Hi all. Brutus my 1972 F250 Camper Special has the 390/C6 in it. It's has 90,000 original miles on it. I Bought it with 60k on it in 2018.
I would like to change the gear oil in its differential.
A friend gave me 6 quarts of Mobile 1 Blue Label 75w-90 "limited slip" SYNTHETIC gear oil. Can/Should I use this in my upcoming drain and refill? I'm not experiencing any issues other than the undignosed clunk described in the next paragraphs.
How do I determine what type of differential I have? Is it limited slip or just a conventional differential?

I do hear an undetermined as to why, drive line clunk when accelerating lightly from a stop and the twing,twing,twing type noise a ujoint that is dry or failing makes.when the truck moves forward slowly and easily This twine ujoint noise was much more noticeable 6 or 7 months ago and was dramatically reduced when I greased all the ujoints.

I just bought every part number u joint and center support bearing assembly the truck might take from O'REILLY. In the next few weeks I'll remove the drive shaft to replace the ujoints and center support bearing and want to make sure I had parts available to do so. O'REILLY lets me bring back the parts that I don't need. I'll be changing the differential fluid when I drop the drive shaft
BESIDES "clocking" the driveshft is there any other tips to help me do this u joint stuff smoothly?

 

I think the gear oil will be fine for your truck. Chances are you have a conventional, open diff, not a limited slip. There's a couple things you can check. You can decode the door tag. It will have an axle code printed/stamped that will tell you what type and gear ratio is in your rear end. Failing that, if you jack up the rear of the truck with both wheels off the ground, but the drive shaft still attached and the trans in park, rotate one tire and see which direction the other tire turns. If they turn the same way, it's limited slip. If it turns opposite, it's conventional.

 

There should be a metal tag bolted to the D60 cover listing the ratio and an L if it contains a LS Traction-Lock. With only 91K miles, it probably should still be there.

 

thank you so much. for the reply
[img alt="Metal door I.D
Tag"]https://cimg9.ibsrv.net/gimg/www.ford-trucks.com-vbulletin/2000x1504/20241110_124649_5ab8704804c549c1370922854e5b7b38c0 2dfc62.jpg[/img]
Metal door I.D Tag

 

[QUOTE=52 Merc;21397785]I think the gear oil will bqe fine for your truck. Chances are you have a conventional, open diff, not a limited slip. There's a couple things you can check. You can decode the door tag. It will have an axle code printed/stamped that will tell you what type and gear ratio is in your rear end. Failing that, if you jack up the rear of the truck with both wheels off the ground, but the drive shaft still attached and the trans in park, rotate one tire and see which direction the other tire turns. If they turn the same way, it's limited slip. If it turns opposite, it's conventional.[/QqUOTE]
thank you for the heads up!

 

[QUOTE=52 Merc;21397785]I think the gear oil will bqe fine for your truck. Chances are you have a conventional, open diff, not a limited slip. There's a couple things you can check. You can decode the door tag. It will have an axle code printed/stamped that will tell you what type and gear ratio is in your rear end. Failing that, if you jack up the rear of the truck with both wheels off the ground, but the drive shaft still attached and the trans in park, rotate one tire and see which direction the other tire turns. If they turn the same way, it's limited slip. If it turns opposite, it's conventional.[/QqUOTE]
thank you for the heads up!