What gear ratio should I get?

[AwesomeJ10]

I'm swapping a 4.3L V6 into my '88 Waggy. It's running a 700R4, Atlas 2sp 3.8, 14bolt rear axle (with disks) and front HP D44. The waggy is my DD (for a 5 mile commute) and isn't 'wheeled very much, but it's going to Ouray in 4 weeks.

I've went over to 4lo.com and used the gear ratio calculator based upon my 34" tire diameter and came up with the chart below.

So what gear ratio should I get? I wanna go as low as possible and thinking about 5.38 gears which means it will be at 2791 rpm's at 75 (which I rarely go 75).

Left column shows the overall crawl ratio at 600RPMs. Second column is axle gears. Third column is with the 700r4 in 4th gear. Fourth column is with the 700R4 in 3rd gear. Last column shows the stock 727 crawl ratio (with atlas 3.8).

[Stuka]

I really prefer this gear calculator: http://grimmjeeper.com/gears.html

Downside to 5.38's in a D44 is the pinion is SOOOOO tiny. Is your front axle an HP axle? That will at least make it less weak.

[AwesomeJ10]

Thanks for the link

Yeah, it's a ford HPD44. I know that D44 pinion is gonna be pretty small on 5.38's (So is a D60), but the waggy really isn't used much for 'wheeling...

Think the 5.38's will be to low? It has 4:10's now, but the rear D60 is shot and is getting swapped out with a 14 bolt. I grabbed a 14bolt from the yard with a eaton LSD, but it has 3:73's. So no matter what, I"m swapping gears..

[Tad]

Just my experience.
I owned my Willys truck for 20 years, the first 15 I had the stock axles with 5.38's, this was with a sb 350, th350 and 203.
The 700r4 may help you but I was very limited at highway speed except in the 35-36" range.
An axle swap gave me 4.10's and that was still annoying for any trips over 3-400 miles.
I think your 34's, 4.10's and the 700r4 would be a pretty good combo.

[will e]

I have to agree with Tad.

My thoughts:
It's not going to be a wheeling truck and the tires are not big. If you had a stock transfer case I might say 4.56 but with a 3.8 atlas you have a lot of low range, not much need for a high gear ratio for wheel'n

[csuengr]

You also have to remember that with a slush box, the lower the crawl ratio, the harder it is to stop. My CJ has a 72:1 CR and to stop going backwards down a hill, I have to shift into neutral.

[Stuka]

Oh, since I didn't comment on actual ratio's, I say go 4.88. With an overdrive it should put your RPM into a better cruising range, but still low enough to make up for the fact that you have a V6.

[AwesomeJ10]

Thanks guys! Lots of good info in this thread.

[jamesdart]

I'm thinking 4.56.

[adamsclarke]

More importantly, what happened to the TBI 401?

[AwesomeJ10]

I sold the TBI 401 to a guy on craigslist for $700.

It was drinking way too much gas.

[adamsclarke]

Well, in that case...I vote 5.3 or 6.o, so when you sell it, I'll be in line with $$$$$

[AwesomeJ10]

So I've completed the 4.3/700r4/atlas swap into the waggy. It's currently on rear D60/Front D44 and 35's on 4:10. Needless to say, it's a dog and needs lower gearing. Now my J20 has the exact same drive train, but small 28" tires and it runs GREAT! Nice and zippy, no problems.

So my delima is that a full set of gears/bearings/shims/etc are about $850 shipped from Randy's R@P. The ratio doesn't matter on the price.

CSUENGR talked about the potential braking issue with low gears and I definitely understand, appreciate and can deal with that.

My shopping cart on Randy's R@P has all 5:38 stuff. So who can talk me out of the 5:38's? Anyone ran those gears on 35" tires and an OD auto tranny and then regretted it?

[Stuka]

So your J20 with 4.10's and 29" tires would be the same as 4.88 with 35" tires (20rpm difference). But 35's also weigh more.

I know a lot of guys with 07-11 4dr JK's (Similar power, weight, and trans gearing) with 35's and almost all of them go for 4.88 or 5.13. I know two guys that have gone with 5.38's. Both of them are very happy offroad and onroad. The deep over drive of the 42RLE (.69, nearly the same as the 700R4's .70) makes cruising nice. And it will stay in over drive rather than constantly shifting out.

You would actually be running fewer RPM than my JK with 4.56's and 33's (2500rpm at 65). My J10 doesnt have OD so its at nearly 3000 at 65. It is NOT freeway friendly.

Just be sure your drive shafts are in good shape. They will be spinning a lot of RPM. But I doubt you will be unhappy with that selection.

[AwesomeJ10]

Yeah I know it's a different thing, but lots of 'cruiser guys over on the mud site are running 285's and 5:29 and seem happy with that. If I were smart, I'd gear the lexus and scrap the waggy....

I think I"m gonna pull the trigger on the 5:38's on Monday after thinking about it over the weekend.

Of course I could always yank the 14 bolt out of Honcho and slap it in the waggy. It already has 5:38's and would be a good experiment...

[Stuka]

Would save you some money to see if you like it. Except you would need to then weld perches on and shock mounts and everything else.

[carnuck]

5.13 will match the other truck

[AwesomeJ10]

Well I'm 100% complete with the engine swap and I was able to take it up to the hills for a little test run.

The main problem is overheating. I have two crappy fans that are not doing a good job. I definitely need to address that before trying to 'wheel in Ouray.

The other problem is power. I did some data logging and found that it's running pretty lean. I have some questions regarding the TBI that I'll post up.

I'm thinking about calling Randy's ring and pinion and talking to them about some 5:13's or 5:38's this morning....

[AwesomeJ10]

5.38's ordered.

Now I have the lovely task of swapping in the 14 bolt this week....