03/04 Cobra rear end in my '93 Mustang. This thing has been HOWLING something fierce recently so I have pulled it to try and see what’s going on. It sounds similar to what an improperly set up gear install sounds like. Admittedly, I’m pretty inexperienced with what to look for in diagnosing the root of my problem, and I plan to take this to someone who has the tools and know-how to properly set these things up. I just want to know as much as I can before doing so.
Clunk, clunk, clunk…normal?
I’m definitely not a professional, but that definitely sounds wrong.
Watching a pretty informative video right now going over the set up of rear ends. I’m pretty sure what I’m dealing with is an improper backlash, especially since the problem gets worth with speed. When I got this rear end the pinion flange had to be swapped as it came from a Cobra, my wonder is that the crush bearing wasn’t replaced and when the pinion nut was re-torqued it screwed the backlash…and a few thousand miles later is when the symptoms became most evident??
Who setup the gears?
As far as I know the factory did. Ford 3.55’s
Factory my ass… You can see that te gears are set incorrectly in your video alone. Those gears are definitely not set up right.
They will clunk a little when dry when checking the back lash but something sounds really wrong with that. Almost like somethings hitting. The back lash should be .006 to.010 if you can check it.
Dropped the whole thing off to Dave at Competition Trans, diagnosis is a lot of messed up shit in there. Backlash checked in at .020, hence the loud clunk. Pinion bearing was shot. Spiders gears all chipped up, If I understood him correctly in our brief phone call, the spider gears had more or less welded themselves together in certain parts. He agreed that a pinion flange swap without a new crush bearing installed most likely was the beginning to the end of it all.
Brand new diff is going in, along with the obvious (bearings, seals, shims, etc.) He’s pretty confident the ring and pinion are still ok enough to get back to a good wear pattern. I really don’t know much history, nor does it really matter…I’m just looking forward to driving the car without that a ticking time bomb out back.
Yikes!
Yeah, nothing about that sounded good at all. Let me know if you feel like recommending Competition Transmission. I have a Z32 tranny that’s going to need re-assembly. Thanks and good luck.
Update: Dave at Competition Trans is the man. After speaking with him in person at length, someone had definitely been in there before…there were non-factory stampings in there that I learned were the ‘signature’ of a mechanic. Anyway, pretty much everything was trashed, so I opted out for a fresh set of gears as the existing ones he set up and couldn’t get a good seat pattern out of them. Have put about 500 miles of driving on and can’t hear anything out of the rear anymore. Amsoil 75w/140 gear oil and friction modifier keeping it all cool in there.
Glad to hear that worked out :tup:
They rebuilt the diff on my Expedition and it came out perfect. They were recommended by Rod over at Mr Bestwrench on Grand Island who I used to autocross with and fully trust his opinion.
:tup:
Thanks for the review and follow up. I will be needing some rear diff work in the next few weeks and am looking for a reputable shop to set everything up for me.
If you don’t mind me asking what did you pay to have the rear set up? Obviously I assume this wasn’t a standard rate job since there was disassembly and diagnosis involved.
Sexy :tup:
Think it came out to ~$840 total. Wanna say $275 labor, and it was a standard rate job as far as I understood it, with a flat fee for ring and pinion set up ($200). I was hit for an additional $75 when he swapped in the new set of gears. I probably could have disputed this as he originally thought he would be able to get them set, but upon install found them to be not 100%. I wanted 100% so I went with the new gears, which were $150 through him. Everything in there is factory Ford, no Chinese shit. Also, add ~$40 for the gear oil…so total job was just under $900.