Basic Re-gearing question

[Cruiserdrew]

I don't know that I buy those hard and fast rules MoJ. The 80 has a crawl ratio near 30:1 anyway. That doesn't change much with differential gearing changes. There are too many variables as I see it. For me, the 4.88s seem perfect. Your revs at speed are *slightly* higher than stock. That's a good thing for getting these very heavy tires moving. It's an even better thing for Romer who lives at 5000 feet and climbs passes twice that.

As for crawl ratios, my FJ40 is about 70:1, which seems totally great when compared to stock at 35:1. There have been rare times when an even higher ratio would be desirable. Most of us end up with a compromise of what is drivable and what is economically feasable. 4.88s work with 35's. 4.56's would work too, but I don't know that I'd spend all that $ for just a 10% change in gear ratio.

All of this discussion really begs the question of when Marlin will have a Toybox available for the 80, and really lower low range in a meaningful way.

 

[cruiserdan]

Crawl ratio is less of an issue with automatic transmission vehicles because of the torque multiplication factor in the torque converter. There is no "fudge factor" with a manual, other than a smoking clutchplate....

 

[MoJ]

I don't know that I buy those hard and fast rules MoJ.

Agreed, the author is very direct about the rules not being hard or fast. For instance, you never have 100% traction in the real world, all tires are rarely equally planted, torque varies by RPM, some drive trains have more/less friction, etc, etc. However, it's basic physics and gives you a quantifiable starting point. If someone is trying to determine what gear for what tire they can at least look at the effect various combos have.

 

[fj803fe]

I am a 3fe bastard child-but I run 4.88s w/ 35s and I REALLY notice the difference off road-no more touching the brakes on down hill stretches-in fact I often have to throw her into 2 to catch up w/ the group (Oh yeah-thats right! the fzj doesn't select Low range [e.g. 1st] does it?...).

Crawling has not been a problem and as I posted before, while some 3fe's may die in power at high elevation steep climbs I had no troubles at 11,500 ft.-I would really attribute that to gearing as the high elev toll on the engine was noticeable but not great.

I had everything ready for the gear swap (I was doing ARBs too), bearings, crush sleeve, gears, all needed parts and did my homework as to what bearings would/wouldn't work with the R&P I was putting in-I did take it to Avalanche Engineering here in Durango-the guys were great, basically gave me a crash course in gear install (as I asked if I could help). If I'd do it again-I'd do it myself-but after the lessons I can see I wouldn't have wanted to attempt w/o either having someone VERY knowledgeable on my shoulder the whole time.

I'm then with the rest of the advise given I guess...

 

[ginericLC]

You might assemble it all yourself and then take it to a shop for fine tuning. That is what I've done on more than one occasion. Actually not a shop just a guy who is really good at them. It is both an art and a science. A friend of mine owns a repair facility and I've worked on some rearends at his shop. Mostly semi trucks. Same thing just bigger. I feel like a school kid getting a test when I'm in there.

 

[lowtideride]

I have set up a set of r&p this summer for the first time. After getting all the tools and reading up a bit( not to mention some help from Mace and 2Badfj) it was not all that bad...Just time consuming. To tell ya the truth it was hot enough out that I just brought the 3rds inside and set them up in the computer room. After setting the first 3rd up the second one goes much faster. I also vote 4.88s more than likely you will only want to go up in tire size.

 

[alkaline747trio]

Kinda thread jacking here...but I plan to regear, put on 33's, and get an aussie rear locker this winter. I was curious, with 33's, would 4.88's be too slow to take on a highway trip (70mph, 500 mile trip)? I plan to get lift and 35's this up comming summer, but don't want to have to pay for a new R&P for the 35's after putting in lower gearing for the 33's too. Also, with the 3FE, would 5.26's be better with 35/36's then with 4.88s? I don't do many highway trips, maybe 2 a year (one to the Appalacian mountains, the other to the OBX), the rest of my driving is sub 60mph and around town and trails.

