90 chevy dually rear gear

I have a 1990 chevy dually crew cab that I drive every day. I need to use the freeway but it feels like I'm killing it doing 65mph. My question is can I change the rear end gear for more freeway use?. I don't tow and bought the truck to lower it. On the freeway it sounds like its reving to high? The trucks got 90k original miles and gets a solid 10 mpg. Thanks for any advise on this.

90 crew, still squarebody then right? Also being 90 is last year for TH400 so no overdrive...your rear gears are probably 4.10's, maybe lower. Glovebox sticker still legible?

With that 1:1 final gear in your trans, you probably want 3.73's, but I don't know if gears that high are available for the 14 bolt full floater. Might be, just I've never seen 'em. Your tire size is going to be a factor too. Shorter tire you go with cancels out some of the benefit of a higher rear gear as you'll still be turning faster to reach a particular MPH.

Richard

Actually they do make a 3.73 for the full floater 14 bolt. They came stock in 3/4 ton single wheel trucks. I had them stock in my truck until going lower. And I second the tire size. Maybe run some bigger tires if you can?? and that will act like you changed to a higher gear.

Shitbox FF14s came with 3:42s also.

Wow; I can't imagine how horribly bad 3.42's would be in a shitbox 1 ton, esp a dually. 3.42's suck in a half ton Suburban. Bog off the line and highway cruise speed just under the torque curve, lamest setup ever. Well, about as lame as 3.08's in a shitbox half ton truck.

Richard

They are nice when you have a diesel though, I don't like running my motor up to 2.5-3K to roll at 70. My brother bought a 83 GMC C.C. dually with a 12 valve and TF727 and 4.11s max speed was about 57mph.

Ohhhh, good point. I hate diesels (at least early GM diesels) so I don't spend much time in them to think about stuff like the lower redline. I solved the diesel problem in my HD by giving it a Vortec 7.4. It's got 4.63's in the rear, can you imagine that with a 6.5TD? Think about the optional 5.13's you could get in a 3500HD at that time!

Richard

Thanks guys for the responce's. I'm looking for a set of 373's now and the stock gear is 410 gears with no o/d. My tire's are stock size on alcoa 16 in rim's so going bigger won't do lol. Again thanks for the help.

I have done quite a bit of research on these as well and from what I understand is the gear set is the same from 70's/80's on up as long as you get them for the same rearend as yours. I used to have a website that showed the rear diff covers and you would match yours up to tell you exactly which ones you have but I no longer have the link. as I remember my 2000 has a 14 bolt full floater. The gears aren't all that expensive but intallation is the killer, unless you have the correct tools I wouldn't suggest doing it on your own. There is a bunch of alignment that needs to be done or you can fk them up quickly. Your best bet is to take it to a shop that specializes in it. Most shops up here don't do it, the only one around is a heavy truck place that specializes in rear ends and driveshafts, etc.

There was an article in one of the truck mags a few years ago on this, can't remember which one though. I have a copy of it somewhere but not sure where it is.

I think FF14 bolts are the easiest axle to set up gears in. Hardest part is setting up the pinion preload with the crush sleave. If you can rebuild a motor you can build a FF14 Bolt fo sho.