Different Ring and Pinion Ratios

[Rinkrat456]

I've asked around on other forums I belong to (MyS10 and S10forum) and no one could give me a straight answer. From my past answers, let me explain the situation before everyone wants to begin tar and feathering me.

-The project is a 2001 regular cab Sonoma 4wd, with a BW4472 t-case from a 95 Bravada.
-Lowered 3/3 with Belltech keys and Belltech drop leafs, but I like what I see with the coilover setup so that might be my next project after this rear end swap.
-Aluminum 5.7L LS1 almost finished, mated to a Raptor 3 4L60E, with 125hp Edelbrock nitrous shots at the track
-Front differential has 3.42's, and I think that is the perfect ratio for having fun on the streets and also maintaining daily driver manners.

The GM 7.625" isn't strong enough stock to handle 450 fly wheel horsepower and the type of abuse it will see. Granted only 65% of that is actually going to the rear because of the t-case and 65/35 power split but I'd rather not tempt fate. The GM 8.5" out of 2wd 4.3L 5-speeds isn't wide enough, and I'm not a fan of 2" spacers, at least not on a performance oriented vehicle. The GM 8.5" out of a ZR2 is too wide, and I'd rather not have to buy new rims just because of the axle being 2" wider on each side. So those are the only GM axles I'd consider from an S10, and the Ford 9" is weighing in on the heavy side after all my weight reduction efforts, and frankly is too expensive to get from Currie built to my specs, same with an 8.875" GM 12 bolt.

Here's what I have instead as a proposal: The Ford 8.8. I already have the axle which used to be in my 96 Sonoma before it got lifted 15" on 35's, so it's just sitting around collecting dust in my garage. It has an Eaton limited slip posi, currently 3.73's (no big deal for me to change ring and pinion sets), 11" disc brakes and is already drilled for the 5x4.75" S10 bolt pattern. The rear is 3/4" of an inch wider than my stock 4wd rear end, measuring in at 59.75" from WMS to WMS.

The Ford 8.8 unfortunately doesn't come in 3.42's, the closest ratio being 3.55. If my math is correct, I believe I can keep the final drive line ratio the same as the front if I use the correct tire size. 3.42's and 26.1" tall tires up front (255/45R17) and 3.55's and 27.1" tall tire in the rear (285/40R18). I already have the rims (17x8.5 and 18x9), and I work at Discount Tire so no problem getting the tires. Having a rear tire larger in the back would be nice, as I like a good raked stance to my trucks.

My question is, does anyone have any experience in running different ring and pinion ratios in an AWD vehicle?

 

[SY2455]

Re: Different Ring and Pinion Ratios

Dumb ? follows. Why not look for a 3.73 ratio front diff from a 2.5L or a 2.8L 4X4 truck?

Now to your ? If you look over this you will find your answers.

Front Suspension: Pushrod activated A-arm shortened 2" on each side billet aluminum spindles by Summit, HAL Star AL adjustable shocks, HAL springs, GMC Syclone differential with custom half-shafts by Summit, 3.43 gears and limited slip

Rear Suspension: Four-link HAL coil-over shocks, custom antisway bar, Corvette ZR-1 center section with 3.73 gears and limited slip differential

Wheels and Tires: One-off Billet Specialties wheels (18 x 8 front, 20 x 10 rear), BFGoodrich GForce tires (235/40ZR-18 front, 275/35-20 rear)

OR look at this.

http://www.syty.net/forums/showthread.php?t=33615&highlight=Quadraduece

 

[supersports10]

Re: Different Ring and Pinion Ratios

95 and newer 4.3 ho with a 5 speed 4x4 came with a gm 8.5 non zr2 with 3.42, and disc brakes

2wd also came with this rearend. (shorter of course.)

 

[Rinkrat456]

Re: Different Ring and Pinion Ratios

Dumb ? follows. Why not look for a 3.73 ratio front diff from a 2.5L or a 2.8L 4X4 truck?

Now to your ? If you look over this you will find your answers.

