Gear selection

[Gunnibronco]

It's time I get serious about choosing a new gear set. Let me know what you'd do and why.

37s, 3.50's, ZF5, with a 302 just isn't working on the road. Off road everything is fine with 3 low gear choices (2.7, 4.3, 11.7).

I put together a chart below. I was considering 4.56 because I have a set for the 9". I'm ok not using 5th much. But looking at this, I realized at about 55 mph there is no good gear choice.

My basis is:

2300-2900 RPM is ideal.

2200 RPM is marginal on the low end- I can still accelerate to higher RPMs on hills, below this I can't.

3000 RPM is marginal on the high end- It's ok, but feels like I don't want to hang around or go much higher. Maybe I'm a wimp, feel free to tell me I'm wrong.

[Gunnibronco]

How much of a concern is the strength of gears compared to the gear ratio? I've been told the higher gear ratios are weaker. Is this a real issue? Some of the club members (running big gear ratios and tires) said this is outdated info and not a real big concern.

[B.O.B.]

Don’t really know about for the Broncos but when we do gears at work on the JK’s we tend to stay away on the 5.38 on the d44 because pinions are super small and you only have about 2 teeth touching the ring gear. After looking I will probably do 4.88 with my 37”s here in a bit.

[Jesus_man]

There is some truth to the higher gears numerically. The pinion gets smaller and as Bob said, less steel contact with the ring gear.

Where are you driving the bronco, how often, and what are the speed limits? My vote is likely going to be 4.56, but I see some advantages to the 4.88, especially with a 302.

[Gunnibronco]

Thanks JD & Bobby,

I posted the same question at CB.com and FB.

I've seen some with 4.88s with a similar set up who are happy.

Some with 4.88s who wish they went with 5.13s

I haven't found anyone who regrets 5.13s and wish they went lower.

With my elevation 4700', Sierras at my backdoor (higher elevations and mountain driving), I'm leaning towards 5.13s despite the strength issue. Crawler said he ran low pinon 5.13s for years on 37s without ever breaking gears. I'm hoping my puny 1310 ujoints and/or hubs will be the weak link in the system and keep breakage trail serviceable. I bet with 11.7:1 I can break something in any set up. Chromo axles and CTM Super Joints will go in with the new gears. I'll also be changing from the "weaker" 78/79 housing to an earlier 76/77 housing.