Forum advice vs shop advice: Are 5.38 gears to low for Dana 44?

[Jerry Bransford]

I keep reading what you’re saying Chris, but I also don’t want to offend the guy. I went in there and told him I wanted 5.38 and it went from there. I don’t have mechanical experience so I need a relationship with this shop.

It's not just Chris recommending 5.38 gears. It's completely clear your guy absolutely has no clue on what gearing works best for the 42RLE transmission and 35's, stop listening to his whining and just tell him to install 5.38 gears and to shut up about it. Too many of us are happily running 5.38 gears and NO they do not run too hot, he's just talking through his *** on that. 5.38 was extremely and thoroughly tested before being brought out by several very high-end gear companies including Revolution Gear and Yukon who both are having Circle K manufacture them. Circle K is the best gear manufacturer in the world at this point, there are none better. So don't worry about "offending" that shop guy, just tell him what you want and that you want 5.38 gears without further argument. I certainly wouldn't have gone with 5.38 if I had any qualms about it not being able to hold up without problem to lockers and the big rocks I enjoy crawling on.

Again, stop worrying about offending him, he just doesn't know what he's talking about where 5.38 gears are concerned. And even 5.38 is barely enough for 35's with the 42RLE transmission. I went from 4.88 which was lugging my engine to 5.38 which even improved my mpg by just over 2 mpg due to it having stopped the engine from lugging. But as just said, even 5.38 is barely adequate... I even would have gone one ratio lower than 5.38 if it was available.

One final repeated comment... do not worry about offending that guy. Just tell him to shut up and install the 5.38 gears or you'll find a different shop to install them. Really.

 

[Rob5589]

Gearing should be determined by the type of driving you will be doing mostly. I have the 42 RLE w/35’s and 4.88 gears because I live in Texas and need to be comfortable driving 80 plus miles an hour for long periods of time. If you live in a hilly area there’s no way I would go with a 4.88 ratio, you would simply be searching for the right gear constantly. I know a few people that run 5.38’s with the same setup as me and they Love it other than having to take the slow lane on the highway. When I swap out my axles for 60’s I’ll probably go with 5.13’s to find that happy medium. Get what’s going to suit your style of driving and the terrain you’ll be driving in. That’s my .02 cents worth :beer-toast1:

You can run 80 with 5.38's no problem. The 4.0 can cruise at 2900 rpm all day without issue.

 

[Jerry Bransford]

Gearing should be determined by the type of driving you will be doing mostly. I have the 42 RLE w/35’s and 4.88 gears because I live in Texas and need to be comfortable driving 80 plus miles an hour for long periods of time. If you live in a hilly area there’s no way I would go with a 4.88 ratio, you would simply be searching for the right gear constantly. I know a few people that run 5.38’s with the same setup as me and they Love it other than having to take the slow lane on the highway.

What are you smoking? My 5.38 gears with 35" tires and 42RLE transmission produce 2650 rpms at 70 mph. For 35's at 70 mph, even that rpm is barely adequate on the highway. I'd actually like it to be a 100-200 rpms higher. When I ran a 5-speed manual with 4.88 gearing with 35's, it produced 2750 rpms at 70 mph which is an even more optimal rpm for 35" tires.

When I upgraded that 5-speed to the 3-speed automatic with the same 4.88 gears and 35" tires, naturally its rpms got excessive so I did tend to drive in the slow lane. But with my current TJ with its 42RLE, 5.38, and 35" tires, I'll cruise at any speed that is safe including 80-85 mph a few rare instances. The engine was fine at that speed, I just wasn't.

 

[LJJames]

I'm picking up my 05 auto LJR 35's, this week. Just had 5.38's put in! Yeah baby!! I'll update soon as I've only had it a year, on 4.10's.

