97 TJ w2.5L Throw me some ideas

[SAMSET]

sup all. im dragging my TJ on to because i dont really trust other sites. so if anyone has or knows someone that has been down this road, chime in.

Picked up this 97 TJ 2.5L on a trade. well the jeep is fine and all except its speed is topping out at about 50mph.
so it has a 2.5 5sp with 150k on the clock. 33s and stock 4.10 gears. heading down the highway in 4th i hit 50 kick up to 5th and i drop to 45. pedal to the metal im getting nothing more out of it.

things ive done so far. it had nothing but a resonator on top of the throttle body. no air filter system at all. took it all off and cleaned the hell out of the throttle body. slapped a cai style air filter directly on the throttle body. cut the cat off thinking it might have been plugged up. currently running straight pipe. new plugs, wires, rotor, cap. put sea foam in the oil,gas, and vacuum systems. did a compression test and pulled #1=160 #2=160 #3=175 #4=175.
all done, take it on the road, no change what so ever.

now i know that the 2.5 running 33s on stock gears is going to be a dog but 50mph?!? i should be able to get more out of it than that right?

obviously i know there are other options as far as motor swaps, gears, etc. but im trying to keep the budget down on this. basically the trade i had was worth about $1500 therefor this is a $1500 jeep and im not trying to drop 5k on an LS swap. i may think about gears but how much is that going to get me. spend a grand on gears so i can go 60 instead of 50?
suggestions?

 

[SAMSET]

Picks for viewing entertainment

 

[lawsoncl]

I had a 1995 YJ Hardtop with 4.10s on 30s with a couple inches of body lift It struggled to hold 75 and only did 45 in 4th going over the passes. You've got it worst with no top, more lift, and even bigger tires. HP peak on that engine is around 5200 rpm so 5th gear going to be mostly unusable.

 

[cabjeepster]

May be a dumb question but, are you sure it has 4.10 gears?

 

[MKR5150]

4.10s and 33s is the issue. Regear to 4.88s should help

 

[need-a-bow]

May be a dumb question but, are you sure it has 4.10 gears?

4.10s came standard in the I-4 XJs and TJs. Only way he'd have 3.55s or higher would be if someone swapped them.out beforehand, which is possible

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[POLAR_JEEP_04]

My 2.5L 5 speed YJ with 4.10’s has the same issue with 31”s. I would put my money on you needing lower gears too.

 

[DoWorkXJ]

Gears.

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[lawsoncl]

Crunching some quick numbers I came up with 1800rpm in 5th gear at 50 mph which is about 50Hp at the engine and maybe 45 to the wheels. 2100rpm in 4th isn't much better. You're lugging an engine that's already a bit anemic

 

[trippled]

Have you checked the speedo accuracy? I wonder if you're actually going a bit faster than you think.

 

[lawsoncl]

A bit of google give a bunch of people saying:

"4) you can switch to an electric cooling fan. Remove your fan clutch and blade and install a thermostat controlled electric fan which will lighten up the drag/load on your 2.5L and free up 10-12 HP. A ford Taurus fan swap is the most popular swap with very little modifications to install."

I can see 10-HP at higher rpm, maybe not so much at 2000-rpm.

 

[SAMSET]

The tag on the D35 says 4.10 so unless they’ve been swapped I’m guess they are.
I have read about the taurus fan swap. Was thinking I could do that.
The biggest problem I have with doing gears is I’m not trying to do a gear swap running this D35. Axle swap is not in the budget for a while. May have to just deal with it until I can do that axel swap I guess.

Other thought are picking up a 4.0 xj for >$500 and pulling the entire drive train and rear axle. But that is a larger job than my garage and skill level bring lm assuming new computer. New wire harness etc

 

[Jeep Driver]

You've got the perfect candidate for a SBC.

 

[POLAR_JEEP_04]

LS swap time

 

[Ghost]

I'd find a TJ guy with an 8.8 already upgraded and bolt it in. Then just re-gear the front to match. Or a TJ rear 44 from someone upgrading. Or you could get an 8.8 and assemble the parts to put it in and take you time and spend money as you have it. Either way you need deeper gears or more motor. I had a 97 2.5 with the auto and it was gutless. I can only imagine what that one is like. GL!

 

[Snipes243]

Dumb question but have you checked the speed compared to an god unit?

I thought my 97 2.5l with 33 wouldn't go above 65. But the speedo was off cause we used 2 different gps units, and it was actually going 75mph.

 

[PhotographerMike]

Agreed, my 1996 2.5L, manual trans XJ came with 4.11 gearing. With "oversize" 235 / 75 R15 Firestone Destination A/T tires my GPS and speedometer both read the same at 65.

I thought my 97 2.5l with 33 wouldn't go above 65. But the speedo was off cause we used 2 different gps units, and it was actually going 75mph.

 

[WB9YZU]

I had a YJ with a stock drive train (D30/35, 4.10, 2.5L) and 33X12.5s, it went 65 on the flats, but I would need to down shift to 3th to make hills. I was almost never able to drive in 5th. A re-gear would have certainly helped.

The nice thing about a 2.5L with a manual and stock drive train is you will never blowup a decent u-joint, even if you try real hard. It will run out of torque before you can do any damage

 

[Ghost]

I had a YJ with a stock drive train (D30/35, 4.10, 2.5L) and 33X12.5s, it went 65 on the flats, but I would need to down shift to 3th to make hills. I was almost never able to drive in 5th. A re-gear would have certainly helped.

The nice thing about a 2.5L with a manual and stock drive train is you will never blowup a decent u-joint, even if you try real hard. It will run out of torque before you can do any damage

I cannot tell you the number of joints I broke with my 84 xj with a 94 yj drivetrain on 33's. I also broke the D35 with it and then spun the d35 housing. Of course I was and always have been hard on the xj's in the rocks......

 

[WB9YZU]

WOW! I guess!

Goes to show you YMMV

Both the XJ and YJ had 260 joints.

Personally I think 270 joints with the larger factory shafts were an issue. The ears on those shafts are weak. You never actually break the joint until you chuck a cap, then all he!! breaks loose.