how different are 3:55 gears to 3:54 gears?

[comanche87]

hey everyone. i got a question. the dana 30 i have in my truck now thought to be 3:55 which came out of a part time 4x4 90 xj.i don't know what the gearing would be in that. i am going to put a 87 dana 30 axle with 3:54 gears.this axle is in much better shape. found that out when i cleaned off the tag. also out of a part time 4x4. is that going to destroy my 242 t case since i have it in full time allways? the old axle has been in the truck for a few months now. is it going to be ok since i run my truck in full time with that slight difference in the axle. my rear has dana 35 with 3:55 gears. I'm basicly broke right now and don't have any money if need to either change the rear axle or change the front gears. the truck seems ok to me but wanted to know what u guys think. thanks.

[ComancheKid45]

I'm pretty sure they are 1 in the same and thet you can run both axles in unison with no problems :thumbsup:

[freakjeep93]

it shouldnt hurt it but id ask pete or eagle first

[comanche87]

paging dr pete!!! paging dr eagle!! :dunno: :dunno:

[cracker]

Eagle or Pete are not needed.

 

I am here :D

 

They are A-Ok to run together.

 

The difference is .3% so no biggie.

 

Ever look at axles other than Dana? They use slightly different ratios as well and as long as they are SUPER close, they can be used.

 

There is some room to play with gears (but not much). For example: 4.11 gears can work with 4.07's to 4.15.

[comanche87]

ok i just wanted to make sure. i had never bothered to check that out untill i cleaned the tag off the 87 dana 30. i always thought the front axles had 3:55 in them not just 3:54. the only feeling i got from the axle thats in it now was when i was at almost to full turn and feel the wheels turning from the full time engaged. i never had looked at other axles since i was on a budget and now unmployed and getting poorer. i figured id stay with factory axles since I'm not going crazy with the truck. its my only daily driver. i have no more toys. at least for a while.

[SuperWade2]

I have a 4.10 R&P in one axle and a 4.11 in the other and everything is A-OK...

[Pete M]

The ratios of which you speak come from dividing the number of ring gear teeth by the number of pinion gear teeth. Because axles come in different sizes, there are different numbers of teeth in them. For example, the Dana 30 will have 41 teeth on the ring gear and 10 teeth on the pinion, giving a 4.10000 ratio. The Dana 44 on the other hand has 45 teeth on the ring gear and 11 teeth on the pinion, giving a ratio of 4.09090. the Ford 9": has 37 and 9, giving 4.11111 Round them off and you get 4.10 and 4.09 and 4.11.

[WBKrazy]

hmmm... i always figured that the slight difference in gears is why they tell you not to use the 4x4 on dry pavement... i had the same question a while back when i replaced the front diff in my old '91 bronco, and thats what i was told... that had 3.55's out back and 3.54's up front as well....

[Pete M]

The tires themselves are likely to be a bigger difference front to back than the gears. But the reason is still true. the front and back will likely never be exactly the same.

[comanche87]

Not sure is size will make a difference but I'm running p225/75r16 On all 4

[Pete M]

tire wear, tire inflation and initial tire diameter all play a role. :thumbsup:

[Eagle]

hmmm... i always figured that the slight difference in gears is why they tell you not to use the 4x4 on dry pavement... i had the same question a while back when i replaced the front diff in my old '91 bronco, and thats what i was told... that had 3.55's out back and 3.54's up front as well....

There will be a bigger difference the first time you go around a bend in the road. The front wheels travel farther than the rear wheels around corners. That's why you shouldn't run part-time 4WD on dry pavement.

[Pete M]