OR look at this.

http://www.syty.net/forums/showthread.php?t=33615&highlight=Quadraduece

Good to know. His ratios worked out just fine and that's the math I was looking for. It's simple 4th grade math really....cross multiplication. I just wanted a reaffirmation that I was right.

The reason I'd like to stick to 3.42/3.55 is because of my smaller tire size and top speed goal I have. Not only that, but this Sonoma will become my daily driver (96 Sonoma lifted up that tall is getting 12mpg) and most my driving is all highway. With 3.73's front and rear (which would make my job 10x easier) will put highway RPM's above what I'd like to cruise at with an LS1.

 

[Rinkrat456]

Re: Different Ring and Pinion Ratios

95 and newer 4.3 ho with a 5 speed 4x4 came with a gm 8.5 non zr2 with 3.42, and disc brakes

2wd also came with this rearend. (shorter of course.)

I've addressed the 2wd 8.5" already, and I don't think the 4x4 info is correct. All my manuals state that only ZR2 S10's and a select few (meaning not all) 2wd 4.3L 5-speeds have the 8.5" rear. Either way, one is too wide and the other is too short.

 

[SY2455]

Re: Different Ring and Pinion Ratios

The reason I'd like to stick to 3.42/3.55 is because of my smaller tire size and top speed goal I have. Not only that, but this Sonoma will become my daily driver (96 Sonoma lifted up that tall is getting 12mpg) and most my driving is all highway. With 3.73's front and rear (which would make my job 10x easier) will put highway RPM's above what I'd like to cruise at with an LS1.

I must have look at your posting wrong, I thought you were wanting to keep your 3.73 gears and just retire for the difference in ratio. Anyway the posting above will still answer it.

 

[supersports10]

Re: Different Ring and Pinion Ratios

I've addressed the 2wd 8.5" already, and I don't think the 4x4 info is correct. All my manuals state that only ZR2 S10's and a select few (meaning not all) 2wd 4.3L 5-speeds have the 8.5" rear. Either way, one is too wide and the other is too short.

nope.. my x gf's friend, had a 98 reg cab 4x4 non zr2 5 sp, and it had the 8.5 factory.

it had 4000 miles on it when i looked at it.

i told her right there, if she ever sold the truck, i wanted it....bad!!

 

[Rinkrat456]

Re: Different Ring and Pinion Ratios

nope.. my x gf's friend, had a 98 reg cab 4x4 non zr2 5 sp, and it had the 8.5 factory.

it had 4000 miles on it when i looked at it.

i told her right there, if she ever sold the truck, i wanted it....bad!!

Ya that would make our lives a lot easier...well yours if you have a Sy/Ty, mine if I wanted 3.42's all around. I kind of like having offset drive line ratios though, I love old school muscle cars with the big n' littles, and having a slightly larger (by less than 1") tire in the rear I think it'll look and perform perfectly. Since I already have the 8.8, the only cost to me is the 3.55 ring and pinion set and a driveshaft rebalance.

I've been under countless S10's in my line of work, and it's odd that I've never seen a 4x4 non ZR2 with an 8.5". They're hard to distinguish to the untrained eye, but every truck I've seen is a 7.625", even the BlaZeR2's. It's also odd that my 3 manuals say nothing about this.

 

[gkrcr882]

Re: Different Ring and Pinion Ratios

Probably something you already knew, but...you have to have the same front/rear ratios along with the same (if not incredibly close) outer tire diameter front/rear with the 4472 case, otherwise it'll burn up the VC:2cents:

 

[Rinkrat456]

Re: Different Ring and Pinion Ratios

Probably something you already knew, but...you have to have the same front/rear ratios along with the same (if not incredibly close) outer tire diameter front/rear with the 4472 case, otherwise it'll burn up the VC:2cents:

Actually this is mis-information, but true to a degree. The actual truth is that with the 4472 case (and most other AWD platforms as well) the FINAL DRIVE LINE RATIO must be the same, front and rear. By combining the right ring and pinion ratios with corresponding tire sizes, the final drive line ratios can be equal, meaning one is capable of running a taller and possibly wider tire in the rear than the front.

