Rear differential clunk

Topic: Rear differential clunk (Read 2768 times) previous topic - next topic

Rear differential clunk

December 03, 2004, 07:26:58 PM

Just pulled the driveshaft to change ujoints and the clunk I have when letting off the gas is in the differential. The ujoints are fine. How hard is it to rebuild the differential?

Re: Rear differential clunk

Reply #1 – December 03, 2004, 08:38:19 PM

I would say its perfectly normal, if you check coolcats eric has it listed as a normal phenomenon for these cars. My car had 29,000 miles when i picked it up last year and it had a major clunk. I think it was something with the design.

Re: Rear differential clunk

Reply #2 – December 03, 2004, 08:59:00 PM

chances are it is normal. My car did it since pretty much new as well as several crown vics I had either owned or driven when new or near new

Re: Rear differential clunk

Reply #3 – December 03, 2004, 09:30:47 PM

something called thrust shims would need to be added/replaced in order to get rid of "some" of the clunk. In addition,, wear on the spider gears are such as where the large pin wears an oval hole out inside these gears.

other than that,, clunk heard while giving and letting off the gas was defined to me by a fomoco mech a few years ago,,, he said..
"welcome to the world of fords"

if you get rid of this clunk,, please post as to what you did cause there are a lot of us who would like to be gone with all that so called normal rear end slop.

thrust shims would be nice to install but i checked last year with the dealer and they could no longer get them.,,, aftermarket may have them.

Re: Rear differential clunk

Reply #4 – December 03, 2004, 09:37:54 PM

Thanks for the replies! The clunk seems to be getting worse and I would like to at least reduce the jolt. I will look into it and post if any progress is made.

Re: Rear differential clunk

Reply #5 – December 03, 2004, 10:19:37 PM

The clunk can have its positive sides, for instance I can annoy my friends extremely easily. VROOOM **clunk** VROOOM **clunk** about that point the usually just look at me like wtf are you doing. I get a good laugh out of it.

Re: Rear differential clunk

Reply #6 – December 04, 2004, 12:48:13 AM

I found something unexpected when I replaced my stock Ford T-Loc with an Eaton E-Locker this past year. The shims on either side of the differential carrier are one piece (for each side of the carrier) ground at the factory based on some statisics as to how the carrier tolerances are running at a particular time (best I can determine). The problem I found was that the material they make the shim pieces out of is some sort of cheap soft metal that is susceptible to permanent deformation by the shock forces normally applied by a good running motor with a nice snappy throttle response. What does this mean in reality? Well, my shims were worn more on one side of the carrier and they were worn such that they were NO LONGER parallel to the carrier (diagonal wear). This was due to the way the force during acceleration is applied to the carrier and then to the housing through the shims. It was obvious to me after taking the unit apart that the shim material from Ford was TOO SOFT and this clearly allowed EXCESSIVE SLOP in the differential carrier. I wont go so far as to say that this is why many of these units clunk, but I will say that what I saw was a CLEAR DESIGN FLAW and lead to a ton of play in my differential. I ground the stock Ford shims down and added the HARDENED STEEL shims that come with any differential rebuilding kit between the now thinner original Ford shim and carrier so that a nice hard piece of TRUE SHIM STOCK was seeing the shock forces from the carrier! I was SHOCKED at the 0.030" lash I was seeing when measuring gear lash, and was almost as stunned to find out that just reinstalling shims to the original thickness as installed by Ford removed all of the excessive lash and put the gearset back into spec without ANY OTHER ADJUSTMENTS!!!

Perhaps I stumbled across the reason for the clunking of the Ford rearends? Let me state this clearly - the difference in thickness from one side of the factory Ford shim to the other (only 110,000 miles) was 0.010"!!!!!!!!!!!!!!!!! For those of you familiar with these sorts of things, that a HUGH amount of distortion in what should be a hardened and stable shim.

Re: Rear differential clunk

Reply #7 – December 04, 2004, 08:23:12 AM

Thanks for the details! That is some good information. Sounds like I need to print this out a find a good axle shop to take a look at it. It doesn't sound like something I could do without special tools, etc.

Thanks again for the information.

Re: Rear differential clunk

Reply #8 – December 04, 2004, 01:15:07 PM

yeah, rear ends are complicated if you know the sciences. Folks who mess with them all the time do not use the terms "setting up my rear differential" lightly. its a tuning process that has specs and all the wing dings that i know nothing about.

anyone know anything of the 3.08 rear end slop source?,,not hijacking anyones thread here,, just seems to be a good topic to open up to interested crowds.

Re: Rear differential clunk

Reply #9 – December 06, 2004, 10:38:30 PM

Quote from: jcassity

yeah, rear ends are complicated if you know the sciences. Folks who mess with them all the time do not use the terms "setting up my rear differential" lightly. its a tuning process that has specs and all the wing dings that i know nothing about.

anyone know anything of the 3.08 rear end slop source?,,not hijacking anyones thread here,, just seems to be a good topic to open up to interested crowds.

Hmmm, what I said was essentially the same thing you said above - the "thrust shims" for the differential are the same as the differential carrier shims I was talking about. There are also pinion shims, but I didn't touch those as the pinion (part that attaches to driveshaft) felt pretty tight. I suppose the spider gears/shaft could be worn too. It's easy to check - put car in neutral and rotate driveshaft back and forth - the amount of play should be fairly small (be ed if I can remember how much is too much :) ). Rebuilding does require some special tools and knowledge of how to use them though - oh, well.