Best gear ratio for 8 inch lift and 40s?

[AuroraGirl]

I’ve already fixed the crack and reinforced at the steering box so that won’t be an issue. I’m going to go with cross over steering and I have dual stabilizers on it already. I’ll look into spicer but I’m pretty sure I’m going to go with 4.56s, also what would be the best way to stop driveshaft vibration if it happens, lengthen the driveshaft? or could I run a spacer and tcase drop bracket kit? thankyou all for being so helpful to this young guy who’s just getting into these older trucks!

angles and balance. (and good u joints) and correct phasing so your drivetrain cant have too extreme an angle , so strong mounts that place it in the right angle should resist twist and bind up if that were to happen. i hope

 

[78k10bro]

Also wondering what steering box to use for cross over steering if anyone has some recommendations? Not going to go with hydro assist.

 

[nvrenuf]

are you talking about the new process overdrive trans? @Keith Seymore has one of those I think,starts with an A or something I think

Yeah, I believe it's an "A833" but I'm not sure. Since there was almost zero chance of the OP having one I focused on the SM465 granny 4 spd.

@78k10bro check you're driveshaft vs pinion angle for the vibration, you might be able to shim the rear springs to fix it but usually it takes a double cardan type joint assembly on the driveshaft at the tcase to truly fix it.

 

[bucket]

Just use the 2wd version of steering box for the crossover steering. It will have the correct sector shaft for use with a crossover style pitman arm.

4.56 gearing will work, but with 40's, I'd go 4.88 or 5.13 gears. Intersrate rpm will not be excessive, but the engine will be more in it's powerband to combat all the wind and rolling resistance.

 

[Rumbledawg]

i'll throw my $0.02 in as well, as i drive a lifted chebby with both 38's and 42's.
my combo is a little different than yours-454/T400/205. i have factory 4:56's and i find them about perfect whichever tires i'm running. truck will snap off the line like greased pig snot (surprised a few imports, mustangs, camaro's and a bimmer once...) freeway is best at 60mph or lower. with a 1:1 trans, my tach hangs around the 3 grand mark at 60mph-glug, glug, glug....
instead of driveshaft spacers, use a cv and a high angle yoke. belive it or not, i'm using the stock fr driveshaft on my 8" lifted crew. ground out the cv stops and added a longer, high angle yoke, never had any issues. my rear shaft is also stock, but it's a 2 piece'r with a dropped steady bearing, i did lose about 1/2" of slip on the shaft, but i've never managed to pull the other 4"s out-ever.
you will haft to shim your axles to keep your drivelines reasonable, or use tapered lift blocks. a small (1") t-case drop can also help your angles.
you will definitley want to run crossover. i once had a dropped pitman, "s" draglink and a steering block, while not bad on the street, they are lacking off road. get your axle dropped, like in a hole, and turn your steering wheel, and the tires will still be pointing strait- can make for a pucker moment. and crossover is completely fine on the street, been running mine for about 7 yrs with zero probs, and it will steer with one finger. i would strongly recommend a GOOD ps box, screw the remans- their junk especially with big rubber. i installed a Redhead box in mine, couple bucks more than a reman, but well worth the money. you really want to scrimp on your steering?
this is the box i'm using

2856 (3 Turns): 1980-1991 Chevrolet or GMC Pickup Trucks, K5 Blazer's, Suburban's or Jimmy's Steering Gear

Part Number: 2856 (3 Turns). Part Number Fits: 1980-1991 GM Pickup Trucks, Blazers, Suburbans or Jimmys. Please Note: This steering gear has a threaded output shaft, which indirectly turns the tires, a nut and washer is used to connect it to the pitman arm. (Please see the second photo on...

redheadsteeringgears.com

 

[78k10bro]

I found a 14 bolt rear and Dana 44 both with 4.56s and it comes with cross over steering. I will look into that steering box and also the drive shaft stuff, thankyou.