An example would be my solution to the rear end problem. 3.42's and 26.1" tires in the front, 3.55's and 27" tires in the rear. These two drive line ratios are within 1% of eachother, and actually letting about 3-4psi of air out of the front tires would make the front and rear drive line ratios exactly the same.

Edit: In fact, this just came to me now that I think of it, tire sizes are determined by mounting the tire on the rim, airing up to 32psi (all tire manufactures do this) and then reading the final tire height with 100% new tread. My front tires are 26.1" tall, and I need them to be 26.04 to make my final drive line ratios EXACTLY the same. When I mount these rims and tires on my truck, the front will naturally compress the tires more because of the heavier weight of the front. So, in common speak, the tires and rims and ring and pinion sets I chose will work out perfectly.

Another example is the setup in post 2. 3.42 up front and 3.73 in the rear in his or her AWD vehicle, with 25.40" tires up front and 27.58" rear. IMO, that's a little extreme, but it just goes to show how an AWD vehicle does not need the same ring and pinion ratios in both front and rear differentials, along with the exact same tire sizes.

What's important is the final drive line ratio.

I hope that helps clear things up.

 

[turbodig]

Re: Different Ring and Pinion Ratios

Working the math you posted....


3.42/29" (Stock rear, 29" tire) = 3.08/x

... works out to 26.1, if my math is correct.

I would think this would be a a good thing for the *really* fast guys, allowing them to run a big 29" tire, while keeping the front size the same. (By putting 3.08 gears up front)


Just thinking out loud...

 

[Rinkrat456]

Re: Different Ring and Pinion Ratios

Working the math you posted....


3.42/29" (Stock rear, 29" tire) = 3.08/x

... works out to 26.1, if my math is correct.

I would think this would be a a good thing for the *really* fast guys, allowing them to run a big 29" tire, while keeping the front size the same. (By putting 3.08 gears up front)


Just thinking out loud...

Your math is correct. Good thing 26.1" tall tires are very common.

You're in Sabin, MN huh? East Twin Cities, MN here.

 

[Tooky]

Re: Different Ring and Pinion Ratios

I wonder if anyone has ever burned up the VC in the 4472 due to mismatched tires, even grossly mismatched tires. ???

 

[Rinkrat456]

Re: Different Ring and Pinion Ratios

One thing that's had me wondering for awhile, if the t-case can support less than a 1% difference in final drive line ratio, where does that slack go? Say the rear tires are new on a stock Sy/Ty, fronts are bald.

 

['JustDreamin']

Re: Different Ring and Pinion Ratios

One thing that's had me wondering for awhile, if the t-case can support less than a 1% difference in final drive line ratio, where does that slack go? Say the rear tires are new on a stock Sy/Ty, fronts are bald.

The VC would end up absorbing the difference. It's what ends up absorbing all the little differences.

The reason that you're looking for as close a match as possible is to keep from putting a bunch of heat in the VC by running slightly different speeds and getting it to lock up (or just plain bake) when it doesn't need to lock up.

I didn't look at your math closely, but the theory about running different tires & ratios is sound. I think its a good solution, since you already own the 8.8 Ford and the 8.5" 10 bolt is difficult to find (seems like every yard thinks they have one but they all turn out to be 7.5" POS's).

You will need to figure out what to do for spare tires. Flatbed only, 2 spares, runflats....You've got options, just need to decide what you're going to do before it happens.

Hope the 4L60E holds up. I know that'll be the weak link in your driveline, especially with 450+ hp and a 125shot. The rest of the parts you're either addressing (rear axle) or you aren't likely to break (BW4472).

Who's oilpan did you use (or did you build one?)

