I have an '83 bronco with an 8.8 rear, and i have an '81 part bronco with a 9" rear, does the 8.8 have anything over a 9"? Also, the '81s gvwr is 5350, and the '83 is 6000, how come? I was going to put the '81s 4speed into the '83, i can't tell what kind of 4-speed it is, where can i look up the codes on it to see what it is, and the codes on the rear ends to find their ratios, etc.

 

In your case other than brake sensor which I dont know if the 93 used . The 9" will bolt in if gears r same . The 9" will take about anything you can dish out.The 87 up trucks have a speed sensor mounted to top housing , And the 90 ish and up actually get speed reading from it. . Good luck

 

he said 83 not 93 so he should be okay.

the ratio should be listest on the little metal tag on the diff cover bolt. you can also look it up by your ID sticker on the drivers door jamb.

As far as the tranny you need to get some casting numbers or numbers off an id tag on it.

NP-435 gear ratios
1st - 6.69
2nd - 3.34
3rd - 1.79
4th - 1.00

T-18 Gear Ratios
1st - 6.32
2nd - 3.09
3rd - 1.69
4th - 1.00
R - 7.44

t19 has the same except 1st is 5.11 and 1st and reverse are syncronized, they are not on the t18 or np435. The np top cover is aluminum. the t18 and t19 is cast iron just like the case. 6bolts hold it on. 8 bolt on the np435. the np has a pto cover on the right(pass) side. i think the t18 and t19 have one on both sides but i dont remember.

 

The 8.8 and the 9" are both fairly well accepted as being quite durable. The 8.8 was fitted with a port for the VSS on models after 1990 if I am recalling correctly. The 9" axle housing is one entirely welded piece whereas the 8.8 has a cast differential housing with an inspection cover and the axle tubes are press-fit into the diff housing. Some would argue durability in favor of the 9" for this reason but you would really have to be getting into some serious trouble to mangle either assembly.

 

The downfall of the 8.8 is the wheel bearings riding on the axle. if your bearings go, they eat your axle. Also, if your axle breaks in neer the diff, your wheel and axle can depart the truck. On the 9", the wheel bearing is riding on an inner race. So the bearing can get pretty bad without hurting the axle. Because the bearing is held at the wheel, if the axle breaks inboard, the wheel stays on. The other advantages are its very eazy to change gears on the 9". That's why the drag racers use them. Also, there are many after market upgrades for 9" because of the drag racers. They can be built to accept up to 900 hp. In our case, if you upgrade to full float axles on the 8.8, you will have a better unit than the 9". But if you are going stock, put the 9" in. (especaly if you run big rubber)

 

WHERE DO YOU LOOK-UP CODES for trans and rearends? Why is weight different on 83 than 81?

 

The diff ratio is usally on a tab on one of the cover bolts. If yours is gone or unreadable, you an jack up the truck and turn the wheels (both the same) one full turn and count the driveshaft rev's.

The trans code should be on the sticker in the door. There are many things that make up the weight class. Could be trans mission, brakes, diff gears or just springs