Gears?

JL Rockies · **Posted:** Mon Aug 20, 2007 11:46 pm

I am hoping that someone smarter than I can help a brother out.
I just lifter my rig and put 32" tires on it. My problem has become very apparent on my current trip through Colorado Springs. My rig does awsome sitting in Colorado's bumper to bumper traffic, but the problem was the trip into town via I70.
There are some steep grades you have to climb and while climbing them, my revs are high but I can go no faster than 50 MPH (much to the shegrin of the locals).
I am thinking that the ratios are all out of whack with the bigger tires, I did not have the problem with the stockers. I have the 2.8 Turbo Diesel with automatic trans. my questions are:

What to I need to make everything "normal" again?

Where can I find what I need?

Who would do this kind of work?

Thank you.

KJ04 · **Posted:** Tue Aug 21, 2007 5:59 am

Did you try taking it out of over drive?

JJsTJ · **Posted:** Tue Aug 21, 2007 8:20 am

4.10 gears would help. Hit up unixxx on the forum. He has good deals for the parts you need.

Jeepjeepster · **Posted:** Tue Aug 21, 2007 8:51 am

yup, needs to be regeared to gain that lost torque back. Main reason why Ive not gotten bigger tires, we have alot of hills around here and I need my torque. Its ok if you live out where its flat, but I cant do that.

DarbyWalters · **Posted:** Tue Aug 21, 2007 9:19 am

Have you already adjusted your speed for the tire size? If your speedo reads 50 you are probably going a bit faster than that...not much I guess. The CRD should be able to keep up without any problems. ???

You might also think about upgrading your Torque Converter with the one from SunCoast. It will lock up and may keep your revs down.

JL Rockies · **Posted:** Tue Aug 21, 2007 12:28 pm

I have not tried taking it out of overdrive. I was concerned that the revs would go even higher than they already were.

The speedo is off 3 mph (verified by GPS), the speed limit on I 75 is 75mph (65 in parts) so you can understand why I was pissing people off going up these steep grades.

Is unixxx a vendor?

Who would do this kind of work, a transmission guy?
Any recommendations from my homies in the rockies?

ATXKJ · **Posted:** Tue Aug 21, 2007 2:19 pm

My CRD's made it to Colorado 4 times so far - and I've never had any problems keeping up with (or passing) traffic on mountain passes - even with 245/75/16 MTR's and F37 so I'd be concerned that there's something else happening, it doesn't seem that a 5% change in tire size should make a dramatic performance change - some yes - but not to the point that you can't run faster than 50?

GPR65 · **Posted:** Tue Aug 21, 2007 2:37 pm

i agree it shouldnt kill your power that much unless the tires are made out of lead.

DarbyWalters · **Posted:** Tue Aug 21, 2007 2:43 pm

His tires are about 10% bigger than stock...but that still should not affect a CRD like that...something else is going on here. Either a transmission problem or air in the fuel lines would be my guess

Neatus · **Posted:** Tue Aug 21, 2007 6:01 pm

ATXKJ wrote:

My CRD's made it to Colorado 4 times so far - and I've never had any problems keeping up with (or passing) traffic on mountain passes - even with 245/75/16 MTR's and F37 so I'd be concerned that there's something else happening, it doesn't seem that a 5% change in tire size should make a dramatic performance change - some yes - but not to the point that you can't run faster than 50?

I disagree, I had 245/75/16s and my gasser didn't hardly flinch at the change in tires over stock. Once I went to the 265s all engine performance went downhill. I know it isn't a torquey CRD but I would still think that any tire over 31" would degrade performance.

jason thompson · **Posted:** Tue Aug 21, 2007 6:11 pm

You need gears
while the CRD has torque the RPM range is limited and once it is maxed out then thats it
unlike a gas KJ that can pull 4500 rpm ,2nd gear and 50 mph or something like that the CRD would blow up at that RPM so it has to be in a higher gear but it has nothing more to offer

Oh all you can do is go 4.10's get the front from stealership and rear from who ever has them
find a good 4X4 shop and prepair to pay

KY Liberty · **Joined:** Sat Jul 09, 2005 1:46 pm **Posts:** 1195

Those tires are about the same weight as the 245/75R16 MTR's, but they are definately bigger in diameter. You need to go to 4.10 gears, but you might have something wrong also. I would expect going from stock to the 235/85R16 MTR's would be a big loss in power, but would expect to still be able to break 50 mph on a hill. You said you're getting high rpms, I wonder if your torque converter may be about done for?

