Gearing...all years the same?

[dchawk81]

This is probably a REALLY dumb question but if I were to want 4.10s in my Navigator...or even go nuts with 4.55s...do I need the same model year pickup's rear end or would any Ford rear end give me the junk I need for the pumpkin?

Just curious if gears are gears or if there are certain types beyond the ratio itself.

For the record, I doubt I'll do anything since it already has 3.73 in it but I hear people talk about changing theirs and I'm wondering how they're sourcing them.

[Jersey_Joe]

This is probably a REALLY dumb question but if I were to want 4.10s in my Navigator...or even go nuts with 4.55s...do I need the same model year pickup's rear end or would any Ford rear end give me the junk I need for the pumpkin? Just curious if gears are gears or if there are certain types beyond the ratio itself. For the record, I doubt I'll do anything since it already has 3.73 in it but I hear people talk about changing theirs and I'm wondering how they're sourcing them.as long as it's the 9" rear you can put what ever u want in there. But. If u have the 3.73. Ur pretty much golden. That's really the best scenario IMO.

[dchawk81]

Okay thanks. I wasn't sure how that worked.

Indeed on the 3.73. It seems like the best compromise. Tow dollied an older F-150 with scrap steel beams and a junk snowplow in its bed without really feeling it so that's alright by me so far. The 4R100/5.4 helps.

[RhinoZ24]

as long as it's the 9" rear you can put what ever u want in there. But. If u have the 3.73. Ur pretty much golden. That's really the best scenario IMO.

^X2 as long as its the same size gear, you're good to go. 3.73 and such is just the teeth ration between gears. The actual size of the gear is what matter so you can be sure it fits.

Dodge Sucks, Chevy Swallows

[dchawk81]

Cool. What do you measure? Is it the pin gear length or is it the ring gear diameter?

In other words, if someone had the guts laying out on his garage floor, what would I lay the tape across to determine if he's actually selling a 9" rear end?

Further, how do I measure or check the ratio?

[Jersey_Joe]

Ok. I think it's a 12 bolt pattern and a 10 bolt pattern. 12 bolt being the HD and 10 being the 8.8

[FXd_up]

Cool. What do you measure? Is it the pin gear length or is it the ring gear diameter?

In other words, if someone had the guts laying out on his garage floor, what would I lay the tape across to determine if he's actually selling a 9" rear end?

Further, how do I measure or check the ratio?
The "size" of the diff refers to the ring gear diameter. So if someone were to have a diff carrier all taken apart in front of you, then it'd be the diameter if the big ring with teeth on it. And the ratio could be determined by counting the number of teeth on the ring gear, but that's also dependent on the diameter.

As long as you have the STOCK tire size, 3.73 is the best ratio for towing and economy. The difference between the 3.73 and 4.10 is too minimal to be a worth while upgrade IMO, unless you happen to have your diff taken apart and you happen to have a 4.10 R&P sitting around.

[dchawk81]

Gotcha. Thanks.

I'm not changing anything. Just curious about how it works since I hear/read about it so much. Definitely don't want to be the redneck who can pull stumps but maxes out at 40mph. Lol.

I do have nearly stock tires on the original wheels and the 3.73. Sized up to be wider but went shorter ratio so nearly identical diameter. I'm happy enough with it. Wouldn't mind taller for better economy actually but it's not bad for what it is and I liked how it pulled my sister's 5700lb scrap truck on the dolly. Easy peasy.

Definitely not giving up the towing for the economy. I have an Escort wagon for that. Purchase price was around the same as new gears ($250). :lol: