front vs rear gears

[davytenn]

I have '73 Bronco, want to change the gears from 3:50 to 4:11. Not sure if the front is a D30 or a D44. Can't see any identifiable markings. Rear is a 9 inch. Do the gears have to be exactly the same? Also, thought about buying one of JBG's complete 44 disc fronts, but they list 4:09? Never heard of that one. Any idea of what the transfer might be? ( stock, I'm guessing)

Thanks, to any all replies.

 

[Seabronc]

You could check the approximate front ratio by raising the wheels off the ground, engaging the hubs and then turn the wheel while counting the turns of the drive shaft. Put a mark on the drive shaft and see where it is after one turn of the front wheel. If it is 4.11 for ex. it will have turned just slightly more than 4 revolutions.

The gears need to be either matched or very closely matched. Some times you will see a match like 3.54 with 3.57 to allow the front wheels to pull slightly more than the rear for off road use. If they are not closely matched you will have a pretty nasty experience when going into 4X4. For normal ice or snow covered roads in 4X4, I wouldn't want any mismatch at all since that may lead to some skittish handling.

Don't know about that thing on JBG. Give them a call, they are pretty knowledgeable and helpful. Besides they may like to know if their web site has something that needs fixing.

Good luck,

>-

 

[STLKIKN]

Quickest way to identify the D 30 front is to look at the top of the steering knuckle....

Four small bolts is a 30, one large nut is a 44. A 30 diff cover is flat up both sides and round on the top/ bottom.

The 44 cover is more octagonal in shape. A 73 should have a 44 unless swapped put by a previous owner.

EBs have wider variations in ratios than most other trucks... The rear with 3.50 ratio will have 3.54 front.

The rear 4.10 or 4.11 will have a 4.09 front.

 

[S_bolt19]

should also be a tag on both diffs to tell you what gear ratio is in both. The other thing is that yes, you have to have the same (or close to the same within about 3%) gears or you will do serious damage to either or both axles, transfer case...could possibly get into the engine if you force the issue. If you do have different gears in the pumpkins, do not put it in 4wd or you will wish you hadn't. The absoluet best prices around for gear changes is Mike Kirkus at Complete Offroad ( http://www.completeoffroad.com ) Get in touch with him for your gears.