Author Topic: Expedition Build -duals, or is a 4.7 gearset in the case ok?  (Read 1866 times)

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  • Offline Rock Crawl'n
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So here's my plan; if it's stupid just say so! I want to run my little 31" AT tires as a DD, but for off-road, i will install 36" TSR's. Question is, will the crawl ratio with a 4.7 transfer case be sufficient for general exploring out here in the desert (don't plan on running John Bull or technical trails), just stuff like Bradshaw Trail, Fish Creek Canyon and general trail riding. According to the chart, the 4.7's will give the 36" tires about the same crawl ratio as the stock 2.8 with 31" tires. So, i could then have the best of both worlds (75 on the freeway, and still workable off-road). It is a lot of work to change the wheels out, but i don't wheel very often. I suppose if i ran 5.29's, duals and also 4.7's in addition to the 2.8 stocker, i could just run the 36's all the time, but gas mileage would be worse, right? Thanks for input/ideas. -tom
84 4Runner 63's RUFs 36" TSLs 5.29 Frt Aussie
300m Birfs and Hub Gears Full Detroit Rear


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When you change to larger tires, you change the ratio in your rear end and Front diffs. It keeps your Speedo and fuel correct.  Most overland( that is what I think you mean by "Expedition". ) vehicles run about a 33' tire. 

Use the calculator and find the right tire size, and pinion ratio .


  • Offline The 2K Group
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The purpose of running dual cases or a single case w/4.7's is to actually reduce your crawl speed, allowing you to idle over obstacles, up onto/off of ledges, etc., reducing your risk of damage, not as a replacement for correct diff gear/tire sizes.

Based on what your needs of a DD/expedition rig and where you will be wheeling it, I would run 33 AT's, good highway mpg's and work well enough off road, and w/4.88 gears, you would have stock mpg/performance.  I would then run dual cases with either stock 2.28's, or 2.28 and 4.70, I currently run dual 2.28's, and usually find myself needing a little lower gearing from time to time.
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'91 Blue X-cab 22re, 35's/5.29's,Truetrac front, ARB rear, dual cases, and custom Safari flatbed, bumper, interior.
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  • Offline Rock Master
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The reason dual cases is great is the options it gives you.  You want the slow and control that comes with lower gears like snowtoy said, but often when people run a single 4.7 case they find the gap between high range and low range to be too much.  High range is too high and low range is too low for most obstacles.  With a the dual case, you maintain that factory low range to help bridge that gap for easy trails. Like Snowtoy said the best way to go is a "Dual Ulitmate Case" (2.28 front case, 4.7 rear case).  Marlin calls this the ultimate because it really is.  You maintain your factory low, you have the 4.7 for harder areas, and double low for when you really need to get technical.  Overlanding/ Expedition is going to put all kinds of scenerios in front of you, and having the dual ultimate, you will never be wishing you had a different ratio, because all the options are right there.
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  • Offline Rock Crawl'n
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Although new to the toy scene, I DD my 1st gen runner, 5:29's 35 inch tires(MT) bumpers winch, full cage and getting about 17 MPG with a stock 22RE with cold air intake, performance muffler(no cat)

flhtom [OP]

  • Offline Rock Crawl'n
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17 mpg is pretty good, for running bigger tires; i get about 15, on a good day, with the little skinny 31" BFG A/Ts. So, i think the 4.70s in orig. transfer case and original rearend ration(4.10) will allow me to run the 36" TSLs offroad, and still run the skinny tires for best daily driver mileage, plus; it will still be able to commute at 70 mph. i do see dual cases in my future, 'tho! when i dual case it, i will install the 5.29s (no more 31" tires). Thanks for replies, guys.
84 4Runner 63's RUFs 36" TSLs 5.29 Frt Aussie
300m Birfs and Hub Gears Full Detroit Rear


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The issue will be getting to the trail with 4.10s and 36 tires. I gave up on 4.10 gearing in my 85 when I went to 33 tires.

4.88 gears with 33 tires is a great overall solution. Get the BFG 33x9.50 if you want a skinny.
1989 4Runner: Dual Ultimate (Inchworm front & Marlin 4.70 rear), Marlin Twin Stick, 1200-lb clutch, 4.88 R&P, Aussie Front, Detroit rear, 30-spline Longs, Long hub gears, ARP hub and knuckle studs & 35x12.50 Cooper STT PRO tires.  Marlin rear bumper & sliders.  FROR front bumper.  SAS with Alcan springs & Rancho 9000XL shocks.  Budbuilt Bolt-on traction bar.  Custom Interior Cage by Those Guys Rod and Customs.

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I agree with BD. if you or someone you know can set up a 3rd member, ditch the 4.10s and look into 4.88 gears.
:)bestgen4runner [12:45 PM]:   I am so stupid.

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  • Offline Rock Crawl'n
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I would go with the consensus and regear for 33s first. Duals are a great extra tool to use in a rig, but my opinion is unless your rig lives in the rocks I would regear first.
Naturally a realist, preferably an optimist.


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