2nd Gen Non-Engine/Transmission Anybody with 315/75/16's

[Skipjack24]

I was wondering if anyone out there is running 315/75/16 with an auto and 3. 54's in the diffs? I ran this size for awhile but found cruising unloaded at 55-65mph in traffic had the engine RPM between 1450 and 1550. This is unloaded and I tended to have to shift my trans manually with the lockout button between 3rd and 4th in this configuration (as the road required).



I was just wondering if anybody else was running them and how they handled to higher speed at lower RPM's?



Thanks

 

[gwizpro]

I am running Big O 315's and they seem fine. I am of course running 4:10 gears too.



The larger tires look great, but they do drift more when driving a straight line, this is normal for a larger tire.

Also, found out that the larger tire doesn't improve traction when off road, my 305's gripped better. Yet the 315's have a more aggressive pattern.



RPM's are are about 2000 at 70, so I would say you are in line with your numbers. .



Above all else, THEY DO LOOK GREAT!!!

and I get a lot of people who look.



The RackMan

 

[FFL8N]

I have 315/75/16 on weld 16X10 rims. I also have a 6 speed instead of the auto. I have 3. 54 gears, but don't like them with the big tires. I want to switch out to 4. 10 and that will put me almost exactly back to the orriginal gearing. I have a weekend warrior trailer that I tow and I don't like the mileage that I'm getting with the taller gears. They are way too tall now.

 

[athompson]

Like FF1607, I have the 6 speed, but I have to disagree about the 3. 54s. I find that they are a bit too low for me. I'm always looking for 7th gear. I don't know how anyone could stand the 4. 10s. Maybe when I go for the 44s the gearing will be about right.



I also have to disagree with The Rackman about the drift. The stock Michelins were by far the worst tires I have ever had. My MT/Rs don't drift at all. Unlike him, I'm running 80 at 2K, but I usually run between 1100 and 1600 for most of my driving with no problems or lugging.

 

[Patriot Diesel]

315's...I love 'em

I am running 315/75-16 Pro Comp Xterrains on the 8" factory alloys. I do have the 3. 54 gears with a DTT set up Auto. Yeah it is definately slower off the bottom than with stock 265's but since I have approximately 2. 5 times factory HP I don't mind at all. Cruising at highway speeds (65-80 MPH) is fantastic. RPM's are around 1600-1800. I keep it locked out of OD unless I am above 60 MPH... works great for me.



If I went with taller tires(38's or more with more lift) I would go to a 4. 10 or 4. 56 gear. But with 315's I am perfectly happy with 3. 54's...

 

[Skipjack24]

Hey thanks for the info!!



Patriot Diesel -



Do you tow with your set up and if you do how heavy and do you use OD??



Thanks again for the info. My transmission is currently a BD but I may run up to Canada later this year for DTT.

 

[Patriot Diesel]

towing with 315's

hhhmmm...



I have not towed with the 315's. We did have a 32' 5th wheel, I towed it many times with 305's. No problems whatsoever. Pick a speed and just go with it. I did not run OD while towing under 65MPH. It towed really nice at 70-75 MPH. Just like it wasn't there. I believe that our 5th wheel was approximately 8500 lbs.



jeff

 

[6shotz]

Skipjack,



I'm an auto w/ 315's and 3:54's and I keep the overdrive off till I get to about 65 MPH. 4:10 is in the spring to bring the engine back to what it was when I had tiny skinny tires. EGT will also drop when back to proper gears. Right now if overdrive is on tach reads 1750 @ 70 MPH, about 1450@ 55MPH



Steve

 

[Skipjack24]

Thanks for the info guys!



I've just been trying to figure out if the 315's are worth the lower rpm's when dealing with freeway traffic.



I still wonder about the towing with them in overdrive. My truck has the juice but even on the flats it means towing fast to keep the truck safely above 1600 rpm. And while doing that I have the engine constantly boosting high teens low 20's. Seems like a lot of unnecessary pressure. 3rd gear nets better EGT's, lower boost numbers, higher rpms, and lower fuel economy. If I towed just a bit more the 4:10's (or 3:73's) would get the nod!