i got my new (used) rearend home today according to the door sticker on the donor truck it is a axle code 86(3.73).. now i didnt see a tag on the cover plate so im still assuming its a 3.73 gear..i thought i would remove the brake drums and turn the axle and count the number of turns the of the pinoin gear but the pinion never turned..is this a bad sign? so i turned the pinion gear and the axles would turn but i could only turn the pinion gear about 3.5 or so turns and it wouldnt turn no more at all..is this a bad sign? i think i heard one time i could turn the axle 1 turn and the pinon gear would turn 3.73 turns to give me a 3.73 gear ratio. does this sound right..im trying to confirm the gear ratio and to make sure its a good rearend before i put it under my truck...could some of the experts help me figure how to tell if its a good rearend and if it is a 3.73...thanks

 

Just pull the diff cover off.

99.9% of gears will be stamped with the ratio on the ring gear so you can see it with the cover off.Then you can look inside to see if anything is broken or not.

 

i took the cover off and i didnt see anything broke but i did see some rust on the ring gear..not to bad but there where some rust in spots...does that hurt any thing...i did see the numbers stamped on the ring gear but im going to drain it and clean it up so i can see whats on it.. im concerned now about when i turn the axels the pinion doesnt turn..if i turn the axels real fast the pinion will turn some but not alot

 

If it is an open that's not an issue...the spider gears in the carrier are turning, but not the turning the pinion. It is a problem if you can spin both sides at the same time and the pinion does not turn. You are witnessing the shortcomings of an open diff offroad, one wheel can spin independant of the other.

Take that rust off and clean the inside real good, but surface rust will not harm the R&P.

 

thats what i was thinking but if he turns the pinion one of the axle shafts should move.

 

Yup, even easier way to test it.

 

ok thanks carl just wanted to make sure i was right i will be sending you money here really soon

 

well i guess i got screwed on this rearend...i thought a 3.73 gear ratio had a ring gear with 73 teeth but the ring gear in this rear end has 41 teeth...the number on the ring gear are E37W AB 1141 ... it has ford stamped on it so im guessing someone pull the 3.73 out of it and put this in it..my luck i guess

 

You need to divide the ring teeth by the pinion teeth to get the ratio.

 

i figured it out ..11 teeth on pinion gear and 41 teeth on ring gear = 3.73...lol..i love learning...thanks guys

 

i would like to flush it out so what could i pour in to flush the dirt out that wont hurt anything

 

Couple cans of brake clean or carb cleaner work great.

 

cool...thanks