

I noticed today if I hit my overdrive off it does great, I could hit 90 easy. But with overdrive on it's a dog! I have a brand new KN drop in filter in, I don't know about the plugs though

tjkj2002 · **Posted:** Thu Apr 29, 2010 9:56 pm

jafstl38 wrote:

I noticed today if I hit my overdrive off it does great, I could hit 90 easy. But with overdrive on it's a dog! I have a brand new KN drop in filter in, I don't know about the plugs though

Was it a brand new trans or a remaned/rebuilt/used?

jafstl38 · **Posted:** Thu Apr 29, 2010 10:03 pm

It was a used tranny with 30k on it

tjkj2002 · **Posted:** Thu Apr 29, 2010 10:09 pm

jafstl38 wrote:

It was a used tranny with 30k on it

Then it is bad or you need to have it flashed.You never know the condition of a used trans,even low mileage ones as you do not know how they ended up in a junkyard.Accident vehicles are the worst donors for parts like a trans since if the accident was bad enough to total the vehicle(talking about newer vehicles only) then it could have been bad enough to cause unseen driveline damage.

Hope it has a warranty.

jafstl38 · **Posted:** Thu Apr 29, 2010 11:24 pm

God I hope its not a bad one, I did have a pinion/shift point reset on it about a month ago but they reset it to 677 revs and Im not sure if thats right for 245/75/R16 tires. It acts perfect if i have O/D off, it just seems to always shift down into overdrive and stay there

JeepinJarhead03 · **Posted:** Thu Apr 29, 2010 11:42 pm

may just need a relearn or a learning tune

jafstl38 · **Posted:** Thu Apr 29, 2010 11:46 pm

Im guessing only a Dealer can do this?

JeepinJarhead03 · **Posted:** Thu Apr 29, 2010 11:54 pm

or an experienced and equipped transmission shop

jafstl38 · **Posted:** Fri Apr 30, 2010 2:28 am

Hmm Im gonna have to look into this because if I have to replace my tranny again its gonna be Bye-bye KJ..

jafstl38 · **Posted:** Mon May 03, 2010 1:13 pm

I had to fellow jeep owners, not kjs they have Tjs, look at my lagging power issue and they maintain that I just need to regear it to 4.10s, I know this would help but arent alot of people running 245s with stock gears still? its not a huge tire?

long_tall_texan · **Posted:** Mon May 03, 2010 1:39 pm

Gears would help, but that is very secondary to some other problem. I am running 32x11.50x15 BFG All Terrains with my stock 3.73 gears. I do not have any trouble getting up to speed. Only issue I have is in hilly terrain, it shifts between 3rd and 4th a lot. I can accelerate up to any speed that a stock KJ could. You have some other issue. I would start with checking the cats. Decreased exhaust flow could easily cause this...

jafstl38 · **Posted:** Mon May 03, 2010 2:14 pm

What's the best way to check my cats? Pull the o2 sensor and see if it runs normal?

80mph max speed?

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