 

[Powdermonkey]

It's not just Chris recommending 5.38 gears. It's completely clear your guy absolutely has no clue on what gearing works best for the 42RLE transmission and 35's, stop listening to his whining and just tell him to install 5.38 gears and to shut up about it. Too many of us are happily running 5.38 gears and NO they do not run too hot, he's just talking through his *** on that. 5.38 was extremely and thoroughly tested before being brought out by several very high-end gear companies including Revolution Gear and Yukon who both are having Circle K manufacture them. Circle K is the best gear manufacturer in the world at this point, there are none better. So don't worry about "offending" that shop guy, just tell him what you want and that you want 5.38 gears without further argument. I certainly wouldn't have gone with 5.38 if I had any qualms about it not being able to hold up without problem to lockers and the big rocks I enjoy crawling on.

Again, stop worrying about offending him, he just doesn't know what he's talking about where 5.38 gears are concerned. And even 5.38 is barely enough for 35's with the 42RLE transmission. I went from 4.88 which was lugging my engine to 5.38 which even improved my mpg by just over 2 mpg due to it having stopped the engine from lugging. But as just said, even 5.38 is barely adequate... I even would have gone one ratio lower than 5.38 if it was available.

One final repeated comment... do not worry about offending that guy. Just tell him to shut up and install the 5.38 gears or you'll find a different shop to install them. Really.

Thanks Jerry. He installs Nitro, any issues with their gears or axles?

 

[Jerry Bransford]

Thanks Jerry. He installs Nitro, any issues with their gears or axles?

Yes, I don't believe Nitro has 5.38 gears for the Rubicon axles. They need to be thick cut on top of that since the Rubicon's locker is not set up for gearing lower than 4.11 without a thick ring gear.

 

[Andy5150]

It's not a matter of opinion. There's no way 35,s with a.69 overdrive, is turning over 3000 rpm at 70 mph with 5.38 gears, unless maybe the overdrive is turned off.

 

[Chris]

They’re hitting over 3k rpm’s at 70

I was actually hoping to be around 3k RPMs at that speed, so I guess this works out well for me in any case!

 

[jjvw]

From grimmjeeper.com...

34", 42rle, 4.88 = 2329 rpm @ 70mph
34", 42rle, 4.88 = 2662 rpm @ 80mph

34", 42rle, 5.38 = 2568 rpm @ 70mph
34", 42rle, 5.38 = 2935 rpm @ 80mph

I chose 34" because a 35 doesn't have a rolling diameter of 35".

 

[jjvw]

I was actually hoping to be around 3k RPMs at that speed, so I guess this works out well for me in any case!

You might want to check his math.

 

[Boinked]

Just for an example

BF Goodrich A/T K02
Stated Size on Sidewall - 35x12.50x17
Actual Measured Size - 33-3/4

And try to remember that's going to vary on tire pressure rim width and many many many other things. Trying to nail down an exact RPM at an exact speed for an exact set of Gears needs an exact tire. And tires aren't exact

 

[Jerry Bransford]

They’re hitting over 3k rpm’s at 70

Pure unequivocal bullshit. You may know something about Jeeps but you absolutely don't know WTF you're talking about where gearing is concerned. Period.

2600-2650 is what you get with 5.38 cruising at 70 mph with a 42RLE and 35" MT/Rs. I own and drive that combination regularly with a perfectly calibrated dead-nuts on speedometer.

 

[jjvw]

3rd gear would put their 70mph at 3376 rpm, which means the Texans are probably shutting off the OD and not telling anyone. This is more evidence that they ought to regear to 5.38.

 

[jjvw]

...

I have only done what I would consider easy trails. But living in western Colorado I want to do Holy Cross, Engineer Pass, Black Bear, Moab, the good shit! Im not looking to destroy the Jeep but this thing is going to see trails.

Thanks guys

I know there are others Coloradoans on the forum, but tworley and I both have pretty good Jeeps with build threads. We both daily drive and we are built well enough to tackle most of what is out here. It might be worth the read to see what to copy.