scrambledKJ · **Posted:** Tue Aug 21, 2007 7:30 pm

I don't think that the tire change is to blame for your woes. The CRD had more torque than most any jeep I have ever owned, and I have run 37's on stock gears with an old 258. If you are going to do the gears, find a shop that does 4x4 work. 4 Wheel Parts is a good place to start. I worked for them years ago and had the joy of replacing many sets of gears set up by shadetree mechanics. Nothing like tossing a grand away after a week of driving. Expect 250-350 labor for the rear and prolly twice that for the front. I hated dropping ifs chunks to regear. make sure that whoever does it uses complete new master install kits.

Travis

KJ04 · **Posted:** Tue Aug 21, 2007 7:39 pm

I was uder the impression that the CRD comes standard with the 4:10 gears. Someone correct me if I'm wrong.

tjkj2002 · **Posted:** Tue Aug 21, 2007 7:46 pm

KJ04 wrote:

I was uder the impression that the CRD comes standard with the 4:10 gears. Someone correct me if I'm wrong.

The only KJ's that came with 4.10's are the 4 cylinder gassers.

ATXKJ · **Posted:** Tue Aug 21, 2007 8:20 pm

If the engine is revving
'my revs are high but I can go no faster '
Then you're not shifting into overdrive, with F37 I need to be about 62mph for 5th (and I think about mid 50's for 4th)- so you're above the Torque peak but it won't upshift, because the speedo isn't going fast enough

so many things on these beasts is computer controlled I'm wondering if you have to have the computer reset to the taller tires? Most folks haven't - but a couple have.

cmohr - got a significant improvement in his V6 by have the speedo adjusted for the tire size
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?t=21020

I just keep going back to when I changed from 225 to 245's the only performance impact was that I couldn't spin the tires as easily, so it doesn't seem reasonable that the next step up from 30.6 to 31.8 diameter kills performance, especially when that puts you in the middle of the torque peak on the highway.
I was running 80mph on I10 and it was happy at ~2300rpm - and one of the reasons I love the Turbo is that I don't get any change due to altitude - it adjusts.

BCool is a CRD running 235/85's - but he's in California - I wonder if he's climbed any mountain passes since his tire change?

BCool · **Posted:** Tue Aug 21, 2007 11:37 pm

yeah, I run 235 85's and you have a problem, towing a couple thousand pounds I can keep above 60 with those tires up a steep steep incline. Its not a lack of torque, I can keep 80 going to utah from vegas or vegas to nor cal and not have it downship and not have it go below 80. Its not your gears, don't listen to them, gears would throw you higher on your torque curve. This is another issue.

JL Rockies · **Posted:** Wed Aug 22, 2007 12:17 am

Thanks for the replies. I have some more data for you all. I am shifting to the "there might be something else" camp.
This morning when I got onto I 25, I had the pedal to the metal after 40 MPH the RPMs were above 3K and there was a long time to get to 50 MPH (with OD off). I was driving like the ECU was in limp mode. I pulled over, restarted and the condition continued.
I was able to cruise after a while @ 80 MPH with no probs. When a steep grade came up, I took it out of OD and the cruise control was able to maintain speed. When I would pull over to meet with a client the condition would start over again. It seems that when the tranny is cool this happens. I am staying the night in MOAB, I will let you know what happens in the morning. It's very scary to merge with traffic moving faster than 40 MPH as it is now. This was not going on when I first posted.

I do have a CEL thanks to Jiffy Lube (I think). They put the wrong oil in it (was discovered hours later), stripped the drain plug and the oil pan. The CEL appeared after. The code the Jiffy Lube guy read was p1189 which has something to do with a pressure switch I think. The CEL comes on and goes away when it wants to.

KY Liberty · **Joined:** Sat Jul 09, 2005 1:46 pm **Posts:** 1195

Code P1189 is Engine Oil Pressure (EOP) Switch Circuit. It sounds like Jiffy Lube really messed you up.

Rush345 · **Posted:** Wed Aug 22, 2007 8:55 pm

I was just looking around a Checker Auto parts and a Napa Parts store in the past 2 weeks, just killing time on both visits I heard a customer complaing about stripped drain plugs and misthreaded oil filters both done by Jiffy Lube. So to other L.O.S.T. members let the buyer beware. I think it's too coincidental that this is at least the 3rd time I have heard of Jiffy Lube screwing up someones ride.

Gears?

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