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Unread 05-02-2013, 08:37 PM   #1
USFORCES
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2004 WJ 
 
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4.56 gears on the highway?

Right now it's stock 3.73, I'm getting ready to pull the trigger on some new 4.56 gears to go with the 33" tires, anyone know how will it do or how much of a difference on the highway in overdrive doing 65Mph+ they will make?

Also anyone using the IRO WJ Front Chromoly/U-Joint Axle Conversion?

http://ironrockoffroad.com/Merchant2...egory_Code=WDT

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Unread 05-02-2013, 10:34 PM   #2
780406jeeper
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This is the exact gear I am running, and I love 'em. It puts me a few hundred rpms higher than stock with the 235/65r17's, I now have 285/70r17's. It tows my camper trailer much better, and the street performance is a whole lot more fun. Hope this helps. I am a Limited 4.7 non HO.
Kevin
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'78 Cherokee Chief: 360/TH400/NOS QT, '04 Grand Cherokee: 4.7/545RFE/242HD w/SYE, JK Rubi front axle, 4.56 gears, Protofab rear bumper/tire carrier
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Unread 05-02-2013, 10:45 PM   #3
USFORCES
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Thanks for the reply, guess I'll order them up then I was told 285's and 4.56 is a good combo but didn't know how highway use was. Another thing Did you replace the gears yourself? Because I was wondering if I have to have it done by a pro so I don't get any gear wine.
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Unread 05-02-2013, 11:38 PM   #4
85IrocZ-28
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Make sure they follow Dana specs for the "Dana44HD" when they install the rear gears. The tolerances are unique, and need to be followed closely.
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Unread 05-03-2013, 12:07 AM   #5
Relax_Jimmy24
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Wj

Quote:
Originally Posted by 780406jeeper View Post
This is the exact gear I am running, and I love 'em. It puts me a few hundred rpms higher than stock with the 235/65r17's, I now have 285/70r17's. It tows my camper trailer much better, and the street performance is a whole lot more fun. Hope this helps. I am a Limited 4.7 non HO.
Kevin
do you know what ur rpms are at 70mph?

right now i have 32" tires with the stock 3.73 and at 70 am at 2300
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Unread 05-03-2013, 12:52 PM   #6
780406jeeper
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To the OP,
I had a local gear guy do them. Specs are specs, but in the end, the pattern obtained will dicatate noise or the lack of. A seasoned gear installer will ensure a quiet set of gears. Assuming the setup is within specs, fine-tuning the pattern will make the difference. Mine are Yukon 4.56's installed with original carrier and pinion bearings, no noise at all.

As for rpms, it is important to compare apples to apples. So lets start with stock assuming a couple things, V-8 = 545RFE so a 0.67 final overdrive ratio and 3.73-1 axle gears. Stock tires are 235/65R17 tires so an even 29" diameter according to most tire manufactures.
29" tire, 3.73 gears, 0.67 OD, 70mph = 2027 rpms.
31.7" tire (265/70R17), 3.73 gears, 0.67 OD, 70mph = 1854 rpms
33" tire (285/70r17), 3.73 gears, 0.67 OD, 70mph = 1781 rpms
33" tire, 4.56 gears, 0.67 OD, 70mph = 2178 rpms (151 rpms more than stock)

The WJs take their speed signal from the tone ring on the rear axle shaft. Gear ratio has no effect to the speedometer, only the tachometer. So as we go from a 29" tall tire (719 revolutions per mile on tone ring), to a 31.7" tall tire (657 revs/mile on tone ring) our speedometers read 8.6% slower than actual speed. So if you are showing 70 mph on your speedometer (assuming no electronic reprograming) you are actually traveling 76 mph. Plugging in an actual speed for 31.7" tire, 3.73 gears, 0.67 OD and 76 mph = 2013 rpms. This will continue to hold true for a 33" tall tire (630revs/mile for tone ring) equalling a 12.3% difference in true speed. So if you speedo shows 70 mph with the 285/70r17 tires, you are actually traveling 78.6 mph. Hope this all helps.

