Do all full-sized Broncos have a limited slip in the front differential? Mine is a 1990 with an "19" on the sticker. Does this mean open diffs front and back or just back? Thanks for any help.

 

you have open diff's 3.55 front and rear (at least that's what it left the factory with) Now if it said "H92", then you would have LSD front and rear ("H" being the LSD indicator code for a rear LSD and "2" being the code for front LSD)

 

Actually, the front is almost always 0.01 numerically lower than the rear - the front ratio is 3.54:1 for that code.

 

>Actually, the front is almost always 0.01 numerically lower
>than the rear - the front ratio is 3.54:1 for that code.

I'll second that!

 

How often are you suppose to service the oil in the front diff? My '90 EB bronco has ~195k miles and I never had it changed yet.

Is that a disaster?
A friendly tire shop person said that if I don't drive it in 4x4 mode, it doesn't put any wear or load on the front diff. so don't worry about the oil change. Is there any truth to that?

When I do the oil change, I was told to get a suction pump and pull the old oil out, otherwise it will take too long for the thick oil to merely pour out. Anybody with expertise on this?

What is the best and longest lasting lube that won't affect seals?

Also, what is the reason for the 0.01 difference in the front to rear axle ratio?
What happens if they are both exactly the same ratio?
Doesn't the slight differences in tire diameters make for other inaccuracies that need to be compensated for?

Ron

 

Hi, one reason to change the front diff lube is it is open to air through the vent tube. The other is that all hydrocarbon compounds change, and you do not want a glob in there if you ever need to go into 4wheel drive. Go to Autozone or similar parts store, buy a $5 suction gun.
Thorougly clean the area around the filler plug. Real clean, you don't want any dirt to get in. Remove the plug. Remove the old lube. Then cover the ground with lots of paper towels, and cut the tops off the bottles of new lube and start squirting. You will have a little mess.
It may cost $10 to do the job, but it is better then having a multiple $$$ repair.
Bruce

 

[updated:LAST EDITED ON 24-Dec-02 AT 00:30 AM (EST)]I didn't change the oil in mine for over 250Kmi and when I recently had it rebuilt, it looked pristine. Even the mechanic was surprised by how clean the oil was, and I did some NASTY off-roading and HEAVY work with my truck. There is no service interval on the front diff oil because it'll last longer than the axle.

If you're worried, just pull the plug & dip your finger in the oil, which should be RIGHT at the bottom of the fill plug hole. It'll stink from the Sulfur, but if it looks like honey, it's fine.

If you do decide to change it, pumping it out is the only way, unless you want to disassemble the whole front axle - the axleshafts keep the diff from coming out of the axle assembly, so you have to start by removing the L hub from the spindle. If you split the diff off the axle without pulling the shaft, you can't clean it enough to get a seal back.

The slightly higher ratio in the front makes the front wheels steer better off-road.

 

How well does the pump method work in removing all the oil? I want to put synthetic in and don't want a mix. A mix of dyno oil and synthetic oil can jell--not good!

 

In a D44IFS, I wouldn't expect more than 5oz to remain if you spent some time working on it, but it all depends on how low you can get the end of the pickup tube, the temperature of the oil, and how long you let it trickle down the insides of the diff.