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  • 1965 - 1973 Classic Mustangs -General/Talk-
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Clunking Sound After Gear Swap

  • Thread starter Thread starter Mustang Jim
  • Start date Start date Nov 10, 2006

Mustang Jim

Founding Member
Nov 1, 2001
373
3
18
New Jersey
Nov 10, 2006
#1
  • Nov 10, 2006
  • #1
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

15 Year Member
May 15, 2005
1,561
36
79
Amish Wonderland of Central PA.
Nov 10, 2006
#2
  • Nov 10, 2006
  • #2
Mustang Jim said:
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
Click to expand...

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

Founding Member
Nov 1, 2001
373
3
18
New Jersey
Nov 11, 2006
#3
  • Nov 11, 2006
  • #3
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.
 
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