For what it is worth, I love my 4.56's and find the taller and higher the jeep goes, my sustained freeway speed goes down, but only because of my head. The fuel mileage drops because of rolling resistance and increased wind resisitance so I find myself slowing down a little to accomodate it. If I didn't care, the jeep's V8 wouldn't either. It'll hold whatever speed I want. As I mentioned earlier, the biggest difference has been towing my 19-foot Heartland MPG camper that weighs about 3200lbs wet.
Kevin
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'78 Cherokee Chief: 360/TH400/NOS QT, '04 Grand Cherokee: 4.7/545RFE/242HD w/SYE, JK Rubi front axle, 4.56 gears, Protofab rear bumper/tire carrier
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Unread 05-03-2013, 01:00 PM   #7
780406jeeper
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Relax Jimmy24,
one last thing, not sure if your 2001 WJ has the 45rfe 4 speed tranny program or if it has the 545rfe 5 speed program. If it is the 45rfe program, you only have a single overdrive ratio of 0.75-1. In that case, here are your numbers...

31.7" tall tire, 3.73-1 gears, 0.75 OD, 76 mph = 2254 rpms.
If you changed to 4.56 gears here is what it is again assuming the 45rfe program.
31.7" tall tire, 4.56 gears, 0.75 OD, 76 mph (70 on speedo) = 2755 rpms.

Hope all this helps.
Kevin
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'78 Cherokee Chief: 360/TH400/NOS QT, '04 Grand Cherokee: 4.7/545RFE/242HD w/SYE, JK Rubi front axle, 4.56 gears, Protofab rear bumper/tire carrier
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Unread 05-03-2013, 01:06 PM   #8
USFORCES
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Thanks for the extra info buddy
I ordered the 4.56 gears today. Another question how much did the local gear guy do them for? I'm pulling the rear axle to weld a truss on then replacing the bearing and seals while I'm at it, not to mention one front seal leaks a little.
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Unread 05-03-2013, 01:11 PM   #9
780406jeeper
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My guy is a former gear guy from 4 Wheelers Supply here in Phoenix AZ, one of the oldest 4 wheel drive shops here in town. He charged me $200 for the gear work per axle and that was with me removing the rear end completely, removing the rear axle shafts, and taking him the housing, diff and new gears. He has geared all three of my jeeps. I had asked about the 44hd after reading so many noisy gear posts, and he was well aware. He was the one that told me that on the 44hds, the final pattern (read with marking compound) is what will make or break the noise issue on these. At the same time, he re-geared the JK Rubicon 44 I swapped in to 4.56 as well. Both axles are super quiet.
Kevin
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'78 Cherokee Chief: 360/TH400/NOS QT, '04 Grand Cherokee: 4.7/545RFE/242HD w/SYE, JK Rubi front axle, 4.56 gears, Protofab rear bumper/tire carrier
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Unread 05-03-2013, 02:25 PM   #10
Relax_Jimmy24
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ohh alright yeah I have the 45rfe.
How do I program my tranny to get the 5th gear?
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Unread 05-03-2013, 02:33 PM   #11
780406jeeper
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"ohh alright yeah I have the 45rfe.
How do I program my tranny to get the 5th gear? "

Just gotta take it to a dealer and they can do it for you. Cost a little but most say it is worth it.
Kevin
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'78 Cherokee Chief: 360/TH400/NOS QT, '04 Grand Cherokee: 4.7/545RFE/242HD w/SYE, JK Rubi front axle, 4.56 gears, Protofab rear bumper/tire carrier
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Unread 05-03-2013, 03:13 PM   #12
780406jeeper
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Talked to my buddy that just had the tranny re-flash to 545rfe done at local dealer and the cost was $119.00. He has a 2000 non-HO V-8. He loves it.
Kevin
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Unread 05-03-2013, 07:25 PM   #13
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I'm looking to do 4.56 soonish here too, for 35's I think. maybe I should do 4.88's then? hmmm most people seem happy on 4.56's and 35's though, and a lot of people run stock gears
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