Good Luck

'JustDreamin'

 

[Rinkrat456]

Re: Different Ring and Pinion Ratios

Ahh, I see what you mean about excess heat in the VC absorbing the difference. My front:rear ratio is off by 0.028 percent, I figure, after weight is put on the tires. Speaking of tires, I just put in the order for them today at work. 255/45R17 front, 285/40R18 rear, Nitto NT-555's. Thankfully this isn't my daily driver, otherwise I wouldn't be able to get to work lately. I didn't even bother with spares or extra tires/rims for winter use. I drive the supercharged HHR to work every day (27mpg woohoo!) , and my lifted Sonoma during the fall/winter or whenever hunting (12-14mpg :rant: ). This AWD project is just a toy in my spare time. I have certificates for free replacement through work, so if I catch a nail in the sidewall or a tire pops, I get a new one free.

The oil pan used is a variation of the LS2 shallow pan, meant for the 55-57 Chevy conversions made by S&P. I still had to notch around the differential, but made up the oil capacity by making the pan deeper, still with about ~5qts capacity, in addition to an oil cooler. The sump hangs just a little lower than the front differential, and I don't think the end stance will sit much lower than a stock Syclone...maybe an inch. I'm really impressed by what I see with the coilover setup, so that might be purchase number next. For how cheap just the coilover kit is, I think 70lbs lost and a stiffer suspension is well worth $500 or so.

What pan did you use for your 6.0l or haven't you gotten to that point yet?

I too hope the 4L60E holds up, but I'd look elsewhere to a 6L80E first if this one breaks before going to the 4L80E. That's another post for another thread some day later on if I break the 4L60E. Right now, it should be fine, brand new. For good measure, a tranny cooler is going under the bed, 7-1/2x10" with a 7" electric fan switched on whenever the t-stat reaches 190 degrees.

Tomorrow is my first day off in the past 12, along with another 8 coming up, so you bet I'm working on the truck tomorrow. In the morning I'm going junkyard hopping looking for an Xtreme/ZQ8 12.7:1 steering box, and will hopefully come across the full truck so the sway bars front and rear are available for the taking. If not, S10warehouse has them on eBay.

Anyways, thanks for the insight about the VC/driveline differences.

 

[Black Knight]

Re: Different Ring and Pinion Ratios

You don't think those tire sizes being an inch in diameter difference from each other will cause you any problems? :dunno:

P255/45R17 revs per mile 775
P285/40R18 revs per mile 748

 

[Rinkrat456]

Re: Different Ring and Pinion Ratios

You don't think those tire sizes being an inch in diameter difference from each other will cause you any problems? :dunno:

P255/45R17 revs per mile 775
P285/40R18 revs per mile 748

Not one bit actually.

Try reading the whole post, or for starters, the title. :rotf:

 

['JustDreamin']

Re: Different Ring and Pinion Ratios

What pan did you use for your 6.0l or haven't you gotten to that point yet?

Built my own pan from steel sheet and barstock. Decided it was easier than trying to hack and chop on an aluminum pan, especially since I can weld steel and not aluminum.

Truck runs, and runs pretty well. Still have a few little bugs to work out, I'll get to them sooner or later....

I've been contemplating the coilover stuff too....But am going to wait on somebody else with a 2nd Gen trying it out, and getting my garage addition built (a much bigger priority).

'JustDreamin'

 

[Rinkrat456]

Re: Different Ring and Pinion Ratios

I've been contemplating the coilover stuff too....But am going to wait on somebody else with a 2nd Gen trying it out, and getting my garage addition built (a much bigger priority).

I have a 93 4x4 S10 frame a friend and I have been working on mounting a '50 Chevy 3600 body and bed to in our attempts to restore the truck with the addition of a mean stance. I've been looking at the differences in the front suspension and it seems like the 2nd gens have it made. The upper A-arm looks to require no grinding, or at least way less, and the lower shock tab looks more reinforced compared to 1st gens, easing my initial worries about the lower tab being able to support the weight of the truck in spirited driving conditions.

School is coming up soon in just another 2 weeks, so unfortunately I think the 8.8 swap is my last project of the summer. I'm fairly certain now that coilovers are the answer, so if/when I get them I'll be sure to take pics and document the installation for you and others inquiring.