So what you're stating...towing (5k) w/my current setup @ 1700 rpms 70mph is to much strain on the tranny? Shifting in/out of OD when starting out @ lights definately helps. Temps run about 180* on a 95* day.

 

If your directing your comments toward me, I was addressing the posters comments shown in the quote. I assume your happy with your set up.

Dave

 

3.54 at 80 mph, with 315's is 1800 rpm!
Great if empty but towing ...............?

You posted in the 2nd gen forum but you have an 05?? Is 3.54 available on the AAM rear end.
I'd go 3.72 if towing a lot... especially with 315's.

RJ

 

Glad I read this thread . I need new tires and thought I wanted 315/75/16s up from my 285s . But Had decided to stay with 285/75/16s with my 3:55 gears for towing my 24ft 5th wheel . Bigger tires I know I would be grunting it towing big time. Or haveing to drive OD off and slower speed just to keep the RPMs up

 

diffinately wouldnt do an auto with 315s unless its has 4:10s. thats the nice thing about a manual tranny there are plenty of gears to pick from.

 

Yea I am kinda missing my 6 speed Duramax right about now. Auto with 315's and 3.55's have kinda been a head ache.

I was looking through a summit magazine and saw there was a set of 3.90 gears for a dana housing, will this work in our applications or are 4.10 gears my only alternative?

 

I have 3.55 and soon be putting on 37" so I will post whats going on what and when with the 6 speed.

 

I run 33-12.5-16.5 with 355 gears and a 6spd trans and at 70 mph I am running 1942 RPM

 

How do you guys like the 3.55's. My truck seems like it does not have any ***** at all! I know there is a huge difference between automatic and manual but any information?

 

with current 35's I have no problems with the 6 speed. great on the freeway and screaming around town at 2k-2300 rpm. will see when I install the 37's next week. and I do have 3.55

 

With 35s and larger 410 would be great to reduce stress on the drivetrain and incress rpms to where they are suposed to be. I have 410s and am looking to switch to 3.54 if you are near California. 3.73 is as low as you can go with 3.54 cariers but I dont see the point since its not much of a difference and there are plenty of us 410 guys that are looking to trade.

 

I use 315's and tow a 32 foot fifth wheel. Towing it at or close to posted limits over mountains from sea level to almost 7,000 feet with no problems. Had to drop down to 5th for a couple of the steeper grades. According to the overhead I am averaging 11.4 mpg for my last trip of over 2000 miles.
At 1900 rpm I am indicating 70 mph. The speedometer was recalibrated by the dealer when I switched to 315's.

 

I've got 315/70R17s with 3.55 gears and it cruises nicely on the freeway. Unfortunately, it wants to cruise at 85+mph to get into the sweet spot. I'm at 1500rpm at 60mph and 1900 at 80mph. Still spins the tires pretty easily once the turbo spools on anything above 3x3. I think this size tire would work well with 3.73s or 4.10s....

 

Did the 37's fit on your 02? Did not think they would.

I did some math and was surprised....
From 32" (265's) to 35" (315's), with 4.10 = 3.75
From 32" to 35" with 3.73 = 3.41

With my 315's and my 3.54 gears, I'm at 3.27 rear end ratio. Works ok and gotten use to it (not towing heavy) but it sounds like a pretty tall gear ratio.

RJ

 

With a Skyjacker 4.5" lift and 10" wheels with +10mm offset (and no off-road articulation to speak of) the 37s work fine. I have never rubbed a tire on the body or suspension.
The 3.54 gears and 37s are great for me. Towing in 5th at 60mph is 2000rpm. 6th gear empty is 1750-ish around 70mph. The only downfall is hitch height (and the price of tires!). IIRC my effective ratio comes out to 3.00, but 1st gear is actually useable!