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40Th Anniversary Howling At Highway Speed

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I'm asking because I said I would. . .


I've had my 40th for a couple of years now and it has always made a howling noise when I reach 60 mph+. It only happens with acceleration, sound goes away when you lift off of the gas, doesn't matter what gear. It seems that it occurs when the pinion angle is changed at that speed. Meaning, as I'm driving at 60 mph and it is howling, if I go over a bump or dip in the road it wil stop for a brief second. Based on other threads and talking to a few TS members it sounds like it is the ring/pinion. They say this typically happens if the gear wasn't set-up correctly or if it was a bad set of gears when it has been swapped, most common to 3:73.


According to SAI, they did not swap ring/pinion during conversion. My Ford tech says it does not appear thet the cover has ever been off of the housing. However, I rotated the drive shaft and the driverside rear wheel turned 3-3/4 turns and I turn around 2,000 rpm (maybe it's 2,200) in 6th gear going 65 mph. I have the same wheel/tire package from conversion.


I contacted Ford Racing to order a new ring/pinion and described the issues. They said to hold off and ask other 40th owners if they have the same issue before we go to ripping in to the differential. They thought it could be the Eibach suspension package, hard bushings, a bearing or the 2 piece drive shaft (mentioned there is a bearing in it). The stock LCA, UCA and mount are still on the car. I have not greased the suspension and not sure it has been done since conversion back in 2009 and 4,000 miles later. Only been in the rain once, never through a car wash etc. if that matters. I did purchase grease, just waiting on the salt and sand to diisappear.


Do any of you have this same issue?


What rpm are you runting at 65 mph in 6th? Assuming you still have the same set-up



Edited by Ford Fest
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Don't gave that issue, stock gears, 3:31, iirc only 2k or under in 6th. Been awhile since I have driven the car.

Thanks Sherri. I figured you've been driving it getting ready for the celebration in April. I'm trying to figure out how to post a short video from my iPhone to give a better example. Also, to show how noisy the cabin is on my car. Again, just curious if anyone has the same issues. I'd like to know the current gear ratio before I order new gears.

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If you are driving over 60 mph and push in the clutch and coast what happens? I would assume the howling goes away?

You have a short throw shifter?

I think you're on the right track, the addition of the Eibach stuff definitely introduces more noise than stock,

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I'm not going to be able to make it to the celebration. However, I am going to Shelbyfest in Hermann, MO April 25th-26th.




I haven't tried the clutch and coast, but will. I do have a short throw shifter. I'm sure the suspension is helping with the noise. I would think all of the 40th and SS cars would have the same noises since we all have the same set-up. Guess I'm the lucky one :)


I'm going to pickup an angle finder tomorrow to see where I'm at. The 40th conversion did not replace UCA or LCA. With the ride height change using the Eibach suspension, I would think the angle is going to be effected.


If the gears need to be changed I'm going to have a friend help pull the assembly and do a complete resto to get it back to the factory look (no rust).

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Quick update. . .


We dropped the rear assembly out of the car yesterday. After popping the cover and draining the gear oil, we confirmed it has 3.73 gears installed. Looking at the wear pattern, it appears this is the culprate. I need to determine exactly what parts I need to purchase from Ford Racing to rebuild it. While it's out I want to make sure we get it right. The car only has 6,000 miles, but bearings and seals might be instore. Alex's threads have inspired me to attempt to restore the rear assembly to factory condition. We'll see how that goes.


As we were disassembling the rear suspension. I could believe all of the creaks and moans it made. The car will probably feel and sound a lot better after the suspensions is cleaned and completely lubricated. I'm hoping the bushing are all still good as it appears that the suspension hasn't been greased since it was originally installed. I can see how the Eibach rear springs clunk, springs sitting on an aluminum adjustment ring doesn't seem like the best combo. You would think they could have a thin soft rubber liner between the two pieces. I may try to add the thin liner. I know Alex has installemd H &R rear springs on several 40th and SS cars. This might be the route I go as well. I'm kind of a purest and would like to keep the Eibach if possible. I'll keep you posted with my progress.


Thank you for your feedback!

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I went with Alex and the H & R springs. The coil overs put on the 40th was terrible. I picked up my car, drove over to Alex's and said fix it please. Only took a couple hours in the car to make that call. It was a horrible ride. All was well with the H & Rs till the Eibachs blew out, about 20k miles. Have FFRP shocks now.

Edited by msmap
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Alex changed my springs also. First Eibach's lasted less than 5k before leaking oil. 2nd set good for 10k so far.


My right front started leaking after the first test drive. Didn’t see it until I unloaded at home. Shelby sent out replacement parts right away.

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I wondered why Alex was changing out the springs and shocks on so many 40th and SS cars. I was under the impression Eibach was good stuff.

It's pretty good stuff, but not adjustable. You can only adjust ride height,. The Eibachs are just to stiff for most people. I just changed out my front Eibachs for adjustable Koni's. That's after almost 6 years.

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