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Gear upgrade

M

mcweenie

NAXJA Forum User
Location
Banning, Ca.
I have an 89 XJ that I'm putting a Rusty 6.5" long arm kit and 33" tires. It has stock D35 & 30 axles and I'm upgrading the rear to D44 Leaving the front at D30 for now. .
My use is Modertate crawling and weekend recreation...

My question is what is the lowest gears that I can get with a frt D30 and should I go the lowest or stay a bit higher?


Any thoughts or suggestions?
 
To be honest I havent checked on whats in it now, just know I dont want them. I'd like to go 4.88 or lower if possible, but I havent found info on it yet in our forums.
 
Oh well I forgot to mention: I have ARB lockers on a 74 CJ that got totalled, with 4.27 gears with the same axle set up. I was planning to use the lockers with lower gearing if it will work, if not then possibly just use the 4.27 gears out of the CJ if necessary but I'd like to go lower if possible.
 
mcweenie said:
Oh well I forgot to mention: I have ARB lockers on a 74 CJ that got totalled, with 4.27 gears with the same axle set up. I was planning to use the lockers with lower gearing if it will work, if not then possibly just use the 4.27 gears out of the CJ if necessary but I'd like to go lower if possible.
Click to expand...
Your lockers will work with 4:88. Go for it.
 
VAhasnoWAVES said:
the 44 can go lower than, 4.88. the 30 cannot. i wouldnt go lower than 3.56, 4.88 unless you want to get bigger tires. with that lift... i would.
Click to expand...
i think he means 4.56 because the d30 ring and pinion get extra weak when you go lower than 4.56
 
When I wear out these 33's I will likely go bigger... my tires are still new so i'll be running them for a while. When they do I dont want to replace gears regretting my gears i chose now.
 
mcweenie said:
When I wear out these 33's I will likely go bigger... my tires are still new so i'll be running them for a while. When they do I dont want to replace gears regretting my gears i chose now.
Click to expand...

4.88 maybe alittle low for 33's, not sure.
You nailed it-better to change tires than gears.
I made that mistake!
Still at 4.10's and 32's-this will change with time and money.:laugh2:
 
88xj 4.0 31" said:
i think he means 4.56 because the d30 ring and pinion get extra weak when you go lower than 4.56
Click to expand...


There is no actual evidence to support 4.88's being weaker. If you do the research, as many 4.56 gears break as 4.88's do.


4.88's and 33's while it sounds low really is not - it works out great. The 4.0 has no problem running down the highway at 3,000 RPM's all day but hates to pull hard - it will do the job, but drinks the gas. 4.88 with 33's or 4.56 with 32's is more perfect than you can imagine.
 
I've run both 4.56's and 4.88's with 33" tires and the 4.88's are better. The 4.56's were great with 32's. As far as gear strength, it's a matter of tooth count and contact patch with the various ratios, numerically higher isn't necessarily weaker. Some higher ratios are stronger than some lower ratios. Basically, forget about gear strength and just run the gears you want. People talk about gear strength but nearly everyone is just repeating what they've heard on the internet, very few really know.
 
I love my 4.88s and 33s. 70mph equals out to around 2700rpm, 75 is 2800ish. The engine handles the rpms fine, and I see no need to be trying to do 85-90 like some.
 
Goatman said:
I've run both 4.56's and 4.88's with 33" tires and the 4.88's are better. The 4.56's were great with 32's. As far as gear strength, it's a matter of tooth count and contact patch with the various ratios, numerically higher isn't necessarily weaker. Some higher ratios are stronger than some lower ratios. Basically, forget about gear strength and just run the gears you want. People talk about gear strength but nearly everyone is just repeating what they've heard on the internet, very few really know.
Click to expand...
It makes sense to me that the higher ratio gearsets would be stronger from the standpoint that the lever arm of the pinion teeth is shorter thereby reducing stress on the head of the pinion. However, if there is much less contact area of the teeth then more stress is applied to each tooth. I think it's basically a wash.
 
jeeperjohn said:
It makes sense to me that the higher ratio gearsets would be stronger from the standpoint that the lever arm of the pinion teeth is shorter thereby reducing stress on the head of the pinion. However, if there is much less contact area of the teeth then more stress is applied to each tooth. I think it's basically a wash.
Click to expand...


When I built my dana 30, I spent about four days reading up here. I found 4 4.88 gearsets that had died and 6 4.56. I think the 4.88 guys were a little more careful based on the myths, but in general I don't believe there is any difference in strength.

But I'll admit, there may be someone out there who did more dana 30 research than I did. God help him. ;)
 
As to the carrier break, I got a brand new 4.10 up from randy's for $65 when I did my swap. I have 4.88's with 35's and they are about perfect. I'm seeing about 14% lower than stock once tire size is factored in.
 
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