 

[AuroraGirl]

I found a 14 bolt rear and Dana 44 both with 4.56s and it comes with cross over steering. I will look into that steering box and also the drive shaft stuff, thankyou.

be careful if youre using a 78-80 ish d44. they.. well.. they dont play nice by the rules when it comes to replacement shafts and seals and stuff.

 

[Keith Seymore]

are you talking about the new process overdrive trans? @Keith Seymore has one of those I think,starts with an A or something I think

If the original poster has an SM465 (with the granny gear) then there is a 110% chance that is is non overdrive.

The overdrive manual trans was a New Process A833, RPO MY6, which was a MOPAR trans with third gear set 1:1 and fourth gear as overdrive.

K

 

[78k10bro]

What yoke would you recommend getting? Also the cvs?

 

[Grit dog]

are you talking about the new process overdrive trans? @Keith Seymore has one of those I think,starts with an A or something I think

A833.
Neat swap or find imo.
Way better off with a 465 for the OPs purposes

 

[Juggernaut]

I ran my truck for several years with 39.5 Super Swampers, 4.10 gears and a 4 speed SM465. The 4.10s work ok, but I always wanted to go higher. I suggest 4.56 or 4.88. The biggest problem I had 4 wheeling was the Dana 44's long axle shaft on the drivers side. I broke that shaft several times, usually broke the knuckle at the u-joint, but I also twisted one off at the splines. Spend the money on a good set of aftermarket axle shafts. I also broke to many drive shaft u-joints to count, that is until I figured out the secret is to use NON greaseable joints! The key is to keep it spotlessly clean when you assemble it, and use a vise to press in the caps, don't beat them in with a hammer

 

[Snoots]

Spicer Driveline Operating Angle Calculator

Measure the angles of each component in your drivetrain, then use the Spicer Driveline Operating Angle Calculator to find the operating angle of each u-joint in your drivetrain.

spicerparts.com

 

[Juggernaut]

https://spicerparts.com/calculators/driveline-operating-angle-calculator[/URL

That's a very good point. At 8" of suspension lift, driveline angles become a real problem. I was always told not less than 1 degree, but not more than 3 degrees. I had a cheap magnetic angle finder I would stick to the bottom of the u-joint cap at the yoke. Then subtract the one number from the other, but this calculator is definitely the better way. That said though, I never broke a u-joint at the cross shaft. Absolutely every joint that I broke had one cap still bolted to the yoke, the other cap gone, and the race on the cross shaft nearly worn in half. I was told that's from contamination. When you over grease a joint and the grease blows out the side, that gives a wide opening for dirt and mud to get in and ruin the bearing

 

[Rumbledawg]

I ran my truck for several years with 39.5 Super Swampers, 4.10 gears and a 4 speed SM465. The 4.10s work ok, but I always wanted to go higher. I suggest 4.56 or 4.88. The biggest problem I had 4 wheeling was the Dana 44's long axle shaft on the drivers side. I broke that shaft several times, usually broke the knuckle at the u-joint, but I also twisted one off at the splines. Spend the money on a good set of aftermarket axle shafts. I also broke to many drive shaft u-joints to count, that is until I figured out the secret is to use NON greaseable joints! The key is to keep it spotlessly clean when you assemble it, and use a vise to press in the caps, don't beat them in with a hammer

all the more better to step up to a D60. they will shrug off a 42" swamp like a 33 incher, bigger brakes, bigger axles, bigger everything.
bigger tires = bigger stress

What yoke would you recommend getting? Also the cvs?

measure your shaft and spline count. my truck is a 1 ton so yours will be diff.
i run a spicer 1350 high angle cv-will flex to approx 35 degrees and run all day at 20 degrees
front slip yoke is approx 10" with about 7" of useable travel
i got mine here

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[Craig Nedrow]

If you go to different gears, Randy's ring and pinion, (Randy's worldwide,) has everything. Yukon brand.