This week we thought we would explain to you a thought process on an unusual issue we were asked to look at. The problem was on a ’66 Coupe that we had in for a few upgrades to be done at the same time. The seat base was made 2″ lower, the car was lowered, LED lights fitted and the problem itself was a vibration speed related which was mentioned to us. The best bit this week is that we also get to show some pictures of Yogi at work, just for his Fan Club!

We started inside where the seat base was lowered to give that all important head room in these fairly low roof line cars. There are no pics of the seat adjustment as it’s a bit of a secret how we do it, and still manages to retain that stock look.

We were told that the rear brake for the hand brake or ’emergency brake’ wasn’t working properly. We removed the wheels and drums to see what was going on in the drum setup. We have arrowed the broken self adjusting cable which caused the issues. The cable was replaced and the springs refitted. While we were into the drum we checked through the whole thing to make sure all was working.

We checked the other side which was fine with no signs of damage and working as expected. We adjusted the brake shoes on both sides ready for the road test a little bit later.

Our very own lowering block kit was fitted, link here which the customer had asked for. We took the car for a road test to make sure that everything was good with the lowering and handling as we expect. The seat base being lower down does make the cars more pleasurable to drive.

All was good with the car with regards to the upgrades we had done and the brakes were working properly and just as we expected. However the vibration was not quite what we expected, it certainly had a different feel to it. Our first thought was prop shaft.

We had the car up on the ramp and had a look over for any play. There was play in the UJ at the diff end of the prop shaft. Adam just pulled an old prop from stock that we know was fine to see if that cured it. The swap out was done and road tested.

Nothing had changed. The original prop was swapped back and the UJ changed as it needed it.

We knew the tyres were fine as we supplied and had them balanced. The half shafts were pulled out and we checked the bearings.

One side was bad the other looked to be a recent replacement and felt fine. Here Yogi checked the bearing and we filmed just how bad it was, sound as well as the movement. (Turn the volume on to hear an bearing about to implode.)

Yogi carefully cut the old bearing off and checked the shaft for wear or damage. A steady hand and finesse is required if you are going to cut these bearings off, you only need to go almost through the bearing and a tap the bearing with the hammer which will break it away from the shaft. One slip and you damage the shafts. We certainly don’t recommend doing this at home.

We got a new bearing and took it along with the shaft to our bearing press.

Here in this video below you can see the bearing being pressed onto the shaft.

Another inspection after the bearing was pressed into place was to make sure it sits correctly and feels right. We could also see that the wheel studs were odd too. Three on one side that were 1/8″ longer than the other two, they were replaced to be a matching set. Believe it or not, the slight difference in weight could make a difference for balance.

The shafts were then fitted back into the axle.

The new wheels fitted back onto the car.

With the car up in the air we ran the car in gear to see if we could feel the vibration, frustratingly it was still there. The car engine was run out of gear and it certainly wasn’t the engine balance. As the time ticked on to signal the end of the day, a cup of tea was to be had before going home with Adam, Yogi and Stu to have a chat about was was going on, and the next steps for tomorrow.

Back the next day and the plan was to swap the shafts out to see if they were slightly out of true. That made no difference, the replacement shafts of ours made no difference, again ruling out the shafts themselves. The only other thing was the differential itself. Adam got a replacement diff for Yogi and was fitted into the axle. A static run with the car in the air was done with the original shafts now back in place. The gentle test run looked promising without the vibration we had seen before, time for a proper road test.

The road test had now proved that it was the differential itself. All the original parts were back on the car except for our own diff which was now in place. We need to speak to the owner to see what he wants to do about it going forward now that we have found the problem.

Sometimes you just have to go through the parts one by one until you get to the actual cause of the problem. All the little things we found on the way to the actual answer of the problem won’t help, a process of elimination can sometimes be the only way to cure and troubleshoot these sort of problems.


Not only do we cater for the great American muscle cars, we are now starting to hold Mach-E parts and service parts as well. Ford refer to the Mach-E as a ‘Mustang’, much to some people’s dismay, but a Mustang it is. Click here to go to the page for a list of the parts we currently stock.

We mentioned last week that we are now selling more of our own branded products. We have now started to apply our own branding for those parts to make it easier for our customers to know that nobody else makes these parts.

Keep an eye on the ‘Mustang Maniac Products‘ page as it’s getting added to on a weekly basis.

Stay Safe & Take Care!

About Mustang Maniac

A business dedicated to restoration of Classic Mustangs. We supply parts for all ages of Mustangs 1964 to present day, servicing, restoration and custom builds. Anything your Mustang needs, we can help.
This entry was posted in Customers' Cars, Mustang, Mustang Mach-E, Mustang Maniac, Parts, Repairs, Video, Webshop, YouTube and tagged , , , , , , . Bookmark the permalink.

1 Response to Troubleshooting

  1. Simon says:

    Yogi is looking really smart these days well done!!!!

    Liked by 1 person

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