Clunking Sound After Gear Swap

[Mustang Jim]

OK, so I finally did it. I finally swapped the 2.79 gears out of my 64 1/2. I picked up a complete center section, used but in good shape, with 3.40 gears about 3 years back, but I never had the time to make the swap until today. It took me alot longer to complete the swap today and I finished it in 4 1/2 hours. That was due to one of the axles being just a total bear to remove. Also, getting the center section in place was not a picnic either. Those things sure are heavy to lift when you're lying on your back. All things considered, the whole process is simple and fairly straightforward. I took it out for a test spin afterwards and it feels like a different car now. No more playing with the clutch in 1st gear and acceleration is much improved.

One problem though. When coasting in gear to a stop I hear a clunking or knocking sound coming from the rearend starting at around 20mph to about 5mph. It seems to be timed with the turn of the wheels, but I am not sure what it is. The sound is not huge and it does not cause any vibration in the vehicle. Does anyone have an idea as to what is causing this and any recommendation as to what I should look at first?

Thanks,
Jim

 

[dennis112]

OK, so I finally did it. I finally swapped the 2.79 gears out of my 64 1/2. I picked up a complete center section, used but in good shape, with 3.40 gears about 3 years back, but I never had the time to make the swap until today. It took me alot longer to complete the swap today and I finished it in 4 1/2 hours. That was due to one of the axles being just a total bear to remove. Also, getting the center section in place was not a picnic either. Those things sure are heavy to lift when you're lying on your back. All things considered, the whole process is simple and fairly straightforward. I took it out for a test spin afterwards and it feels like a different car now. No more playing with the clutch in 1st gear and acceleration is much improved.

One problem though. When coasting in gear to a stop I hear a clunking or knocking sound coming from the rearend starting at around 20mph to about 5mph. It seems to be timed with the turn of the wheels, but I am not sure what it is. The sound is not huge and it does not cause any vibration in the vehicle. Does anyone have an idea as to what is causing this and any recommendation as to what I should look at first?

Thanks,
Jim

Check your rear universal joint for looseness and ensure that the U Joint is setting properly in the yoke. Are the bolts tight?

 

[Mustang Jim]

The bolts are tight, but I did have a bit of an issue keeping the u-joint properly seated while tightening it down. I didn't get a chance to take a look at it today, but I will be working on it tomorrow. Hopefully, that's all it is.