4.88 in front/4.86 in rear OK?????

[desertspeed]

I am in the process of swapping a 9" into my 2001 F150 4WD. What I have discovered is that new gears for my front diff (8.8" reverse cut) are only available in 4.88, and 9" gears are only available in 4.86.

Is this close enough to be OK, or will it cause binding issues? Does anyone have any fisthand knowledge with this?

Thanks!!

[Pete_Rose]

Is the truck full time 4 wheel drive? If yes, then its not ok, you will build up a small (very small) amount of bind in the drive line. If no, then you are ok because the small amount of bind will translate to slipage in the dirt.

[desertspeed]

Is the truck full time 4 wheel drive? If yes, then its not ok, you will build up a small (very small) amount of bind in the drive line. If no, then you are ok because the small amount of bind will translate to slipage in the dirt.

No, it is not full time 4WD- thanks for the info.

[Pharaoh XJ]

even if its a part time I think its ok specially in the sand

[85yota]

you can have like a 1% difference and be fine.

[SimonSays]

i have a dana44 front and 9in rear.. its the same thing... 4.86 for the 9in 4.89 for the dana 44... works fine.. i run the truck in 4 high all the time and never had an issue... as long as its within 1-2% u should be good....

[desertspeed]

Awesome- thanks for all the replies.

[bajafx4]

I've run a truck with a 4.10/4.11 combo on the street (when 4WD required) and never had any issues. There's probably a larger difference in final drive ratio between front and rear just because of different tire wear rates.

[loufish]

Actually running a little front gear biased works good for off road...

4:10 frt/4:11 rear is ideal, the front end turns a little faster then the rear causing the front to want to pull out of sand & mud rather then just plowing in...The bias is small enough not wreak havic on the driveline...as long as you keep off the pavement...

[summerinmaine]

This may be a foolish question, but how do you calculate a ratio so close, but not exact?

I'm in the process of re-gearing my Jeep, and for the D44 the ring is 41 and pinion is 10, so it's a 4.10 (though some call it a 4.09 and some a 4.11). If you're dealing with ring teeth divided by pinion teeth, how do you get ratios that differ by such a slight amount? Why the difference? :confused:

Does the diameter of the ring/pinion gear come into play here?

[jesusgatos]

41 divided by 10 equals 4.10

[summerinmaine]

41 divided by 10 equals 4.10


My point exactly. So how do you get a ratio of 4.09, or 4.11?

More to the point, how does the OP get 4.88 for one axle, and 4.86 for the other? Certainly not by a ring/pinion tooth comparison without something else figuring in.

[summerinmaine]

I've run a truck with a 4.10/4.11 combo on the street (when 4WD required) and never had any issues. There's probably a larger difference in final drive ratio between front and rear just because of different tire wear rates.


This point makes sense to me. You'd get a difference of 1-2% based on different tire wear rates or tire pressures (i.e. rolling circumference), but how do you get it with ring/pinion teeth comparisons?

[jesusgatos]

My point exactly. So how do you get a ratio of 4.09, or 4.11?

More to the point, how does the OP get 4.88 for one axle, and 4.86 for the other? Certainly not by a ring/pinion tooth comparison without something else figuring in.
Dunno, but 45 divided by 11 = 4.09. My guess is that those two different axles each has a different number of teeth on the pinion. That would account for the small difference.

[Haycock]

i have always been told that if your within .09 you will be ok for off road. i know tons of people running 5.38 in the front and 5.29 in the rear with no problems. i wouldnt worry at all on or off road if your within .02.

[summerinmaine]

This may be a foolish question, but how do you calculate a ratio so close, but not exact?

I'm in the process of re-gearing my Jeep, and for the D44 the ring is 41 and pinion is 10, so it's a 4.10 (though some call it a 4.09 and some a 4.11). If you're dealing with ring teeth divided by pinion teeth, how do you get ratios that differ by such a slight amount? Why the difference? :confused:

Does the diameter of the ring/pinion gear come into play here?


BTW since I posted this comment, I've run some numbers and educated myself.

It turns out that with widely different ring/pinion combos, you can get ratios that differ by only 0.01. Who knew? :D

Bottom line? I still agree that differences of 1-3% are probably within the range of normal F/R tire wear, and are probably not significant from a lock-up/driveline wear standpoint.