98 4.0 struggling up hill

[Jeepoftheseus]

Hey folks, as many of you know I'm brand new to jeeps and manual transmissions for that matter. I took a drive from Phoenix to Payson yesterday and I'm finding that the TJ can't really get past 71mph on a 6% grade. Is this a skill issue or could it be something like the Gearing or even fuel delivery? I know that the PO put an auto-locker in the back but there are only 31 inch tires on it so I imagine it's stock Gearing. Any perspective that will help me think about this is welcome.

 

[tworley]

6% grade? Even the newest of vehicles can struggle on something that steep.

 

[nk24]

I agree with @tworley. Being able to hold 71 mph going up those climbs on the Beeline is pretty solid. I remember when I had my 2000 TJ with the 5 speed that I would drop it into 3rd gear and try to maintain 60 mph, though I had 33" tires with 3.73 gearing.

 

[TheBoogieman]

3.07 gearing?

 

[Jeepoftheseus]

3.07 gearing?

3.73 rear axle

 

[tr21triton]

3.07 gearing?

If he had that he'd be in 4LO to get to the top.

 

[Brianj5600]

I thought altitude was an issue, but Payson is not much above sea level. What RPM was it spinning?

 

[APC]

That's what about to expect. My 97 TJ 4.0L 5sp has the 3.07 gearing. I'm in 3rd gear on most grades..

 

[JKP]

Hey folks, as many of you know I'm brand new to jeeps and manual transmissions for that matter. I took a drive from Phoenix to Payson yesterday and I'm finding that the TJ can't really get past 71mph on a 6% grade. Is this a skill issue or could it be something like the Gearing or even fuel delivery? I know that the PO put an auto-locker in the back but there are only 31 inch tires on it so I imagine it's stock Gearing. Any perspective that will help me think about this is welcome.

So, are you in 5th gear or have you downshifted to 4th?

 

[KennethS]

I thought altitude was an issue, but Payson is not much above sea level. What RPM was it spinning?

What? Payson is 5003 feet above sea level.

Good call on the RPM, though.

So, are you in 5th gear or have you downshifted to 4th?

On the first couple trips to Payson in my 98 (3.73 gears, 32" tires) some of those climbs resulted in me having the gas pedal on the floor and the Jeep was slowing down. That really shocked me, wide open throttle and the RPMs were decreasing! I eventually discovered that downshifting and keeping the RPM above 2700 let me accelerate up those hills, and I actually got better mileage that way. Seems counter intuitive, but having the engine above 2700 RPM really worked well.

 

[JKP]

What? Payson is 5003 feet above sea level.

Good call on the RPM, though.



On the first couple trips to Payson in my 98 (3.73 gears, 32" tires) some of those climbs resulted in me having the gas pedal on the floor and the Jeep was slowing down. That really shocked me, wide open throttle and the RPMs were decreasing! I eventually discovered that downshifting and keeping the RPM above 2700 let me accelerate up those hills, and I actually got better mileage that way. Seems counter intuitive, but having the engine above 2700 RPM really worked well.

You want to keep it around the peak torque. On my TJ and YJ, the torque peak occurs when the tach needle is close to vertical. It changes based on the various intake and exh manifolds and heads used on the 4.0s.
92 YJ peak torque is 220 lb ft @ 4000 RPM
06 TJ peak torque is 235 lb ft @ 3200 RPM

 

[Brianj5600]

I did not notice that the altitude was shown in meters on the quick search

I should have known after seeing the towns home page. The picture looks beautiful.

 

[Painfultruth]

Hey folks, as many of you know I'm brand new to jeeps and manual transmissions for that matter. I took a drive from Phoenix to Payson yesterday and I'm finding that the TJ can't really get past 71mph on a 6% grade. Is this a skill issue or could it be something like the Gearing or even fuel delivery? I know that the PO put an auto-locker in the back but there are only 31 inch tires on it so I imagine it's stock Gearing. Any perspective that will help me think about this is welcome.

Put a Turbo on it.

 

[Zorba]

Vehicles slow down on hills...

 

[ColoJeep]

Vehicles slow down on hills...

Some more than others .

 

[KennethS]

Put a Turbo on it.

Word. One of my other vehicles is turbocharged / intercooled and I don’t need to downshift on the climbs going to Payson. Kinda cool maintaining speed in 6th gear with cruise control on during those uphill climbs.

 

[DaveC]

It's a brick on wheels..... going uphill.... steeply..... in the mountains.... I'll take 71 mph going up the Beeline in a stock geared TJ on 31s all day, all night, and twice on Sunday.

 

[machoheadgames]

What gear are you going uphill in?

 

[TheBoogieman]

Vehicles slow down on hills...

That depends on if the hill is up or down. I only go downhill to make my MPG's better and my Jeep seems really fast.

 

[Jeepoftheseus]

Thanks everybody, it sounds like the only thing that needs fixing are my expectations