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Unread 07-03-2013, 06:40 PM   #1
Unclejimbo
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Another automatic and gear ratio question

My current set up is a 4.0 5spd with 4.10 d30 and 8.8 sitting on 33's. I have an entirely rotted out automatic 95 4.0 which I pulled the entire drivetrain, wiring, column, pedals, etc. I am considering swapping out my ax-15 for the auto and going to 35's. I have been reading for the past 2 nights on which gear ratio to run with an auto and 35's but cant really find a definitive answer. I have a set of 4.88 ring and pinions sitting in the garage for a d30 and the 8.8. I wanna gear it to be decent on the highway and then modify the tcase for offroad. Should I stick with the 4.10's, or use the 4.88's, and then what should I do to the tcase?

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Unread 07-03-2013, 08:27 PM   #2
JBTJ
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I think the 4.88 might be on the high side, but good for intown. 4.56 maybe better for all around use. 4.10 is better for 33's and auto. TC I wouldn't worry about unless you are a hard core wheeler.
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Unread 07-03-2013, 09:10 PM   #3
Unclejimbo
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Yeah the 4.56 is what seems to be the best out of all my reading, however I have a d30 with 4.88 in it already and a 4.88 ring and pinion for an 8.8 that came with the 4.10 one I already have in the jeep, and I was trying not to start over basically. That was also why I thought maybe do 4.10 for driving what highway I do and put some money into the tcase to make up for the gears. I guess from those 2 options would the 4.10 be a good setup for on road and not suck off road? The little chart at grimmjeeper basically says I will be at 2500 ish rpms at 65 which is acceptable and my crawl speed is as follows
1000 rpms 2000rpm 3000rpm
1st 301 ft/min 602 903
2nd 536 ft/min 1071 1607
3rd 825 ft/min 1650 2475

Are those numbers good? I know these are all estimates and such but im trying to learn all this stuff and build a rig that will suffice on road but not suck off road.
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Unread 07-04-2013, 12:06 AM   #4
bill8bud
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Try this calculator out. One big difference between the auto and the manual transmission is the auto is a 3 speed and the manual is a 5 speed.

http://www.grimmjeeper.com/gears.html
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Unread 07-04-2013, 12:16 AM   #5
Tom95YJ
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4.0L

33's = 4.56
35's = 4.88
37's = 5.13
And the list goes on
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Unread 07-04-2013, 07:47 AM   #6
Unclejimbo
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Thats how I got those number was using grimmjeepers calculator. Last the list I generally go by, but 4.88 seems a little steep with 35's and a 3 spd, atleast on the highway, and 4.10 seems ok number wise but im afraid it might be a little underpowered. I reckon I could always do the swap and if I dont like the 4.10's just say screw it and go 4.88.
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Unread 07-04-2013, 12:38 PM   #7
DLWRUBI
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Plenty of guys doing 4.10's on 35's, is it optimal, not really. I ran 4.10's on 33's for 17 years and it's the perfect package with a 5 speed. However, I am now switching to 4.88's with 35's (will go to 37's later) and a 4 speed automatic. If your doing a 3 speed auto, like mentioned, 4.88's will not be as great on highway. Ultimately, I think 4.88's is the better of your options for 35's but I would consider keeping the 5 speed or find a better auto 4 speed to use.
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Unread 07-04-2013, 01:20 PM   #8
Unclejimbo
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At one point I was going to do the aw4 swap but then a buddy told me if I get that 95 auto off his property I could have it, its rotted all to hell but runs great and shifts great, I rode it around in the yard without seats . So in an awesome situation I would like to do the aw4 but seeing as how I have entire donor vehicle and basically two sets of gears to choose from I'd like to use what I got. But I'm not against keeping the 5spd either. Decisions decisions.
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Unread 07-04-2013, 09:05 PM   #9
yellow2kgt
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I recently swapped my 4:10s to 4:88s last fall. I also have the three speed auto and with the 35s the 4:10s were not enough gear. I do live in a hilly area and most of my wheeling trips require a lot of uphill drives crossing a mountain or two. Even with an external tranny cooler I felt like I was really working the tranny. With that said I think the 4:88s are too much gear for a lot of highway driving. I usually cruise the highway at 60. Not because of a lack of power but at that speed my 4.2 is turning close to 3000 rpm and that's as high as I want to turn it for extended times. I would think 4:56s would be ideal but considering my daily commute is about 5 miles on rural roads the 4:88s are perfect for me.
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Unread 07-04-2013, 09:26 PM   #10
Unclejimbo
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Thats pretty much what I thought, sadly the only time im on the highway it ends up being a long haul,mainly for offroading areas and heading to my parents, other than that its just normal road travel.
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Unread 07-04-2013, 11:07 PM   #11
rambo3489
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If your ever going to 35's go with the lower gears. Not sure what the OD ratio is on the auto. But go with the 4.88s. you will thank yourself later.
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Unread 07-05-2013, 09:52 AM   #12
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Its a 3spd auto so no overdrive and I am going to 35's. I think that's the route I'm going I'll just deal with the high rpms on the highway
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Unread 07-05-2013, 11:02 AM   #13
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I will add my .02 in on this even though I am running a 5 spd. I am on 35's with 4.56 gears and I love them. At 70 I am turning about 2300 rpm in 5th gear. Have no trouble going up hills and even with a head wind. I really feel like the 4.56 gears and 35" tires put my jeep back in the factory setting. I know this because when I installed the factory speed sensor, came out of a 95 4.0, AX15 with 3.55 gears, I was running 2mph faster in 5th gear at 70. Personally I think 4.88 with a 3 speed auto may be a little much on the highway. Of course this is just my opinion but thought maybe you would like to know.
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Unread 07-05-2013, 11:17 AM   #14
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Quote:
Originally Posted by Unclejimbo View Post
Its a 3spd auto so no overdrive and I am going to 35's. I think that's the route I'm going I'll just deal with the high rpms on the highway
And 4.56 will be perfect for this setup.
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Unread 07-05-2013, 12:07 PM   #15
Unclejimbo
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I had 4.88 in my 5spd 4cyl and it ran around 3k at 65 or so. Would like to do 4.56 but as stated I am on 4.10 and have the 4.88's so I was trying to find out between the 2 who has ran what and their experiences with it. Just don't wanna shell out the money for an entirely new set of gears and such. Hell who knows it seems 35's are a gateway to 37's or bigger so might just work out
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