heavy duty time !!!!

[85 oil burner]

How yall doin got a ? here,I got a 85',2wd,3/4 ton,burb with a 6.2 diesel,8 lug rim,and a "SF" 14 bolt axle,and I am lookin to replace it with a 14 FF axle,I am also lookin to install a true 4.56 detroit locker in it,anybody ever do this ? I have heard a lot of 4 wheel guys doin it but rarely 2 wheel,how hard would it be and would it bolt up to my driveshaft,also would this severley affect my "MPG" or would I only lose a mile or 2,if its gonna kill my diesel then I will stick with the reg. gears but I really would like to bulletproof that rearend my rearend is givin me fits and I thought why not this would be the perfect excuse,and the thought of extra leafs and heavy gears sounds fitting for the ol' beast I have heard a lot of good things about the "FF" so any advice would be greatly appreciated thanx in advance,long live the square bodies !!!! Last of the tough trucks.

 

[bucket]

The 6.2 won't like those gears if you drive on the highway much. You can use a 4.56/detroit axle from a military truck but you have to relocate the spring perches and shock mounts. Or put C30 spring hangers and shock mounts under the truck and relocate the passenger shock mount on the axle.

 

[crazy4offroad]

4.10 is the most common ratio to come in the FF, 3.73 "sometimes". Setting up a locker in a FF is fairly easy, since there's no shims on the side bearings, just the spanner nuts. Makes setting the backlash, mesh pattern and preload a breeze! Depending on your tire size you may want 3.42 or 3.73, also depends on your transmission.

 

[85 oil burner]

foun a needle in a haystack

thanks for the info guys,much obliged.well here is a little more info I forgot to meniton,the trans is a 700 r4 and I am currently running 3.73 gears and gettin about 20 to 23 mpg depending on how nice I am to the ol' throttle,well hte truck gods must ahve smiled on me I found a "FF" axle out of a 95' gmc 3500 and the guy put a 3.42 ratio in it instead of the 4.10 to pull 5th wheels,so I think I might go with that,also the yard is selling the whole assembly springs and all so I think I am just gonna go ahead and do that to avoid all the conversions too.
thanx for the advice and keep on truckin.

 

[crazy4offroad]

With the 700R4 the 4.10s would have been a better match.

 

[85 oil burner]

switchin up.

well I havent installed everythimg yet I have just been junkyard doggin nothin solid,so 4.10 hmmmm ,that doessound like more up my alley as long as I dont lose my mpg I mean it is 2wd,so I get a little better mpg anyway but yeah,the 4.10 sounds more like what I need I plan on towin my buddies trailer for huntin' season and I do a lot of highway but I dont slam on the pedal just 70 to 75 mainly heck the thing can barely go 100 goin downhill on a good day so yup sounds lioke a 4.10 in the rear thanx again for the info.

 

[crazy4offroad]

If you tow much with the 700R4 be sure to not run it in overdrive. Just shift it to "3" and boogie, it will make the trans last longer.

 

[85 oil burner]

yeah thats what I have been hearin my buddy has a burb and almost blew the 700 r4 on his 95' with a 350 while he was towin his camper up huntin,heavy ol bugger too but he was haulin in 4th gear all the way it didnt give him problems for a while after that but in the summer it was clear that his tranny didnt like that towin and it started actin up,man I am sure glad you reminded me to to do that or I might have been stuck in northern mi, with no burb in the woods in nov. I aint no city slicker but it would be a loooong huntin season havin no burb to tow that trailer so many thanx. thats why I was originaly thinkin about throwin a 4.56 on it and callin it good so I wouldnt have to stress out the tranny but I aint got the deep pockets to fill the 41 gal. fuel tank every time i pass a station and with diesel up to $4.30 a gal. in some spots the 4.10 seems a whole lot nicer on the wallet so I am much obliged for all the info.