Bigger Tires/Gearing/Transmission Wear?

jmark · **Posted:** Mon Oct 10, 2011 10:55 pm

Hey all,

I know this probably a redundant question, but i recently upgraded from 235/70/16 to 245/75/16 and notice the usual 3mph difference in the speedo as well as the RPM drop.

My concern is namely in the transmission, will any of this shorten the life of it? I'm running 3.73 gears and really want to avoid the time, hassle and expense of re-gearing.

Also, how many people have KM2s and how do you guys like them? they are a bit loud (at least to me) but darn, i cant beat the looks or the traction.

Pic:

Jeep after new tires and wheels by Jmark2009, on Flickr

XJMA · **Posted:** Tue Oct 18, 2011 4:45 pm

you'll heat the transmission up more so change the fluid more frequently and add a larger aux cooler and that will keep it alive.

805gregg · **Posted:** Tue Oct 18, 2011 9:14 pm

I was told by my very experienced trans guy to keep it out of overdrive unless on the freeway, you don't want it to lock up. My 2000 Dodge 2500 is driven like this working hard in construction and has 320,000 miles on the origional trans.

tommudd · **Posted:** Tue Oct 18, 2011 9:47 pm

Even with the 4.10s in mine I still don't use overdrive unless I'm on the freeway or over 55-60 at least
runs better and cooler I think, keeps it more in that sweet spot

jmark · **Posted:** Tue Oct 18, 2011 9:59 pm

For the most part i dont usually get into overdrive driving day-to-day around here (lucky to break 35), however when im out on the highway, thats a different story.

I'm going to get the B&M trans cooler installed before the snow starts flying. Also if i feel the trans is shifting more than it should, i typically knock it out of o/d.

Next jeep will be a manual, im tired of worrying about the automatic constantly.

tommudd · **Posted:** Tue Oct 18, 2011 10:20 pm

worrying about it all the time ?
I don't at all, just keep fluids changed like you should and run it, 165,000 on mine with zero problems

USAFCOP · **Posted:** Tue Oct 18, 2011 11:02 pm

why worry about it, as said add a cooler and be done with it. if you keep od off when below 45/50 mph you will be fine.

I have KM2s and I don't find them loud at all. actually I find them much quieter than my old MTRs. I love how they have been on and off road. we will see how they work in snow soon. in a dusting and a little slick they were fine, but it wasn't much snow.

tjkj2002 · **Posted:** Tue Oct 18, 2011 11:24 pm

805gregg wrote:

I was told by my very experienced trans guy to keep it out of overdrive unless on the freeway, you don't want it to lock up. My 2000 Dodge 2500 is driven like this working hard in construction and has 320,000 miles on the origional trans.

The TC will lock up in 3rd gear also,not just in OD.

XJMA · **Posted:** Wed Oct 19, 2011 9:41 am

it's not the lockup of the TC that is bad....it's the shifting into OD that creates a ton of extra heat when you're not going fast enough for it!! So keeping it out of OD is not a bad idea.

I'm not as familiar with the KJ tranny as I am with the AW4 in the XJs but I know that when you change tires/gearing - if you change the speedo gear so that the speedometer reads correctly it helps the tranny shift correctly. Now I know the speed sensor on the KJ is on the diff and so maybe this isn't as easy of a job, just bringing that into the discussion. when the tranny shifts where it's supposed to, it creates less heat.

heat is the enemy of all automajic transmissions!! Keep it cool (and don't sink it) and it should last plently long.

tjkj2002 · **Posted:** Wed Oct 19, 2011 8:15 pm

XJMA wrote:

it's not the lockup of the TC that is bad....it's the shifting into OD that creates a ton of extra heat when you're not going fast enough for it!! So keeping it out of OD is not a bad idea.

.

It's not the OD that is the issue either,partly.The whole issue is not locking up from lack of power to maintain speed.TC not locked up means slippage in the TC which equals heat,TC locked means no slippage which equals less heat.

dieselenthusiast · **Posted:** Sun Oct 23, 2011 10:41 pm

You may want to consider the PML aluminum trany pan. It only holds an additional 1 quart, but maybe the aluminum pan with cooling fins may help with cooling. You can also do a drain and fill without having to drop the pan.

Here’s the link:
viewtopic.php?p=377197

Bigger Tires/Gearing/Transmission Wear?

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