 

[Mike Jolley]

From a pure gear ratio standpoint the 5.38’s match well with a 35” tire behind the 42rle with that tall 0.69:1 overdrive ratio. The 4.0 likes to run in the 2500-3000 range at freeway speeds. Listen to Jerry, speaking from real world knowledge is always better than listening to somebody that makes assumptions. If you plan to wheel it hard you have one other factor to consider and that is gear mesh. The lower the gear ratio the less gear mesh you will have, that’s just the physics of a ring and pinion gearset. Everything else being equal, the 4.88 gears are stronger than 5.38’s because they have more gear surface touching. My rear end builder prefers not to use anything lower than 4.88 in a Dana 44. For 5.38’s you might want to step up to a Dana 60 or something else with a larger diameter gearset. We run 4.88’s in my sister’s TJ rolling on 33” rubber. I was hesitant to go that low with the relatively short tires but it actually does extremely well on the highway. At 80mph GPS on the way to the Rubicon last month she was still turning less than 3000 rpms. Generally too fast to ever drive a lifted TJ but I wanted to see where things went.

(edited to eliminate confusing for high vs low terminology)

 

[Chris]

Interesting, I didn't know the higher gears have more mesh (i.e. 4.88 has more mesh than 5.38). Shows what I know!

 

[Powdermonkey]

From a pure gear ratio standpoint the 5.38’s match well with a 35” tire behind the 42rle with that tall 0.69:1 overdrive ratio. The 4.0 likes to run in the 2500-3000 range at freeway speeds. Listen to Jerry, speaking from real world knowledge is always better than listening to somebody that makes assumptions. If you plan to wheel it hard you have one other factor to consider and that is gear mesh. The higher the gear ratio the less gear mesh you will have, that’s just the physics of a ring and pinion gearset. Everything else being equal, the 4.88 gears are stronger than 5.38’s because they have more gears touching. My rear end builder prefers not to use anything higher than 4.88 in a Dana 44. For 5.38’s you might want to step up to a Dana 60 or something else with a larger diameter gearset. We run 4.88’s in my sister’s TJ rolling on 33” rubber. I was hesitant to go that high with the relatively short tires but it actually does extremely well on the highway. At 80mph GPS on the way to the Rubicon last month she was still turning less than 3000 rpms. Generally too fast to ever drive a lifted TJ but I wanted to see where things went.

Mike you touched on one of the shops big concerns, gear contact. He wanted me to go to 60s but being new to jeeping I want to ensure this is something I will continue to enjoy before dropping 15k.

The shop said he will put whatever I want it’s my money. He will warranty the work, but could tell if the failure is due to install or neglect.

 

[Jerry Bransford]

Higher vs lower terminology is confusing, 5.38 is higher the way I was taught by dad. So in that context higher gears mesh less.

5.38 is a lower ratio than 4.88 is. A lower ratio causes the ring gear to rotate at a lower speed with the same speed at the driving pinion gear which is why it's called a lower ratio.

And a lower ratio doesn't necessarily mean it doesn't mesh adequately for the forces involved. There are plenty of people like me running ratios like 5.38 in our Dana 44 axles on extremely difficult rock crawling trails without problem. They have been well tested on extreme level trails like the Hammers out in Johnson Valley California.

 

[jjvw]

I forget the details, but aren't the RGA 5.xx pinions the same size as 4.88?

 

[Mike Jolley]

5.38 is a lower ratio than 4.88 is. A lower ratio causes the ring gear to rotate at a lower speed with the same speed at the driving pinion gear which is why it's called a lower ratio.

And a lower ratio doesn't necessarily mean it doesn't mesh adequately for the forces involved. There are plenty of people like me running ratios like 5.38 in our Dana 44 axles on extremely difficult rock crawling trails without problem. They have been well tested on extreme level trails like the Hammers out in Johnson Valley California.

5.38 is numerically higher than 4.88... that’s the nomenclature I was taught by dad. Maybe being a stubborn engineer factors in to it too

Another point where Jerry and can agree to disagree.