quicksr20

Hey guys, I've searched high and low for an answer to this, but every time I find a gear related question for my 2500 with the 6.0 and 35in tires it is the 4 speed tranny. I have the 6 speed(6l90/2008 2500HD I guess) and I have 3.73's right now and a 295/70/17(33.5in). I have the truck lifted around 4 inches right now and I am going to go for a Zone lift 6in w/my keys and Cognito UCA's to get 7 inches this summer and a 35in tire. My question is, what gear is best for this truck(which is heavy and has the wind resistance of a greyhound bus lol). It has the 14 bolt 10.5 FF rear end(g80) and 9.25 ifs up front. I dont hardly EVER tow, mostly just make trips to home depot and maybe once a year take it on vacation. On the last vacation, going up hills on the insterstate at 70mph was a constant downshift and got annoying. I am just deciding on a 4.56 gear or 4.88 to make the tranny stop shifting and converter locking up so much, and make the 35's turn like a stock size tire. What do you guys think? Like I said , all gearing questions were either on street/strip trucks or 4 speed 2500's and no 6 speeds with a lift/bigger tires. btw, I do have a cai/cat back exhaust/and handheld tune. Thanks for the help.

iamkeniff

iTrader: (16)

4:56s since the only gear between 3:73 and 4:56 is 4:10s, an being a lifted/heavy tire the 4:10s may not be enough.

also look into a 37" vs a 35" bc i think the 35" will be too short for a 7" lift.

quicksr20

Do you think a 37x12.50x17 would fit? I would love to cram a 37 on. Would a 4.56 be enough with the 6l90? I have -4.5 bs and -12mm offset on my wheels(Fuel Hostage). I have already trimmed my wheel wells and got about 3 more inches of room all the way around. 37's are heavy!! I saw some that were like 86lbs each!! 4.88 gear here I come lol

fredkj3

iTrader: (1)

http://www.f-body.org/gears/

play with this it will let you know what kinds of RPMs you will be running when the converter is locked in 6th gear...

6 spd gear ratio is 4/2.3/1.5/1.15/.85/.667

1Bear

iTrader: (1)

At least something to make comparison’s by.
Possible stock sizes depending on options:
LT265/70R17E = 31.6”
1575rpm @ 60mph with 3.73's

LT265/70R18E = 32.6”
1527rpm @ 60mph with 3.73's

LT265/60R20E = 32.5”
1532rpm @ 60mph with 3.73’s

LT295/70/17E = 33.3”
1495rpm @ 60mph with 3.73's

35”
1422rpm @ 60mph with 3.73’s

35”
1563rpm @ 60mph with 4.10’s

35”
1739rpm @ 60mph with 4.56’s

35”
1860rpm @ 60mph with 4.88’s

iamkeniff

iTrader: (16)

2000 rpm w 4:10s an a 275/55/20

dlt76028

iTrader: (13)

5.13s with 37s imo. or you could always drop it to 5th gear and the rpms would jump up around 500 more.

play with this calculator some.
http://www.csgnetwork.com/multirpmcalc.html

quicksr20

thanks very much for the replies! I am going to try to lean towards a 37in tire and a 4.88 gear maybe. I think that would be perfect. I also plan on throwing in a True track posi replacing the g80(ive heard some bad things with the 1/2 ton rear ends with them). Its crazy that a set of 37's will cost me more than the gears and true track setup, lol..

J-man67

I would do at least 4.56's with 35's with the 6spd. 37's, def do 4.88's. I have 4.88's, but I have the 4spd. Also your rear should be the 9.5 SF 14-bolt. The G80 in the 14's is A LOT better/stronger then the ones in the 10b. A true-track is still nice, but not totally necessary for the 14 bolts. Good luck with everything.

ig109

No SF in a 2500... Im pretty sure they were all FFs..