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Doubler owners - lets hear your final drive ratio and tire size

M

Mudzer

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I am installing a Dual Transfer Case setup soon and wanted to know how you all have geared your axles and what tire sizes you have.

I currently have 4.10 gears with the SM465 setup and 38" tires. I would assume since I am changing to Auto, the cruise RPM will come up slightly because of the converter. I may swap out to 4.88 gears, but is it necessary in an Auto - Doubler setup with 38" tires? Give me some input.
 
I dont run a doubler, but mine is 36.42:1 wihout the torque conver multiplication. 72.84:1 with. I run a 700r4, 208, 4.56 gears, and 35. I know Marv is within a half a point of mine with his doubler set up. He runs a th350, 203/205 doubler, 3.73 gears and 35s.

Dan
 
Well lets see, th350=2.52, 203=2.01, 205=1.96, 14bolt=4.10

Sooooooo, 2.52x2.01x1.96x4.10=40.7 then multiply that by two for the converter, and thats 81.4 and im running 37s. The higher axel gears are good on the street except for long uphills but with all the gears i can select i still have plenty of grunt off road, Iwould however like to swap to 4.56s for a little more grunt on the street. The biggest avantage for me with the doubler is the ability to run in 2 low so i can steer with a front locker, i usually shift the 203 into low then toggle the 205 in and out of 4 wheel drive, then shove the 205 into low for compound low.
The Biggest disadvantage is that now everybody wants to use me as a guinnea pig, "Dude, put it in low and try it, let us know if we can do it too!"
 
Ha....!..

"The Biggest disadvantage is that now everybody wants to use me as a guinnea pig, "Dude, put it in low and try it, let us know if we can do it too!"


Leland.... be careful...! That's how all those dents got on Ol' Green. /forums/images/icons/smile.gif

Marv
 
465 1st = 6.57, 205 low = 1.96, and diffs = 4.10. All that and I get the crawl ratio of 52.79. If (yea right!) WHEN I install the doubler, that will add another 2.01 step for the 203... getting me to 106.12!!! WOW! That's even more than I expected!

So Neil, when are we making that exchange again?!!! /forums/images/icons/wink.gif /forums/images/icons/laugh.gif The sound of a 3 digit crawl ratio is very cool!!!

-Dan
 
Actually if Marv were to add the same gearing, thats where you would see the major difference in having a doubler or not. I have heard to use between 2 and 2.5 for the torque multiplier for the converter.

Heres the calcs using 2.5 for the torque multiplication:

Dan's 700r4/208 combo with 4.56 gears is 2.5/3.06/2.61/4.56 = 91.05 crawl ratio

Marv's Th350/Doubler combo with 4.56 gears (if he had them) is 2.5/2.52/3.96/4.56 = 113.76 crawl ratio.

Thats a difference of 22.71 which seems like a small amout but it is really alot. Heres a comparo which should make some sense:

The difference in Marv's setup and your 700/208 combo with the same gearing is roughly 23 points. That 23 points equates to 1.12 in numerically higher gear ratio. Now, this doesnt sound like much but it equates to roughly like going from 3.08 gears to 4.10 gears and thats a noticable improvement.
 
didn't you want final drive ratio's? anyway I have 4:10's with 38's and a doubler behind a manual. It works, but I am going lower. When I had 35's it was perfect, but I think 5:13's are in my future
 
Yea, but since I have OD and marv doesnt, I can go with steeper gears. I can cruise at 80 mph at 2500 rpms with the 4.56s. At the same rpms with no OD and 3.73s you can only go 68 mph, or 56 mph with 4.56s. And to do 80 mph with 4.56s and no OD you will be above 3500 rpm!! Thats all I am saying. I like the low gearing of the axles because it helps alot of take off and gas milage. Then the OD does the rest. Of course I am talking about a vehicle that is driven to the trail. If its a trail only rig then doubler all the way. But the reason above is why I didnt go to a doubler.

Dan
 
C6 - 2.47:1, 203 & 205 - 2:1 each (close enuff) & 4.88s = 48:1 with 42" tires... a little lower honestly wouldn't hurt my feelings. Just a guess but 60:1 would probably be just about perfect for me from a seat of pants guestimate.

As far as that theoretical "add 2:1 for the torque converter"... it's a line of crap thought up by someone with a torque converter that got jealous of his buddies ratio with a clutch... it's meaningless garbage just fed to you to make you feel better IMHO.
 
Wow... Matt,

How do you REALLY feel about that 2:1 increase in crawl ratio from the TC...? /forums/images/icons/smile.gif

Marv
 
About the TC Multiplier...

So, who should I believe - Manufacturers of Torque Converters, an envious guy or a Ford Guy?
 
Interesting, as I am throwing out my auto (TH350/203), in favor of a stick (sm465/203/205).
I don't like the engine speed vs no power to wheels analogy of a TC (x2 theory). I have a TC withh a stall at ~ 1900. What a pain it is to throttle the pedal to get the tires to go over rocks.
Then again, I guess I will soon discover "what a pain it is to feather the clutch to get the tires to go over the rocks"
/forums/images/icons/smile.gif
 
Actually with a manual and a doubler you seldom ever touch the clutch except to shift on the flat areas. I idle up touch the brakes to settle the suspension and let it idle on up.
 
Sorry to get off subject..

But I think the real question is going to be, are you mostly freeway/mileage or will this be a dedicated trail rig?

My Blazer sees double, and triple usage. It hauls my boat, is a 2- 3 day a week daily driver and I LOVE to go rock crawling.

I travel about 20 miles each way on the freeway to work. So a little taller gears are the way to go for me. I love my 3.73s and 35" BFGs... I spin around 2500 RPM going 65. Traffic here is blistering fast 80mph is the norm. I usuall run around 3000rpm to keep up with traffic when it is not "rush hour" or slow. If I keep it around 2500 rpms or lower, I get about 14 mpg. When I go above this I get around 12 mpg.
I know 4.10s will be much better for off-hwy and towing. But really, when I travel 2 hours to get to the trail head, I can hardly wait to get the doubler and keep my 3.73s!

Of course, now I am thinking about getting some 4.10s and 38.5 (really are 37.1"). These gears and tires should get me to about 2350rpm at 65. I think this would be better for hwy use. Around town driving is probably going to suck, BUT with the sm465 low granny, I should be able to make some of it back, if I don't punch it. /forums/images/icons/smile.gif

So as always, the question is...how are YOU going to drive your rig?
 
Well if you sit down & really think about it, it's a infinintly variable slip. A number I would belive is it's effective gear ratio once your above the stall speed to calculate final drive in motion. Just taking a guess outta the air I'd think that would be about 1.1:1 or so, but I can't say for sure. But as far as overall gearing multiplication, 2:1 is just too generic, & I belive it's something someone came up with just to compare apples & oranges. If you or anyone else think you can change my mind on this, feel free to educate me though, I'm always up for learning something new.
 
When I learned to drive in the rocks with a stick we didn't use the clutch. If you had to stop you turned the engine off. When you started again you cranked the engine with the clutch out. If you had a safety switch on the clutch pedal you bypassed it so you could do this. Has this changed now? And that was before the doublers were out there. Had a flat fender with a sbc sm420 and a twin stick tc 5.38s in the axles with 33" tires.
 
this is the setup most serious trail rigs I see use. it seems really wierd to me to watch a guy stall while climbing rocks and then just fire up the rig still in gear. It seems to work well but I bet it takes some getting used too.
Justin
 
Watson uses the same 2 multiplier on his calculations. I figure he knows what he's doing.
 
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