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grininmonkey 12-21-2011 09:42 AM

Looking for some advice!
 
So I finally have a few bucks left after x-mas shopping, not much but enough to finally do something for my poor little jeep.

I've been riding around for more than a year with a 3.73 ratio and 31" tires which is under geared by a good .40th of a turn.

I also have a dropped Transfer case to correct vibrations from my 2.5" lift. So I have an awful looking shovel hanging down an extra inch from the frame.

I want to correct both but I can only really afford one of the two following options right now.

  1. 4.10 gear set for front and back and a POWERTRAX no-slip locker for the rear.
  2. SYE kit, CV extended axle and POWERTRAX no-lip locker for the rear.

If I take the time to open my diff for a locker install... I would like to go ahead and pull the carrier and change my gears in one shoot....

But that shovel hanging down so low, realy... really annoys me to death.

If it's going to be a little while before I can do the SYE and new shaft... am I better off getting back my torque and milage with the gear replacement.. or should I move now on the SYE ?

I hate choices sometimes!

Jason 12-21-2011 11:31 AM

Remember you'll also need adjustable rear control arms (at least uppers, but all 4 would be better) to go with the SYE/DC driveshaft. Keep that in mind while calculating cost. Without them, you can't set the pinion angle.

2.5 spacer lift is pretty small. Have you considered a MML to help with the angle of the t-case output? Perhaps you could get rid of the t-case drop, and do your gears.

The carrier break is 3.55 / 3.73 (D30) and 3.31 / 3.55 (D35) on those axles; you already have the carrier required for the numerically higher gears. The powertrax doesn't require the carrier to be pulled out (based on their instructions). So you could re-gear now and add the locker later without setting up gears again.

Also consider the strength of the Dana 35. You may want to consider other supporting upgrades of you want to lock it (shafts and c-clip eliminator).

Also, re-consider your gear selection. 4.10s still put you under 2000 RPM at 65 in overdrive. 4.56 or 4.88 would be much better, especially if you do any offroading. 4.88s would put you right around 2400 RPM at 65 in OD. Mine runs about there (3.73, 33s, manual trans), and I feel its not enough RPM.

grininmonkey 12-21-2011 11:48 AM

Quote:

Originally Posted by Jason (Post 12718984)
Remember you'll also need adjustable rear control arms (at least uppers, but all 4 would be better) to go with the SYE/DC driveshaft. Keep that in mind while calculating cost. Without them, you can't set the pinion angle.

2.5 spacer lift is pretty small. Have you considered a MML to help with the angle of the t-case output? Perhaps you could get rid of the t-case drop, and do your gears.

The carrier break is 3.55 / 3.73 (D30) and 3.31 / 3.55 (D35) on those axles; you already have the carrier required for the numerically higher gears. The powertrax doesn't require the carrier to be pulled out (based on their instructions). So you could re-gear now and add the locker later without setting up gears again.

Also consider the strength of the Dana 35. You may want to consider other supporting upgrades of you want to lock it (shafts and c-clip eliminator).

Also, re-consider your gear selection. 4.10s still put you under 2000 RPM at 65 in overdrive. 4.56 or 4.88 would be much better, especially if you do any offroading. 4.88s would put you right around 2400 RPM at 65 in OD. Mine runs about there (3.73, 33s, manual trans), and I feel its not enough RPM.

I'm leaning towards the SYE, Gears and no Locker now... I just feel bad that every time I can get a locker I don't... But I guess it might be better because I never know what I may or may not can do with the axles down the road. If I spend 500 bucks re-gearing both my axels and end up replacing the rear with a ford 8.8... I only wasted 250 bucks on the D35. But Like you said... if I do end up keeping the D35, then the powertrax option is simple.

I tried a 1" spacer MML before dropping the T-Case... the vibes were reduced, but still there so I opted to drop the T-Case and removed the MML just to be on the safer side.

I have cam bolts for my rear upper mounts... I wonder if that will be enough to get the right pinion angle after a SYE install?

Jason 12-21-2011 11:56 AM

Quote:

Originally Posted by grininmonkey (Post 12719083)
I have cam bolts for my rear upper mounts... I wonder if that will be enough to get the right pinion angle after a SYE install?

That's not enough adjustment. You basically point the pinion at the t-case output.

If you are only spending 500 bucks to gear both axles, do you want to do mine while you're at it? I think I have over $500 just in parts on my rear.....

grininmonkey 12-21-2011 01:58 PM

Quote:

Originally Posted by Jason (Post 12719126)
That's not enough adjustment. You basically point the pinion at the t-case output.

