Gear ratio mis match

[iamsparticus]

Alright so i have a question for those of you that have run not the exact same gear ratio front and rear. I know of a few people that have done this but my question is how far off can you be example: You have 4.30:1 in the front and 4.37:1 in the rear or in the case of my buddy he has 5.12's currently in his tracker and the closest toyota ratio i can find is 5.29s we plan on a SAS soon with a toyota axle. Im thinking thats way too off from each other but i could be wrong. Looking for peoples insight on this, how far apart can you be and what have people done in what vehicles

 

[Rot Box]

There's a max percentage that is recommended, but I can't remember what it is hopefully someone else does..

I have 5.38's and 5.29's and its okay, but I would not want to run have any bigger of a gap :-\ On dirt its just fine, but on slickrock it will bind up pretty good. I went with a twin stick for the 2lo option to take some stress off off everything when 4wd isn't needed.

 

[1995zj]

The article in a past 4-wheel mag said for a DD that sees mostly pavement, you can have a 1% variance. If it's a trailer queen type rig that really only sees dirt then you'd be fine with a 2% variance.

I personally have 5.38's front and 5.33's rear. Never seen any issues.

 

[Gravy]

General consensus is 2% (in ratio) is ok.
The real test is taking the difference between (# of tire rotations x circumference of tire) between the front and rear axle.

A good example is the 76 F150. Stock it has approx 30" tires with 3.55 gears up front (d44) and 3.50 gears rear (9").
Radius=(1/2x30)
2pi x R=Diameter
D=94.25"
RC1=D/3.55= 26.54" (of travel per rotation of the driveshaft)
RC2=Dx3.5= 26.93"
RC2-RC1= .39"
% difference= 1.5%

Now try it with a 37" tire
D= 116.238"
RC1= 32.74"
RC2= 33.21
RCD= .47"
1.5% difference

Because this difference (in distance) increases with tire size, we can infer that: as we increase tire size, the amount of "bind" in the system increases if we have non matched gear ratios.

(It's interesting to note that the % difference does not change).

How much bind is acceptable?
It depends on the coeffecient of friction of the tire (Grippy vs. Smooth) and (like Rot Box said) the surface (loose vs. solid).

Your buddy would be better off running a waggy 44 with 5.13's

 

[Spork]

Meh just run a 31" on the higher gear ratio and a 32" tire on the lower.

 

[Devel]

or you can go with toyotas front and rear, be a much stronger option for chris's tracker

 

[iamsparticus]

Cool well that confirms what i was think and very good info guys. Yeah joel we plan on a toyota axles front and rear if chris can find a good deal, it maybe the only option it sounds like

 

[Chevycrew]

I agree, pushing it a little far on that one. Waggy 44 up front is my vote and leave the rear alone.

 

[iamsparticus]

the stock axles are weak sauce and he already has 33's and plans on 35's so i dont think leaving the stock rear would be wise, and a waggy 44 is the wrong side drop axle those are pass drop he needs driver drop

 

[Toad]

I ran 3.73 and 3.55 in my old ford. It was almost impossible to get it out of four wheel drive.

 

[Chevycrew]

80s waggy is drivers drop, 70s waggys is passenger drop. For the price of a driver drop toy axle he can do 1 tons.

 

[iamsparticus]

sorry i got it reversed he needs a pass drop which is what a toy axle is and the waggy i was thinking of was a driver drop. I didnt know 70's waggys were pas drop. Anyway id rather do a toy axle, cheaper and lighter

 

[rockreligious]

60's done.

 

[iamsparticus]

60's done.

60's on a tracker the axles would weigh more than the vehicle

 

[STAG]

The biggest difference I've had in the past is 3.51 front, 3.55 rear and it worked okay.