Correct ddifferential oil??

[19thunderbird66]

Just did a rear end replacement on a '66,can any one tell the correct weightofdifferential oil on this model?? Please help a new member get this 'ol bird flying again!! Thanx,bob

[YellowRose]

Correct differential oil??

Bob, there are several posts regarding this I found during a Search on "differential oil". Several were by Alexander. However, they pertained to Squarebirds. As I recall, he used 80/90W oil in his differential. I do not know if it is different for a Flairbird though. If you have a shop manual, you should be able to check what is required under Lubricants. You might do some searching under 1966 differential oil also. I did not search with that criteria.

[RustyNCa]

Bob, there are several posts regarding this I found during a Search on "differential oil". Several were by Alexander. However, they pertained to Squarebirds. As I recall, he used 80/90W oil in his differential. I do not know if it is different for a Flairbird though. If you have a shop manual, you should be able to check what is required under Lubricants. You might do some searching under 1966 differential oil also. I did not search with that criteria.

Yes, that is what we just refilled my son's 65 with.

[YellowRose]

Correct differential oil??

Thanks, Bryan! I was hoping a Flairbird owner would come a long and tell us what they using in their Flairbirds. I figured it was the same thing that us Squarebird users do, but was not sure. Here is a thread about this. Alexander talks about this a bit and also which oil to use. Red Lion and Lucas brands are mentioned also. Thanks for the input, Bryan?

http://www.squarebirds.org/vbulletin/showthread.php?t=1276&highlight=differential

[RustyNCa]

Thanks, Bryan! I was hoping a Flairbird owner would come a long and tell us what they using in their Flairbirds. I figured it was the same thing that us Squarebird users do, but was not sure. Here is a thread about this. Alexander talks about this a bit and also which oil to use. Red Lion and Lucas brands are mentioned also. Thanks for the input, Bryan?

http://www.squarebirds.org/vbulletin...t=differential

I ran the Mobile One synthetic gear oil, over the years I have really good results with Mobile One.

The oil is actually a 75/90 http://mobil.pl/USA-English/Lubes/PD..._LS_75W-90.asp

Red Line Oil I have stayed away from because friends of mine that build and run their motors hard in racing tell me to stay away from it.....

[scumdog]

My '66 has a factory limited-slip centre and I used a proprietry oil designed for Ford lsd rear-ends.

[simplyconnected]

Yeah, that's common with most limited slips now, Tom.

My Mustang 8.8 needs it to smooth out the clutches. 90W is the diff (dope) of choice, with limited slip additive to be changed ~ every 50k miles.

This little bottle goes for US$4.50. - Dave

[19thunderbird66]

Re: Rear end oil

Thanx,Ray,all my shop man. gave was "Rotunda "and the FoMoCo number back then.I do think its the lighter weight oil,tho.bob

[19thunderbird66]

thanx a lot for th reply,everybody sez use the 85-90 wt.so i guess i will,bob

[simplyconnected]

Got any idea why rear ends need such heavy oil?
Depending on the load, they get hot. Sometimes, real hot. (Especially if you pull a trailer.) Next time you go on a long trip reach under and feel the housing. That 90W gear lube quickly turns into 70W (or thinner). With all those bearings and gears transferring hundreds of HP, heavy gear lube is needed.

I commend all you guys who change your rear-end lube. If you get a chance, look at the oil when it comes out... you can see little flecks of metal floating around like glitter.

Most cars go to the bone yard with their original gear lube.

[19thunderbird66]

90W/140 rear -end oil.

thanx,I filled it wi heavy weight diff. oil and it's very guiet,bj