 

[Romer]

Since your jacking my thread

I run 285's (33's) have a 2.5" lift and stock gears and have gone on several long trips with no issues. Worked awesome in Moab and some runs here in Colorado.

If you are going 33's I would not re-gear

Edit: I did not notice you had a pre 93. I don't have a comparison there and will let others chime in.

 

[alkaline747trio]

Yea, I think my 3FE might struggle a little more than your's. I wish I could find someone with a 3FE and 33's around here to see what it is like, just to see if I can deal with it.

 

[cruiserdan]

A 3FE really needs more leg for 33's. I would go 4.88 with 33's and a 3FE.

 

[alkaline747trio]

So would you then suggest 5.26's for 35/36's? Also, would 5.26's be unbearable for 6 months on 33's?

 

[PHAEDRUS]

As much love as I have in my heart for him, I must disagree with Dan, the 3FE with stock gearing is only a dog if you are in a hurry or trying to tow something. Mine has been set up this way for 3 years now and while I wish it would get off the line quicker it is not as bad as you might fear.
FWIW I am planning on going to 4.88 and 35" tires this spring.
Dave

 

[fj803fe]

As much love as I have in my heart for him, I must disagree with Dan, the 3FE with stock gearing is only a dog if you are in a hurry or trying to tow something. Mine has been set up this way for 3 years now and while I wish it would get off the line quicker it is not as bad as you might fear.
FWIW I am planning on going to 4.88 and 35" tires this spring.
Dave

Here here! 4.88s are too low IMO for 33s on the 3fe...just too much RPMs-its got plenty to turn em. the 4.88/35" I have found to be a great combo.

Your off the line with the 4.88s will be just fine-in fact you may actually be VERY impressed...

I actually think 5.29s would be good too-only if the majority of your driving is not highway. The 85 4Skinner w/33s and 5.29s was a killer combo-never got around to installing them on mine (still have em in the garage...anyone???) but drove a couple like this_LOVED IT-but then, I like downright LOW gearing.

The only worry may be (though probably unfounded and purely out of logical worry) that the 5.29s will be pretty weak relative to the higher rings due to the number of teeth on the ring around the smaller radius in the h-p front diff. But, I've only heard this as a concern thrown out in the past when I was looking into gearing for both my 4Skinner and my 80-I could not speak to its validity.

 

[Pskhaat]

Oh yeah-thats right! the fzj doesn't select Low range [e.g. 1st] does it?...).

Listen, the A34? has 3 gear selections plus O/D, so yes, L is basically first. Must be the FJ80 guys must physically see a 1 then?

 

[fj803fe]

Listen, the A34? has 3 gear selections plus O/D, so yes, L is basically first. Must be the FJ80 guys must physically see a 1 then?

No "1" there, but thanks for the info.

I'll file it under my "I don't give a F$#k" section, in my mind.

 

[Pskhaat]

I'll file it under my "I don't give a F$#k" section, in my mind.

Isn't that where you file everything in your mind?

 

[-uhuru-]

Listen, the A34? has 3 gear selections plus O/D, so yes, L is basically first. Must be the FJ80 guys must physically see a 1 then?

that tranny doesn}t have the second start option?

 

[fj803fe]

Isn't that where you file everything in your mind?

maybe.... ;p

 

[ShottsUZJ100]

This was the PERFECT thread for me to read.

I am re-gearing my new LX I just bought. I wasn't sure on the 4.56 or 4.88 though now have decided on 4.88s.

NEW QUESTION: What brand and who should I buy from? Cost for both sets? Do I need "install kits? I'll be re-gearing and adding ARB lockers at the same time. THANKS!

 

[sleeoffroad]

Buy the stuff from the person doing the work. Otherwise you will just create issues. No doubt for a trail rig, you need 4.88's. For the 38's you are going to run, you might even consider 5.29's