Eric,


Thanks for your patience b/c I know different variations of this question exist all over this great site, but I have a read a ton of info the last couple of days and am a little confused (very much a novice when it comes to Duramax/Diesel).


My one goal is to get a bigger tire on my new HD, without damaging the tranny or anything else. I don't do much trailer-pulling and am not dead-set on getting more power, I just like the look of a bigger tire. The dealership said that even changing the width of the tire will cause all kinds of computer problems.


I was planning on BFG 285's (or 265/75/16's if necessary- I was hoping to use my stock wheels). An after-market place in my town said that we could rotate the front torsion bars a couple of times- throw on the 285s- and a hypertech? programmer to calibrate speedo, etc? What would you recommend for a guy who just wants to go a little bigger but not do any damage- and hopefully not void the warranty? Thanks.

You can do that exactly....I have 285 ..and cranked the bars up 3 turns....have a Attitude and changed the speedo cal.....truck kicks butt....but it will limp the trans... hope this helps...racer

Coyete...changing tire size can get the dealer excited.. They can give you grief about it, as it confuses the puters on board. I and many others have 285's on stock rims with no problems other then the speedo off. the tranny will shift different but it will still work. The allison upshifts are based on output shaft speed, not vehicle speed.You can use a Predater or Quad to recalibrate the speedo. I think Hypertech does it also. GM cannot change the tire size for your speedo no matter who tells you anything. The attitude will change size and display corrected reading only on the attidude, it will not change your dash speedo. A few twists of the bar might be needed for clearance is all.


Hey Glenn, we can fix that limping tranny, just takes a quick trip up to Grand Rapids.... Trans go to the rescue!

Eric

Thanks for the replies- huge help!

Eric,


I have changed the tires to 285/75/16. Tire rubs on driver side when backing and turning to the left. Will adjusting the T. bars eliminate this? What fix can be done to the tranny?


Thanks,


Jon

Hammer, the reason it rubs on the driver side inner fender is that the emergency brake cable actually pushes the inner finder towards the tire. Just take a heavy duty tie wrap and pull the cable back the the body mount right behind the inner fender. No more scrubbing if you do this procedure.


I went as far as to drilling a smaller hole in the inner fender and pulling the fender to the cable with a smaller tie wrap. I hope this works for you. I also cranked the tortion bars abit.


Duramax

Thanks for the reply Duramax. I will give it a try this weekend!


Jon

Hammer u need 2 of the ties and also tie the left front inner forward.


The windshield washer tank is the problem.


I drill 2 1/4" holes in the front and 2 in the back inner fender and tie them out of the way.


03 and up have the windshield washer tank trouble.

The windshield washer tank is the problem.


03 and up have the windshield washer tank trouble.





The part of the windshield tank that hits the tire is a tab that the inner fender mounts to. If the tire will contact the washer tank, then it will also contact the inner fender at that same location. I cut the inner fender up to the tank, then there was no reason for the tab on the washer tank, so I cut that off as well. No problems running 35" tires with NO lift. I even lowered it a bit to get better CV joint and tie-rod angles. I think it would rub off-road, but I have a Jeep for that. On the street, dirt roads or otherwise it works great.