Im at the cross roads

[oktogo]

Ok let me tell you what im working with i have a 89 bronco with a 351 and a c6 i have 6 in bds suspension liftt and 3in body with 38 in ssr radials i have stock gears that are 3.55 my rear diff had a l/s but i dont hink it works any more i would like to get better gas millage whould new gears help me with that?

i dont do much off roadin but when i do its muddin or drivin off the road thru a field or at a friends house i have some money to change my gears but i dont know if my axils will handle my tires,and if i change the gears which size 4.11 488? will im there should i put limitedd slip front and rear i can come up with the money over the summer if i have to

plz leave me your comments i would realy be greatful also i live in the south and other than the mud whe have no hills or rocks so my axils are mostly on level ground i may be able to come up witha d60 but is 8 lug and my rims are 15in so that wont work

 

[Broncobill78]

Did you or someone else swap in the C6 ? The 89's came with an AOD and that overdrive gear makes a big difference in your mileage. The clutches in the trac-lok may well be toast but it would probably be worth adding a bottle of friction modifier to see if that helps (the L/S diffs need to have it added periodically or the clutch pack goes away). With 38's you'd want at *least* 4.56's but 4.88's would be a better choice. If you have the $$$ to add a trac-lok up front (a spool will be cheaper but you have to make some compromises with those) then it's a good idea for off-roading but if you honestly spend most of your time on the pavement then you'll have to decide if you really want to spend the cash on something you'll rarely use (on the other hand if you're regearing the axle anyways it's only a few hundred bucks more to change the differential)

Swapping in the D60 will mean that you'll have to change rims as well and unless you want to run 5-lugs up front & 8-lugs out back you'll have to swap in D50 knuckles to get the 8-lug pattern all around (and while you're at it you could also use the D50 shafts).

38's are really too heavy for the stock axle shafts & U-joints. Unless/until you upgrade I'd anticipate breakage. If you're set on keeping them and don't want to break parts then you need to consider either the D60 swap or upgrading to hardened moly axle shafts. You don't have many options with the D44 other than to upgrade to the stock D50 shafts or commit to a D60 there as well.

 

[oktogo]

it does have a c6 which gear will get me better gas millage 4.56 or 4.88 will the d50 ifs axil shafts be a good fit or will i have to make some adjustments?

 

[Broncobill78]

The 4.88's will bring you closest to what the original final drive ratio was & that in turn will put the engine pretty much back into it's powerband. However you sometimes run into problem physically fitting the larger gearsets into the axle. If they don't fit you'll need new carriers.

Since you DO have the C6 another option you can consider is a lower planetary gearset for the transmission. Most of the ones I've seen offer about a 10% reduction in 1st and 5% in 2nd. You'll have to run the numbers yourself (by that I mean actually doing the math on what the various options will net you for a final ratio AND the accounting end of how much each option will cost) but it may end up you want to install 4.56's and the planetary set as opposed to just the 4.88's or the 4.88's & the tranny gears to get the greatest possible improvement in mileage. Here's a link to one set, other companies like TCI also offer them but when I just ck'd TCI wanted $600+ for theirs while Oregon Performance has them on sale for $205 (regular price $216) so you can see it's always worth shopping around for the best price.

http://www.oregonperformancetransmission.c...NTP-KC6GRP.html

As far as the D50 shafts go I honestly can't tell you from personal experience because I've never actually swapped in a set. I have several sets of factory manuals and from what I can tell the D50 measurements are the same it's just an up-gunned D44 that gets used in the F250. From what I can see the D50 parts are direct replacements. This would be even more true if you swapped both the shafts AND the spindles/knuckles in order to get the D50 8-lug rotors. Maybe someone else here has actually done this and can shed some light on it. Anyone.......anyone.........Bueller ?

 

[oktogo]

i odnt know but the gears in the tranny may have been changed because it was completly rebulit with a level 10 kit not by me the previous owner and will 4.56 gears fit with no problem? i realy dont need any more power i have great pick up and can easly spin the tires at the start i just could not stand the mpg my rpm at 55 is about 2100 to 2200 is that good or should it be higher

 

[oktogo]

Bump