97 TJ 2.5L performance parts

hey all,

Last week purchased a 1997 Wrangler SE (2.5L), automatic transmission. It has large 32" tires and lift kit. Nice looking but performance is poor. If I could eek-out another

10-15 horsepower it would be much more drivable around town and on the highway. My questions are: Does anyone have experience with performance mods; air-intake, exhaust, etc. for the 2.5L 4cylinder?

Also, how can I tell what gear ratios I have? Judging from the performance with the 32"'s I'm guessing I have the stock Dana 35's. ... ( 0-60 in about 5 minutes on flat ground. No chance of even hitting 60 on a hill :)

Any opinions on reputable/reliable JEEP performance parts places?

I have no books or documentation on my JEEP yet but I am learning about it by trial and error! Any help would be appreciated. Someday I will be able to give back!

TJ

Reply to
hammertc2000
Loading thread data ...

Put the stock tires back on it, and get rid of the auto.

Earle

Reply to
Earle Horton

Yes, I guess your right, getting rid of the auto trans and the 32's would improve performance :) Unfortunately, getting rid of the auto trans is not an option as I only have one leg to drive with. As for the tires...well...I'd like to keep them. So any performance minor mods available while still keeping the auto and 32's?

Thanks, TJ

Reply to
hammertc2000

Cat-back exhaust and 4.0 liter throttle body won't set you back much, especially since exhaust doesn't last forever. I found on mine that the mileage improved more than the power from engine mods. What you really need to do is regear the axles.

Earle

Reply to
Earle Horton

And the re-gearing will run $400-$500 for parts and that same amount for labor.

None of the other 'bolt-on" products will get you the necessary power out of the 2.5 liter engine.

Your differentials should have a tag that shows the gear ratio, if not you can get a "Build Sheet" from your corner DC dealership... all you need to provide them is the Jeep VIN number.

Build Sheet:

formatting link

Axle ID and Gear Charts

formatting link
Once you know your stock gear ratio there are charts to point out the appropriate new ratio given your new tire size to regain 'stock' performance.

Reply to
billy ray

Good point about the exhaust. Better gas mileage wouldn't hurt either. Worth the try at least. Regearing the axles does make the most sense. I just need to figure out what I have and how to change them. I'm not looking for much performance gain.

Thank you for your advise. I much appreciated it. TJ

Reply to
hammertc2000

Charts

formatting link

Very cool. Good info. Thank you! TJ

Reply to
hammertc2000

Normally the 2.5L engine with a manual will be geared at 4.10's, but I guess they may have 3.07's with the automatic (the auto 4.0L does). You would want to get at least 4.10 gears. If you already have 4.10 gears, consider 4.56.

Your transmission doesn't have an overdrive, so after you regear get used to your tach being at around 3000RPM at highway speeds and your gas mileage going south.

You'll also need to replace your speedometer sender gear with >> ...> Yes, I guess your right, getting rid of the auto trans and the 32's

Reply to
Matt Macchiarolo

Reply to
philthy

Reply to
L.W. (Bill) Hughes III

You have 4.10 gearing. 4.56 will return some performance and gas mileage. Get the 4.56 gears, cat-back and 4.0 throttle body, and be happy.

FWIW, my 89 YJ 2.5L pushed my 33's around town and on the highway with no problems, but it was a five speed. The 2.5L is a great engine.

HTH

Carl

Reply to
Carl S

I requested a build sheet from DaimlerChrysler. This should help.

In the meantime, I looked today at the rear differential cover. It definately has Dana on it. Also, it is a small metal tag with stamped numbers:

52111763 3 73 5957
Reply to
hammertc2000
4.10 is your gear ratio.

Carl

Reply to
Carl S

You can just jack up one wheel and turn it twice while counting the number of turns the driveshaft turns. Marking both the driveshaft and wheel with chalk helps count.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06
formatting link
(More Off Road album links at bottom of the view page)
Reply to
Mike Romain

You could look at the build sheet, or crawl under and look at the tags on the differentials.

However, to be sure, you have to roll it one turn of the tires while counting revolutions on the driveshaft, if someone has possibly modified it.

Reply to
Richard J Kinch

Ok. I jacked one wheel and mark both the driveshaft and the tire. I rotated the tire (2) revs and the drive shaft rotated almost, not quite, (4) times. I'd say 3.75. I'm guessing my gear ratio is

3.73. I think this is what I saw stamped on the tag on the real differential. I'm still waiting for a response from DC on the build sheet. Looks like a 4.5 R&P is in my future....
Reply to
hammertc2000

That is an unusual ratio for a 4 banger as far as I know, but you are right about the tag. I thought they were 4.11 or more, but that is only from what I have seen posted.

I think I would be checking the front axle out to make sure it is the same ratio as the rear with the thought someone might have swapped in a new rear end for some reason.

Your gas mileage and perceived power are low also due to the speedo being off by 10%. When you finally decide on what ratio you want, it is easy to swap the speedo gear for the correct one.

As far as power goes, intake and exhaust usually help. I know on the older Jeeps, a better coil also helped. I don't know if a higher voltage coil like an Accel will help the 4 or not.

I also have seen 4's with electric fans instead of the belt driven ones. Apparently the increased alternator load is slightly lower than the fan belt load so you come out ahead power wise. It will wear out the alternator slightly earlier but...

Where we used wheel is over an hour's highway run away and I have driven to the pit and wheeled all day with groups of other Jeeps only to find out a couple have been 4 bangers. I had no idea until hoods got opened that they had the small engine in them. Their performance on the trail or in the mud sure didn't suffer.

The automatics have issues with not staying in the gear they are 'told' to stay in. This is a big disadvantage when climbing sand pit or ravine walls. They do great in 2nd gear, but then decide to drop to 1st, which spins the tires and digs holes so that's as far as they go.

There are kits to keep them in the gear you want I believe. I am not sure if this works on all of them or not. Maybe Bill still has the link to that, my link is dead.

Mike

Reply to
Mike Romain

The 3.73 gears are to make up for the torque converter slippage, I think. The electric fan in mine "never" comes on while the vehicle is moving. Even in city driving or off road, 5 mph is enough to cool the engine. That is why you get an electric fan. Of course, it is all wasted if you don't set the thermostatic fan control properly. You can't blame the manufacturer for that. They do include proper instructions.

Earle

Reply to
Earle Horton

You got 4.10 with an auto and 3.73 with a stick with a 4 banger in '97.

Reply to
Scott in Baltimore

??? This is backwards from pretty much every other year then.

Scott >> The 3.73 gears are to make up for the torque converter slippage, I think.

Reply to
The Merg

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.