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Rear end howling – rebuild, re-clutch, and caused by wrong gear oil?

November 17, 2015, 04:05:41 AM

I've had my '87 5.0 for roughly 10 years, ~224K on it, and the track-lok. Within the last few months there's been a howling coming from the rear end at highway speeds. I first assumed it was a wheel bearing, took it to a shop and explained it was only audible at highway speeds (there's always been some noise at city speeds), watched him take it just around the block before saying it needs a new rear end. He gave me the number of a guy who could rebuild it for $600 to $700.

I got a second opinion from a shop that claimed to put it on a lift, get it going, and said the differential was screaming. A rebuild was estimated at $1200.

When I bought it, the limited-slip seemed to do its job. Within the last 5 years, not so much. About a year ago I had Jiffy Lube replace the oil in it, which did nothing to help. But I've read some things that say LSDs need different types of oil than open diffs. Is it possible they used the wrong oil, and that is to blame? I don't have anything that states what type of oil is recommended, but the Jiffy Lube service receipt says they used GL5 8090 Pennzoil Limited.

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Rear end howling – rebuild, re-clutch, and caused by wrong gear oil?

Reply #1 – November 17, 2015, 11:01:48 AM

My guess is the clutches are shot in the trac-lok and you have metal on metal in there.  Get on some Mustang sites and see how easy it is to rebuild it.  I would highly recommend that you completely rebuild the rear end with that many miles on it.  You can get a complete rebuild kit and have a shop provide the labor.  The labor will be a lot cheaper if you pull the rear end and just bring them that and the rebuild kit.  Some shops will not do it if they do not provide the parts so you may want to see if the guy willing to do it for $600-$700 would come down on his price if you brought the parts and the rear end out of the car.

I had a guy at a tech school set my new gears up and rebuild the trac-lok for $200.  I brought him the rear end and all the parts.  Been in the Coupe for over 10 years and still good to go.

http://www.summitracing.com/parts/rat-3008k

http://www.summitracing.com/parts/fms-m-4700-c

I would suggest you replace the gears as well but that is up to you.  With over 200K on them I would say it is time but that is just me.

Darren

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Rear end howling – rebuild, re-clutch, and caused by wrong gear oil?

Reply #2 – November 17, 2015, 12:30:19 PM

I just had an 8.8" rear built for my Thunderbird (replaced the 7.5" rear that finally gave up). I brought the parts (FRPP full rebuild kit, FRPP 3.73 gears, FRPP 31 spline Traction-Lok with carbon fiber clutches, and 31 spline Moser axles) to a local shop that just does driveline work (rear ends and drive shafts only). The shop charged about $250 to put it together. It was all labor. They would charge the same if the rear was in the car as it's the same amount of work either way. The parts cost me about $750 so a $900-$1000 estimate for parts and labor is about right. That is if the shop is replacing everything (gears, bearings, axles, carrier).

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