on late motel SUV\'s, can you really burn up your transmission if you put larger tires?

well i got a brand new sport trac, and i was wondering if its true if you put larger tires on there, you can burn up your transmission because your screwing with shift points and etc. i know for sure it'll screw up with your shift points.

but is there really any harm in going with larger tires. i'm only buying new tires because of the snow here in utah. so these tires will only be on during the snow season. then right back off in the spring and summer.

what size of tires do you think i could fit under there safely? right now they have 235/70/16. looks like i could possible fit another inch or two tires. don't know for sure cuz i don't know how close it is when i'm at full steer.

please give feedback!!!
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Where does this stuff come from? Then again, it's possible I misunderstood the question? If you are changing (to the same size, larger or smaller) wheel/tires on both axels, there is no problem, just as long as all the tires have the same roll out. There is some amount of variance allowed...I would think it would need to be less than a 1/2 inch.

There is a potential problem, if you put radically mismatched tire or wheel sizes on side to side or front to rear axels, especailly on hard surface improved roads, if you have all-time or engage 4 wheel drive the rdifference in rotation may be enough cause the differential to to engage constantly.

Sometimes, for dirt, sand, bog or mud racing, the competitors will purposely install high/lower gears in the front axel to compensate for having larger tires (or want to over drive one axel compared to the other).

Since so many of the modern SUV's are based on automotive platforms, instead of actual trucks, there may be other considerations at play. Begining with the obvious, there must be a practical limit to how large, heavy a tire/wheel combo you can slide under one to these..even with a lift kit.

<font size=-1>[ This Message was edited by: Beoweolf on 9/24/04 9:48am ]</font>

When changing to a different size tire, it will throw the shift points and speedo off but this is nothing that cant be reconfigured in the GEM module easily at any Ford dealer. On a side note, if you go a lot bigger on tallness, you damn sure wont prolong the life of the trans.....which might I add seems to do kindof a piss poor job in those vehicles anyways.

i was liking the size of 31.5x10x5x16 tires. how much do you think it cost to re-program the transmission at ford? think if i don't do that it'll do alot of damage?

if it will cause some damage or cost alot to re program it, i might as well stay with the stock 29 inch tires.


oh yea, the original tires are about 28.96 tall, so will a 2.5 more inches do any harm?

It shouldnt cost anymore than 1 hr labor. The downside to not doing this is late shifts and a slow speedo (which could work to your advantage due to keeping miles low). However, I dont think recalibrating is going to help prolong it either. The only thing that bigger tires could do is add a little extra stress to an already (in my opinion) already stressed out trans. The trans could stand to be beffed up a little more going into that heavy of an SUV from factory.

I would just spend 350 and get me a Hypertech programmer.Allows you to adjust tire size,shift points,top speed limiter,and other things.Then you can even switch back to your stock settings.
Bob
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I will lend my proffesional opinion on this one and say yes it does cause some extra wear and tear. Seen many a CHEAP(get it Jeep) grand cherokee AWD come in with the wrong size tires with scolding hot frt and rear difs(starting to sieze up) and guess what that does to your transmission. On non AWD that remain on all the time vehicles this would be less of a concern but however the pontential is still there. Never mismatch tires and on AWD on all the time alway replace all 4 tires at the same time to help save the life of said components. It sounds far fetched at first but once you take a hard look at the facts the evidence is there to support this left field belief. [img]/phpBB/images/smiles/icon_smile.gif[/img]

Forgot to add like mentioned before unless you have the module recalibrated for the fifferent tire size your trans will shift at the wrong time(tricking the ecm and solinoids) in some cases causing extreme wear and others minimal wear. The newer the vehicle the moer this is becoming a problem. Events have to be exact for the ecm to work in the manner it was suppose too. Good luck




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