best gear for a DD with 31" or 33"?

[jkufen]

I have an 86 B2 4x4 and by the end of the summer I am wanting to put a larger set of tires on it probably 31" or 33" depending on what kinda of deals I can find and was considering changing the gears. I want a set of gears where I can keep decent gas mileage because its my DD. I was thinking about gears out of a mustang or f150. I know nothing about gears and I don't claim to be any kind of mechanic so I am hoping you guys can help. I am not going to be doing any serious offroading or nothing. Thanks!

 

[4.0B2]

I dd mine w/ a 4.0/auto/4.56's/33's.. i wouldn't want anything less.

you have the 2.9 correct? for power sake i'd say 4.56's on 31's and maybe even 4.88's for 33's. some people might say 4.10's for 31's... idk, i like my 4.56's for 33's even on a DD. with my 4.0 i'm getting about 17 in town and 19-21 on interstate (depending on where i set the cruise)

if you're curious to know what your RPMs will be with either set of gears/tire combo, go here.. figure out how to use it.

http://www.grimmjeeper.com/gears.html

pick your transmission, t/case(bw1350 is what you have...same gears as 1354 i believe so you can just use the 54), under drive will be "none", hit calculate(or whatever it is), scroll to the BOTTOM 2 charts and look at different speeds at the different RPMs, you can even change your RPMs for the chart. the bottom chart is MPHs showing you the RPMs. either way.

 

[jkufen]

That's exactly what I need to know. I do have the 2.9 now but I am thinking about doing a 4.0 conversion. Right now my 60 mph is about 2000 rpms which is 22 mpg for me. I was wanting to stay in the high 17's 18's but I understand you cant have your cake and eat it too, cant have big tires and good gas mileage but i would like to keep the mileage reasonable. Now with the new gears is there anything else I need to change with them? I will most likely pay someone to do it I just don't want to get tricked into buying all this unnecessary stuff. Thanks for the help!

 

[kunar]

i have 31's and 4.10's with a 4.0 and IMO they are just a little deep. before i did the swap though, i ran a 2.9 and i liked it. your best bang for your buck by far is going to be getting an entire rear axle and front 3rd member with 4.10 gears already in it. ford put 4.10's in trucks in the 80's, look for automatics. manual trucks didnt have that option. around here you can get an entire axle for $100 to $150

 

[4.0B2]

rear axle would be easy to find 4.10's. from a 95+ explorer 8.8 with disc brakes.
then find a d35 ttb (you won't likely find a 4.10 ttb axle) and just regear it. that way you can have the stronger axles and only regear once. there is a little fab work in the axle swaps tho.

 

[4.0B2]

if you have new gears installed, it'd be gears, install kit, new fluid, and labor.

but i wouldn't spend money on those stock axles if you plan to wheel it decently hard. the 7.5 and d28 are the weaker axles. 8.8 and d35 would be what you want.

 

[kunar]

rear axle would be easy to find 4.10's. from a 95+ explorer 8.8 with disc brakes.
then find a d35 ttb (you won't likely find a 4.10 ttb axle) and just regear it. that way you can have the stronger axles and only regear once. there is a little fab work in the axle swaps tho.

yeah, the explorer rear came with 4.10's and is reasonably easy to find. as for the ttb, if he could find a 4.10 3rd for a d28, it would be a pretty simple swap. he says he doesnt wheel it much and mine has held up fine for driving in the snow and such. they aren't all that rare, like i said though you have to look at automatics for a donor truck. not at all trying to contradict you, just giving him options.

 

[integman]

i need help with this too. soon i will be getting a dana 44 and a 9in. i think im going to get 37in tires but dont know what gears to use.

 

[4.0B2]

i need help with this too. soon i will be getting a dana 44 and a 9in. i think im going to get 37in tires but dont know what gears to use.

5.13's IMO

 

[4.0B2]

yeah, the explorer rear came with 4.10's and is reasonably easy to find. as for the ttb, if he could find a 4.10 3rd for a d28, it would be a pretty simple swap. he says he doesnt wheel it much and mine has held up fine for driving in the snow and such. they aren't all that rare, like i said though you have to look at automatics for a donor truck. not at all trying to contradict you, just giving him options.

actually, if you read what i wrote, stating ttb axle 4.10 w/ d35 right before my ()---- they are rare. trust me, I looked. the only ones I found were some that had been regeared and for sale on here. 4.10 d28, i have no clue, i never looked for that.

regardless, if he does 33's; i'd want 4.56's at least. 31's i could see 4.10's.