Need advice on gearing.

I have posted this in another form but anyhow.
I just got a 76 d30 front end. It has the 6 bolt warn hubs and disc brakes with the 1 1/8 brakes. Nice looking unit. I took off the cover it has 3.53 gears. My rear has 4.88 and is a 30 spline d44. My question is,,, The 4.88 is a little low for what i want to use it for ( beach and a DD). I am running 31s and will stick with them. Is anyone running the 3.53 gears? If I change the rear to 3.53 I guess I will need a new carrier. Please any advice on which way to go? Thanks Eddy

 

I think you would be disappointed in the 3.53 on the beach. If you can regear both axles I would say 3.73 or 4.10s would be a good compromise.

Carrier Split
Dana 44 2.87-3.73 and 3.92-5.89
Dana 30 2.72-3.54 and 3.73-5.38

I run 4.56s and the RPMs get a bit high on the highway even with 35" tires. This is okay for me as this is a trail rig that can be driven on the streets when I need to.

 

I have 3.54s in my pickup and I would have rather had the optional 4.10s. In '71, the two available ratios with a V6 CJ were 3.73 and 4.88, then in '72 Jeep went to 3.73 and 4.27, and in '76 went to 3.54 and 4.10.

Low gearing is good - folks pay big money to get lower gears. I also think you'll be disappointed with the 3.54 gears - if it were my Jeep, I'd be glad that I had the 4.88s and start saving for an overdrive. If you want to install the 30 in the front, change it to 4.88s. You Jeep will be more valuable both with the 4.88s and with the overdrive, so if you ever have to sell, you'll get the most out of it.

 

I'am currently running 3.73s in my cj with 31" tires. I can cruise at 65- 70 mph. kinda pushin it at 70 but have maintained that speed, but 65 easy. Decent freeway speed but still slow for every one else doing 80+. I have a warn overdrive that I havent installed yet but I'm gonna gear lower when I run bigger tires anyway. Hope this helps out with your application.

 

Personally, I enjoy my 4.88's, and pulled down 17.3 MPG commuting last week! This keeps the engine in it's ideal torque range as well. For sand running, I never had a problem out west in places like Glamis, Borrego and the Baja Pennisula. For my $$, I'd keep the 4.88's and save for a Warn OD... My .02

 

Well,, that would be easier to do since I have the D30 sitting in my garage half apart any way. I guess it would work out in the long run. By the time I had someone do the 44 , I could try on my own to regear the 30 and save towards the overdrive. Now to try and find a new carrier and 4.88 d30 gears.

 

eddyt, what's the height of your tires, and how fast do you want to drive on the highway?

 

Here’s a helpful little chart for ya.
Keep in mind that this is showing engine RPM’s at 55 MPH in top gear of a non-overdrive transmission. RPM’s will be higher for 65 MPH and lower, by approximately 20-30%, for an overdrive transmission.

 

Carrier is cheap, about $60 new IIRC. Randy's Ring&Pinion is a good place to start http://www.ringpinion.com/

 

I have 31s and I need to do between 55 and 65. I was looking at the gearing chart. at 55 with the 3.53 it was about 2200rpm and it was 3000 with the 4.88. That is why I was leaning towards the higher gears. But I do not want to give up to much on the beach. And I can not regear both right now.

 

I would go with the 4.88's and get some bigger tires used if you have to. I would not want to run 3.53's. I don't really even like my 3.73's with the 33's I'm running.

My vote is 4.88

High5

 

I calculate (from Novak's gearing calculator) about 2900 and 3400 for 55 and 65, 31" and 4.88s. That's probably a little noisy at 65, but no problem for a V6 in good condition. Also, if you have a GPS, you might check out your actual speed compared to what the speedometer says. If your tires are taller than stock, and you have not changed the speedometer gear, your speedometer will underestimate your speed.

 

I really like my 4.88's, I didn't when I first got my JEEP as I did quite a bit of highway driving. The O/D completely changed my mind and now life is good. Mike

 

Yea your right on the tire size and speedometer. I got out of a ticket because of that one time.

 

The Zj has 3.73s with the 4.0+auto and i can say out on sand at Corova I wish it had a little more umph.
IIRC 4.88s with an OD = about 3.73 with the OD on. Very good compromise.

 

Eddie, I have a 225 with 3.73 gears 31" tires and OD. if you want to test drive, let me know.

 

Randy how do you like them? Heck I would like to meet you and buy you a drink anyhow.

 

the gearing and tire combo is great for street driving, but they render the OD as money I could have spend elsewhere. I want to go to lower gears (4.27)in hopes I live somewhere that the rocks are bigger than a pea and the hills are taller than the interstate some day

as for the drink, gimme a PM close to a weekend

 

Have you taken your on the beach or in some mud yet? And I will do the PM.

 

no sand, light mud. the tires (mud rovers) make short work of mud, and a real mess of the jeepR)