I bought this 95 F-450 it sat on a dealers lot for a while when I bought the truck I have driven it ever since. Gradually I'am getting more of a locker push in the steering and I'am getting some backlash in the driveline.

I don't know if its possible something has loosened up and started working again ?

Its winter time now (rain and more rain) so I don't have a chance to pull the diff cover to have a look to see if its a open diff or not. The last time I jacked the truck up which was couple months ago the I turned one wheel and the other didn't move. I left the truck in gear and the other tire turned backwards.

I really don't know what has all off a sudden caused some driveline back lash and steering push. I actually have had a little steering push but now it seems to be a litte more prominant now that I changed to LTX M/S Michelins for steer tires.

 

if one tire went backwards you have a open diff.

 

could be a tired posi maybe? or a posi in need of the Friction Modifier?

 

The truck could have a posi in it but there really isn't many limited slips made for the Dana 80s in these trucks. I don't know who the previous owner of the truck was but it must have seen allot of time in the mud it must have belonged to a farm or something. It has a tow hoop under the front bumper so it tells me this truck has been pulled quite abit.

I know the only way to tell for sure is pull the cover I didn't have time in the summer I may have to wait till a sunny day and pull the cover and change the gear oil. I do want to install a Detroit True Trac if it does have a open diff or if it does have a clutch type Limited slip I would replace it. Thats on the wish list of things to do or when ever my wallet allows

I don't think the backlash I'am feeling is in the transmission all the U joints are good. I really don't think that the Toyo M-55s on the rear have that much grip on the road they over power the steering.

 

Whats the door code say for what axle you have? THis will tell you for sure what (unless someone swapped it out, but i doubt it) you have back there, but offhand the few owners manual i've looked at, i didn't remember seeing a ls option listed for these trucks.

 

The problem is I don't know if its been changed the diff cover does have silicone gasket maker around it. The door post code is 73 which is supposed to be 5:13 gears open diff. From the rpms I get on the highway it feels like the axle gears gotta be 4:63s the rpm at 100km/h 62mph is less than it was with my 89 F-450 with 5:13 gears and 5spd.

Like I said the only way to tell is take the cover off I guess I will have to do that to know for sure. Like I said this truck was used alot offroad or I assume it was with the dried mud caked on the front axle.

 

You know immediately if you forget to add friction modifier......clack.....clack.....clack.....

 

is this an auto truck??? if so, tat owuld explain the lower rpms, the 5 speed have a .78 or .76 overdrive (i cant remeber which one). and the autos have right around .7 or .72

 

Well I had a chance to pull the diff cover off it was sunny and a good day to do it plus my curiousity got to me. The one bad part is I have a open diff I was hoping it was a limited slip but it wasn't. I confirmed my suspicion the gear ratio is taller its 4:63s which is uncommon in the diesels usually they are 5:13s it wasn't my imagination the rpms were lower. Usually you find the 4:63s in the gasser F-Superduty trucks so the previous owner swapped in the taller gears makes me a little happier.

I'am also glad I decided to check and change the gear oil man it was a awfull color it kinda looked like it was alot of rust

No chunks or missing teeth that was a good thing the cover was a SOB to get off it was well glued on with silicone. It took a long time to clean it up the back side was pretty rusty so I took a grinder with a cup wheel and cleaned it up. It took 3 litres of oil thats alot of squeezing of those bottles I used Penzoil Gear oil (80w-90).

Having a Detroit True Trac is going to be on the to do list for awhile I have to put that 1000 dollars into the dumping flatdeck. I would like to have a traction aid in the diff to combat the one wheel wonder.

 

Why would you want higher gears? You looking for better mileage?

 

I like the taller gears because it keeps the engine from screaming at highway speeds. My previous F-450 had 5:13 gears at 100km/h (62 mph) the old IDI would be revving at 2800 rpm. The truck pulled good at low rpms with the 5:13s but I had no road speed.

Another way to think of it most people complain about 4:10 gears being too low with regular 235/85R-16 rubber well my truck current truck with 4:63s worse. I wouldn't want to go to even taller gears then I would be shifting too much as the truck does weigh 8400lbs which is only 200lbs away from the gvw of a 3/4 ton HD P/U.

I'am glad that I did change the oil that stuff that come out was Yuck poor gears and bearings.

 

Have you run it since you changed the fluid? Just curious if it helped.

 

I was driving the truck today I will probably check to see if I have any leaks tommorow when it sunshines it was raining way to hard to be crawling under the truck.