diff gear?

[kbenz]

what would you say would be a good gear for a 84 k10, sbc, sm465, np205 with 33" tires? This is my hunting rig but sees the road alot going to and from the club. currently has a 2.56. I currently have to start out in low gear. backing up it's best to put tc in low. only trailer I pull is a 4x8 4 wheeler trailer and that is very seldom. I'm thinking maybe 3.55?
Are the ring and pinion the same front to back?

Thanks

 

[total newb]

Yeah you sould def do 3.55s, maybe 3.92............

 

[arse_sidewards]

3.73 would probably be fine. 3.55 seems a tad high to me seeing as you're on 33s.

Why the fuck do you have 2.56s in there?

 

[NorCalJalopy]

I had a 72 suburban with the same running gear and ran 31’s to 35’s through the years. 3.73 was my happy spot.

 

[total newb]

3.73 would probably be fine. 3.55 seems a tad high to me seeing as you're on 33s.

Why the fuck do you have 2.56s in there?

2.56 because the fucking 80s epa smog bs.

My dads 86 2wd was a 305/700r4/2.56 truck, would 70@ about 1800rpm

 

[total newb]

With gm its 3.42 or 3.73


3.55 dont exist.

 

[arse_sidewards]

2.56 because the fucking 80s epa smog bs.

I know all the OEMs did high gears in the 80s but 2.56 on something that comes stock with an approximately 30" tire is just stupid and beyond the point of diminishing returns on a carb'd vehicle that is gonna richen it up at WOT regardless of vehicle speed so you can't take full advantage of open throttle and low pumping loss at highway speed. But these are the same engineering departments that came up with "limp mode" so I guess my expectations were too high.

Ford never went taller than 2.75 on 2wd and 3.05 on 4wd trucks. Dodge was about the same IIRC.

 

[posford]

You're going to need 1 tons and 5.13s

 

[kbenz]

yeah. it was originally a 700r4 and a np205. I'm turning 2000 rpms at 80mph

edit. it was a np208. np205 now

 

[JR4X]

My brother in law likes 3.73 in his square bodies on 35’s.

 

[kbenz]

Are the ring and pinion the same front to rear?

 

[TrailTamer]

I think so.

and

Don't forget you'll need 2.73 and numberically higher carriers too

 

[kbenz]

I think so.

and

Don't forget you'll need 2.73 and numberically higher carriers too

I thought you could go from a 2. series to a 3. using a spacer?

 

[TrailTamer]

You can, but not recommended.

 

[total newb]

Its

I know all the OEMs did high gears in the 80s but 2.56 on something that comes stock with an approximately 30" tire is just stupid and beyond the point of diminishing returns on a carb'd vehicle that is gonna richen it up at WOT regardless of vehicle speed so you can't take full advantage of open throttle and low pumping loss at highway speed. But these are the same engineering departments that came up with "limp mode" so I guess my expectations were too high.

Ford never went taller than 2.75 on 2wd and 3.05 on 4wd trucks. Dodge was about the same IIRC.

"Epa estimated mpg"

Its the epa, logic doesnt apply.

 

[Oddball]

I vote 373 or even 410 if possible

 

[subybaja]

Obigatory post.

Gear Ratio Calculator

 

[M92PV4U]

I would go 4:11 our 47 EDIT 74 NOT 47 1 ton was 454 465 14b 4:11 225 75 16. It drove down the highway fine.

 

[JR4X]

Obigatory post.

Gear Ratio Calculator

Something tells me that isn’t going to mean anything to the op. I love that thing. Have it saved to my favorites and use it all the time

 

[Oddball]

I prefer this one, it's simple

Spicer Transmission Ratio RPM Calculator

Use the Spicer Transmission Ratio RPM Calculator to determine your engine’s RPM based on the transmission gear ratio, tire height, MPH, and ring and pinion gear ratio.

spicerparts.com

 

[Oddball]

2500 rpm at 60 mph with 33s in 4th and 410 gears

 

[Provience]

2500 rpm at 60 mph with 33s in 4th and 410 gears

in that case, 4.56 or 4.88

 

[Weasel]

agree ^ 4.56 or better

run 4.56 in my XJ with 33's and it was happy.

 

[Oddball]

in that case, 4.56 or 4.88

Circling back to tons and 513s here

 

[total newb]

Circling back to tons and 513s here

No shit. Who the fuck would spend $ on 10s.

 

[AKnate]

I ran 4.56 on 235/85r16s and sm465 on a C30. Worked well for hauling though was a ~60mph truck.

 

[kbenz]

Might have found a donor truck. 78 k10 bonanza. from what I've read it should be a 12 bolt with 4.10's. $400.
work is a bit slow. so I'm on a bit of a budget

 

[subybaja]

Might have found a donor truck. 78 k10 bonanza. from what I've read it should be a 12 bolt with 4.10's. $400.
work is a bit slow. so I'm on a bit of a budget

If the 410s are what you're after, make sure it's got em. Cover tag or ring gear stamp.

 

[YotaAtieToo]

Might have found a donor truck. 78 k10 bonanza. from what I've read it should be a 12 bolt with 4.10's. $400.
work is a bit slow. so I'm on a bit of a budget

Just grab those

I had a cucv. 6.2/th400/4.56s and it was nice for everything but pure highway.

 

[total newb]

If the 410s are what you're after, make sure it's got em. Cover tag or ring gear stamp.

No tags on "gm" diffs.

A marker, a couple tire rotations, and youll know for sure.