If you are only spending 500 bucks to gear both axles, do you want to do mine while you're at it? I think I have over $500 just in parts on my rear.....

LOL... Sure but you might not want the brand ;-)

I'm going with the basic Motive Gear kit... http://www.roughcountry.com/gears/je..._3035410M.html

And renting the tools I need from here: http://eastcoastgearsupply.com/i-131...l-program.html

I'm in the lower SC area, 90% mud and sand... the biggest hill might be the bump stop a a walmart parking lot. So I feel like that kit should be at least better than the stock gears and do me ok ?

Jason 12-21-2011 02:43 PM

Quote:

Originally Posted by grininmonkey (Post 12719795)
LOL... Sure but you might not want the brand ;-)

True, I went with Dana Spicer components for mine. And I paid for it. But I have OEM components, which makes me all warm and fuzzy inside.

I strongly considered purchasing that bearing puller, but instead went with a cheapo bearing splitter because I have a press. I managed to pull some carrier bearings without destroying the cages this week. Probably just luck.

The gears themselves are likely fine. I still think you should consider a different ratio since you're going to the trouble. http://www.grimmjeeper.com/gears.html Use this to see where you'll end up speed vs. RPM with different configurations.

grininmonkey 12-21-2011 03:02 PM

Quote:

Originally Posted by Jason (Post 12720039)
I still think you should consider a different ratio since you're going to the trouble. http://www.grimmjeeper.com/gears.html Use this to see where you'll end up speed vs. RPM with different configurations.

With my 31" tires... at 65 mph with 4.56 would be 2217 RPMs... that seems a tad high?

But that leaves room for 33s which I wouldn't mind getting sometime in the next year....

Jason 12-21-2011 03:21 PM

Quote:

Originally Posted by grininmonkey (Post 12720137)
With my 31" tires... at 65 mph with 4.56 would be 2217 RPMs... that seems a tad high? .

I'm the opposite; it seems low to me. I haven't driven mine in two months (snow :brickwall), but I believe I turn about 2400 in top gear at about 70 mph. (33s/3.73/manual) No power. I'm putting 4.56s in right now, (literally, like right now) which should put me a little under 3000 RPM on the highway in top gear. :eek: I considered 4.88s for a while, and if I ever had plans of 35s I would have done it. You may want to think about it if you plan 33s.

Peak torque is at 3200 RPM, max volumetric efficiency at like 2900 or something (I forget exactly, but its around there). You have to compensate for those larger tires too. That motor will run all day at 3000 RPM.

Bottom line, if it were me, I'd go with 4.88s right off the bat because that's as deep as that axle will go. If you had a Rubi, I'd say 5.13 if you thought about 33s.

Jason 12-21-2011 03:33 PM

But don't take it from me. Here's another discussion on the 42rle and gears vs. tires.

http://www.jeepforum.com/forum/f96/w...-video-964113/

grininmonkey 12-21-2011 05:58 PM

That's a good read... all though I'm in a very flat area I can still see some benefit with running 4.88 when I hit the mud. My 42RLE has givin me no issue but I have experienced some under powering in the mud... where I usually stop spinning long enough for the 1st gear to kick in so I have a better torque or umph factor to bounce out of a rut or what not.

I just wonder what the gas milage hit will be for my daily commutes... since I am on flat roads.. will crusing at 2200 rpms be real bad compared to what it is today. Which I average 17.6mph using 87 octane.

Jason 12-21-2011 06:28 PM

Fuel mileage is hard to estimate... Let's say you turn 1800 now. The engine isn't turning as many RPM, but isn't in it's powerband, so it may be working harder (you have to give it more gas to maintain speed). Furthermore, if you have to give it a little more gas for some reason (hill, whatever) it ends up shifting to 3rd and you're now turning more RPM. (Did you see the video? A little extreme, but you'd get the point.) Then you lift with big tires and wheels, that adds weight and wind resistance; engine needs more RPM to work efficiently. When you start turning higher RPM, yes the engine spins faster, but you get more efficiency because the motor doesn't work as hard to motivate the weight.

I will say 17+ MPG is pretty respectable. I get 15-16 now (I think, I'd have to check my receipts). Best ever was 20 MPG all highway with the hardtop and the stock 30s. I expect to get better mileage when I get the gears in. I wouldn't be supervised if you got better mileage with new gears, but there are too many variables for me to make any guarantees. (I wouldn't want to be wrong. :( )


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