Just recently I traveled to Missouri (12 hour ride) to pickup a new trailer I bought. I took my truck after I checking, changing fluids and etc. Well the trip went fine and I hauled back my new trailer no problem. I noticed that my rear bumper and my spare had fluid on them. After further inspection I could see where the fluid escaped from the bottom of my rearend. I shouldn't leak like that should I? Somone told me that on a long trip like that with the truck getting hot the fluid gets thin and might leak out of the seal but I shouldn't worry. I'm not seeing and kind of leak since I got back. Never had a problem with my rear and I'm up to 99K. I'm going to drain the remaining fluid out and add new tomorrow to make sure everything is ok. Never done this before but it shouldn't be too hard. Anyone have a write up or could you provide me with some simple instructions. Hoping there is a drain plug on it. Oh and I have a 1999 F350 DRW 4.30 limited slip axle. Do I need 80/90 fluid?

 

If I was going to do that I would get a Magtech diff cover and install that. It holds more fluid and is vented to help with the heat. I would also put some Amsoil syn HD long life 80w-140 gear lube and slip lock if you have the limited slip diff.

 

Do you have a link of where I can find one. Also, how can I tell what rearend I have?

 

http://www.dieselmanor.com/gauges/gauge_kits_psd.asp

 

When I had my rear diff oil changed, the guy showed me a small metal tab on the rear diff melon that is stamped with what weight of oil to use. Also,your owner's manual should have the info.

As for difficulty: it's not difficult, but the hardest part for the guy at the shop that did mine was putting the new gear oil in! It was cold, and the stuff came out like molasses out of the Royal Purple bottles. So, if you can find a way to warm up the bottles before you try to squeeze the new oil in, that'd help. Maybe close them under the hood after you get home from a drive and let them warm up while you unbolt the rear diff cover??? Or, set them on the front floorboard inside the truck and turn the "floor heat" dial to full heat for a half hour or so??? Also, crawl up under the rear end of the truck before and see how much clearance you have at the fill valve. Even with my truck on a lift, the guy at the tranny shop was at a funky angle to get the bottles of new gear oil angled high enough to get it all out of the bottle and into the melon. So, you may do yourself a favor by doing this in advance BEFOREHAND, in case there isn't enough room if you're doing it on the ground or if you don't have a high enough jack to get room to fill it back up.

DO NOT overfill the rear diff. Put in the required amount. Use a full-synthetic gear oil of the proper, recommended viscosity, making SURE that the gear oil you use has a friction modifier in it. Some brands don't have it, so you must get the friction additive and add it to the new gear oil. Some brands (like Royal Purple) already have the friction additive in it.

Last thing: double-check with your local Ford stealership and see if there is a gasket? or sealant? of some kind between the melon and the diff cover that will need to be replaced??? I have an '02 with the 3.73 LS rear. I've pulled a 3000lb trailer a few times and I've never had any rear gear oil "come out because the oil gets hot". That's a new one to me; I thought the rear diff melon is a closed, sealed unit. You might want to check that out further, too....

Good luck with it. Should't be too difficult of a project. Make sure you've got all the right tools and sockets, oil, gaskets/sealants FIRST. And please, please, please... put safety first!

Best,
DS

 

Thanks for your insight DS. I noticed this afternoon that the fluid that did leak, came from where the driveshaft connects to the rear. Maybe my problem is
a little more advanced

 

Sounds like the pinion oil seal. Unless you have the proper tools and are familiar with what has to be done, you might be better off letting a professional do the job.

 

think it needs immediate attention? It's not leaking now while I have been driving it but I'm sure it will happen again during a long trip.

 

Check the vent tube on the top of the differential and see if it is open. Unless its leaking alot of fluid, I would try changing the fluid with synthetic (75w-140) and adding the proper additive.