help! need info. of rearend oil level

Jeff Bratton

Registered User
Wanting to know if there is an approiate (sp?)level on the oil the rearend? The seal where the halfshaft goes into is leaking a little on the pass. side. I have bought a new one, so fixing it will be soon.

Aiming to replace it ASAP, but until then was going to add oil. Is there such a thing as over filling? This is why I throwing this question out to you guys.

Anyone?

Thanks!

Jeff B.
 
hmmmmmmm..

Well, you can't really overfill the rear-end. I beleive it must come up to the hole where your filling it at which is the small bolt you take out. Obviously you can't bring it past the hole because it will leak out lol. I read it in the Chiltons manual I beleieve.
 
If you fill the differential with only the rear wheels up on ramps, then you will overfill it. I don't know how critical this is, but to be on the safe side, I left the plug off, slowly drove down the ramps, then very gently reversed up them again, and then closed the plug.
Remember that when you do a complete change of differential fluid, you need to add 4oz of friction modifier - about $5 from Ford.
 
Jeff - yours looks like an '89-91 (with those side marker lights), so check to see if it has a limited slip diff. before adding the friction mod. Diff capacity is 3.25 pints (or 3 pints + 4 ozs of mod) of 75w90. If you don't take the back plate off to fully drain it, you'll need one of those suction pumps to extract the old fluid & it's also worth buying one of the little plastic install pumps (PepBoys has them) for pumping the fluid back in (pump screws into the oil bottle); because there isn't much room to get a quart bottle above the diff height for gravity flow. As mentioned, just fill until it stats to overflow, then lower the car with the plug out (put a pan or newspaper underneath) let the excess drain off, then reinstall the plug. You can usually sqeeze back underneath to install the plug without raising the car again (unless yours is lowered, of course).
 
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