Differential/Transmission Clunk and Noises
02-13-2013, 09:35 PM
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Differential/Transmission Clunk and Noises
I am new to this site but hopefully I can find an answer soon. I bought an 85 f150 from a guy on craigslist in october. It is pretty beat up when it comes to the body like rust and stuff but the frame is solid and the engine runs strong. Recently, the real differential has been making metal on metal sort of grinding and clunking noises when driving. Especially on shifting from drive to reverse it clunks and makes a metal ding noise. I can't seem to find a pattern and sometimes it makes the noise when cruising or coasting. I will accelerate and it will make the noise too. I have taken a look at the gear oil level and it was low but I bought some oil and filled it up and no luck. Can it be u joint or other connections or is this something bad with the gears inside. I cant really take off the cover because Im afraid of not being able to put it back on. Also the bolts are on the front side near the driveshaft and will take a lot of work to just take it off. I am suspecting bad bearings or something specific like a pinion bearing or something like that. Anyone else have a problem like this? Hopefully I can get an answer.
02-14-2013, 12:49 PM
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I'm new here my self. I'm here because I have found a ton of help here many times. Anyway...... The clunk is a combination of the entire drivetrain changing directions. But it shouldn't be excessive. You said the bolts hold are in the front, so it sounds like you have a 9". If you are absolutely sure your rear diff is on its way out because of all the noise, then I would consider these options. AND THIS IS WHY LOVE FORD 9"s!!!
--First pull an axle from one side and see how many splines it has. This requires you to dissemble the brakes on that side then remove the four bolts that hold a small square plate to the backing plate. Then slide the axle out. ( I'm sure your truck has a 35 spline based on year, but you want to be 100% sure what you have). Then slide the axle back in and resemble the brakes so you can drive your truck. Then go to a junk yard and find a match. The piece you need is called a third member. It has the gears installed in it so you can take it from one axle to another without disturbing the gears. To remove it just slide both axles out of the housing then remove the nuts around the third member and pull it out. It's heavy so be careful. There is usually a tag on one of studs that tells you the ratio. Then you have two options-- A- install and use it in your truck as is if it looks good and the ratio is what you want OR B- take it to get rebuilt to the ratio you want and add a posi if you want. Option A is probably $100 start to finish. Option B would be about $400-850 depending on what parts you get and if you do it your self.
What ever you decide to do, you can drive your truck until you have all the pieces to fix it. Then just slide each axle out of your housing, pull the third member, install the new one, slide your axles back in (might be a good idea to have new bearings and seals on the axles while they are out- less than $100), put your brakes back to get her and your good to go.
--First pull an axle from one side and see how many splines it has. This requires you to dissemble the brakes on that side then remove the four bolts that hold a small square plate to the backing plate. Then slide the axle out. ( I'm sure your truck has a 35 spline based on year, but you want to be 100% sure what you have). Then slide the axle back in and resemble the brakes so you can drive your truck. Then go to a junk yard and find a match. The piece you need is called a third member. It has the gears installed in it so you can take it from one axle to another without disturbing the gears. To remove it just slide both axles out of the housing then remove the nuts around the third member and pull it out. It's heavy so be careful. There is usually a tag on one of studs that tells you the ratio. Then you have two options-- A- install and use it in your truck as is if it looks good and the ratio is what you want OR B- take it to get rebuilt to the ratio you want and add a posi if you want. Option A is probably $100 start to finish. Option B would be about $400-850 depending on what parts you get and if you do it your self.
What ever you decide to do, you can drive your truck until you have all the pieces to fix it. Then just slide each axle out of your housing, pull the third member, install the new one, slide your axles back in (might be a good idea to have new bearings and seals on the axles while they are out- less than $100), put your brakes back to get her and your good to go.
