S-10/Sonoma rearend gearing?

[ThomCat316]

I am starting to improve my 1996 Sonoma, and have to dive into suspension issues first, therefore this question.

Which rearend gearing gives best overall functionality? The truck is stock with 4.11 gears, which usually make 1st gear an effete affectation, but there are times (like the past week) when I have to hitch up the 1,000 lb. teardrop trailer and drive over hill and dale to get to various trade shows. With this load 1st becomes a bit more useful, and 5th starts to seem a bit optional - at least up any noticeable incline.

I had sourced and was ready to purchase a nice 3.08 axle off the same vehicle, but now I am wondering if I really want to get that steep with the 4 cyl. engine.

Current long-haul numbers:
22 MPG with loaded trailer
24 MPG with either light trailer or two sea kayaks on the roof
29 MPG naked

Any real-life experiences that can guide me toward a particular ratio?

Thanks,
Whitney

[Slow_s10]

If it was not for the fact that you regularly tow a trailer I would say go for it with the 3.08s but since you do usually tow I would reccomend splitting the difference and finding a 3.42 rear end. It is still much taller than the 4.11 rear end but it leaves enough on the table to manage towing with the 4cyl.

I'm assuming your truck has the NV1500 transmission, in which case the transmission ratios are:

First: 3.96 Second: 2.37 Third: 1.49 Fourth: 1.00 Fifth: 0.83

If you multiply that by your current rear end ratio and the proposed 3.08 you get final drive ratios of:

4.11
First: 16.27 Second: 9.74 Third: 6.12 Fourth: 4.11 Fifth: 3.41

3.08
First: 12.19 Second: 7.30 Third: 4.58 Fourth: 3.08 Fifth: 2.56

As you can see the ratios become a lot higher. If you look at the ratios above with the 3.08 your first gear would be alot closer to your curent 2nd gear ratio than your current first gear ratio. Also by the time you get into 4th gear the ratio is now even higer than your old 5th gear.

Here is how the final drive ratios would look with the 3.42:
First: 13.54 Second: 8.11 Third: 5.01 Fourth: 3.42 Fifth: 2.84

As you can see the ratios are still much taller but first gear will still be a little more usable and by the time you get to 5th the difference between the 3.08s and 3.42s becomes almost negligable. In this situation your new fourth gear would have almost the exact same ratio that your current 5th gear has.

Oh and assuming you have stock sized tires at 55mph your engine RPMs in 5th would be:
4.11: 2350
3.43: 1950
3.08: 1750

But that's just my 2 cents. If nothing else I hope it can at least help make your decision a little easier.

[Cobb]

22,24,29, looks like aero maybe more benefical than gear.

[JRMichler]

You have a good feel for the gear ratio tradeoffs. I suggest working on aero and rolling resistance first. Aero would include grille block, wheel covers, belly pan, possibly an aero topper. Rolling resistance is tire pressure, front end alignment, and LRR tires. And a kill switch.

Don't forget aero for the trailer. Teardrop trailers look terrific from the side, but those square corners in the front can cause problems.

When you have done all that, then reevaluate gear ratios.

MTA: Plus what Cobb said.

[ThomCat316]

Originally Posted by JRMichler

I suggest working on aero and rolling resistance first.....
When you have done all that, then reevaluate gear ratios.

I agree....but.

I have an immediate need to take the front end entirely apart to replace various bits which don't work anymore, and while it's apart I plan to change a few from stock to lowered. If I'm lowering the front 3", I imagine I should drop the rear about 4", which requires disconnecting the axle. While it's unhooked, maybe I should spend ca. $150 more and swap it? <---Train o' Thought, Illustrated!

I read on here that these trucks benefit from being lowered and dammed/skirted almost as much as from being smoothed beneath, and a lower roofline allows for kayaks to be loaded more easily, too. On top, I'm planning sport mirrors and am holding my breath waiting for A8KSH4's project (which, apparently, I'm ALMOST able to link to - one more post) to get to the A-B-A testing and numbers phase before I start building molds myself.

I am going to start working on engine mechanicals next month and getting a Scangauge, as well as swapping over from engine fan to electrical fans. I don't see myself going full-blown fanatical with eco/hyper driving and mods, but the stuff that's simple for me and nets a decent cumulative gain will get done. I don't think I'll be springing for LRR tires for this one - it's almost twice the cost - but I'll make sure I keep the Kumho's topped up regularly.

I like the killswitch idea, but it's first getting applied to the A/C compressor! :-) GM, in their infinite wisdom, does not think I would like a cabin-air-recirculate setting without the compressor running. Gotta fix this.

Thanks to Cobb and JR for setting my priorities in the real order, despite whatever I'll end up doing with them - and also for the photos of JR's Canyon, which helped me reassess how I'm going to build my aerolid.

Thanks to Kevin for walking through the math with me in a more methodical way than I already had - I think you're right about the 3.42 gearing - if only it were simpler to swap rearend gears! I only need the 3.42 about five or six weeks a year, the remaining 45+ are spent driving around Flatland with no real resistance.

I appreciate the help!