Hello.
I have a 1984 F-250 with a 6.9. Everything is stock and when I go down the highway I think I'm turning too many RPM's at 75mph. Someone told me I had to change my rear end gear because back in 1984 the highway speeds were 55mph and vehicles were geared lower.
Can I just find a rear axle out of a early 2000 F250 and swap? Or do I have to take apart my rear end and buy a new gear thing?

Thank you for reading.

 

That "someone" doesn't know what they are talking about.You are approaching this the wrong way. What is the actual engine RPM at that speed? What is the final drive ratio? You can determine that from the tag on the differential. Is the transmission or clutch slipping making the engine run faster? You have to determine all this before blindly changing out a differential.

 

Another one time post and run.

 

It is frustrating isn't it!!!

 

Sometimes it is a good thing that they aren't all perfect like us, huh?

 

From the "more perfect" angle, which clearly doesn't include me, lol ..............

https://www.fordforum.com/forum/new-...posters-43284/

 

Bummer, I'm new here, was really hoping the original poster would answer you because I wanted to learn more about all of this gear ratio speak! Thanks for your efforts moderators!!!