BlackThundah

I had 285s because it was lifted, but 265s would be a nice compromise. I had some before I got my 285s and they were great. I had more power with them yet had a nice size tire for a 2wd. they just didn't fill out my wheel wells enough, so I went up to 285s.

Spannerhead

I've got a 4.6 with a 3.08 and 265/75-16s; no complaints. 22.5 calculated mpg on a recent 400-mile trip.

I drive like a grandma though.

greenheadkiller98

I wasn't really worried about the mpg I was more annoyed by the lack of towing power

Spannerhead

I towed my 240Z from central NC over the Appalachians here to Chattanooga. It's not the heaviest car in the world (~2,300 lbs) but it was on a UHaul car carrier, not a dolly. The bed was completely full of stuff from our old storage unit too. The trans had to kick down a couple of gears a few times but overall it did just fine. You have the 4.2 though, so I dunno. YMMV.

FYI the 22.5 mpg was on the way there, with the bed empty except for Christmas presents and no trailer. The mileage on the way back was obviously considerably worse, but that was the price of admission, so to speak.

greenheadkiller98

I pulled a 7,3 super duty 75 miles interstate at 70 mph and only downshifted for one overpass. That was with 4.10 and 285/75/16 though. It didn't pull for crap with the 3.55 for my uses

I don't have the 4.2 I had a 4.6...
I have a 5.4 now tho ha

justinh11

I have a 97 4.2 5 speed 4x4 3 inch lift on 305/70/16 on 16x10s and actually didn't notice that much power loss and I had 35s on it b4 for 3 years then stepped down a size since I couldn't afford 35s anymore and it hasn't affected the trans or engine

I work on a farm so I've pulled lots of hay trailers and a 18 ft flatbed trailer w/ small jd tractor

bchauler

As was mentioned, h9 is 3.55 limited slip, so if that is the case, you may not mind too much. In the vin says 3.08, you may have to crawl under the truck and look at the rear diff cover. There should be a metal tag that has a series of numbers stamped on it. That is probably the best way (short of opening the diff to count splines) to tell which ratio you have.

My experience was just that: my experience. You may find that the tire change has no effect. My 320 km trans gave up the ghost not long after I swiched tire sizes. Related? Not sure. After replacing the trans with a used trans with 160 km, I noticed I was getting lockup shudder on the highway, and reading on the net suggested that the bigger tires might be keeping the trans outside of its optimal shift range. So I replaced my 3.31 diff with a 3.55 diff (with the bigger tires, 3.55 put my actual ratio closer to the original 3.31). I then drove over 1000 kms on winter trips through the mountains. The truck seemed to run better and the shudder was no longer present.

Anyway, good luck.

greenheadkiller98

Another way to do it is jack up the rear, and spin the rear wheels an count how many times the driveshaft spins in respect to 1 rotation of the tire

Beaterdan

WATCH THIS VIDEO it will show how to count your ratio.

rileycheekf150

i have 285/70/17 on my 4.2 v6 never had any mechanical problems definatley lost power and mileage but got the power back with gibson headers