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  • 1965 - 1973 Classic Mustangs -General/Talk-
  • Classic Mustang Specific Tech

clunk when shifting in reverse

  • Thread starter Thread starter kubesh
  • Start date Start date Apr 3, 2010
K

kubesh

New Member
Apr 3, 2010
2
0
0
Apr 3, 2010
#1
  • Apr 3, 2010
  • #1
Hi every body, new guy here, I have a 65 coupe with a c4 auto and every time I put the car in reverse I get a big clunk. is there a bushing on or around the differential? If so where? thanks
 

RGS0907

New Member
Aug 21, 2003
429
1
0
New Jersey
Apr 3, 2010
#2
  • Apr 3, 2010
  • #2
kubesh said:
Hi every body, new guy here, I have a 65 coupe with a c4 auto and every time I put the car in reverse I get a big clunk. is there a bushing on or around the differential? If so where? thanks
Click to expand...

Before you tackle anything to big, check the U-Joints (on your driveshaft) first, it's probably that.
 

rbohm

Founding Member
Apr 12, 2002
6,698
550
204
67
tucson,az
Apr 3, 2010
#3
  • Apr 3, 2010
  • #3
generally the front U-joint takes the most abuse, and thus wears out first. check it for free play, and if there is any replace it.
 
R

rsweld

Member
Dec 30, 2009
64
0
6
St. Marys, GA.
Apr 3, 2010
#4
  • Apr 3, 2010
  • #4
ditto to the 2 above.
 

dbfarr

Member
Sep 17, 2005
191
0
17
Boise ID
Apr 3, 2010
#5
  • Apr 3, 2010
  • #5
if you replace your u joints, take the drive line to a shop have it balanced and install spicers. The cheap GNB crap never lasted me more than six months, ... mmmmm busted u joints, spinning driveshaft, stranded in November.

On another note, don't let me send you astray, but when my trans clunked into reverse, I had a bad motor mount. 'Might wanna check those.
 

RGS0907

New Member
Aug 21, 2003
429
1
0
New Jersey
Apr 4, 2010
#6
  • Apr 4, 2010
  • #6
dbfarr said:
if you replace your u joints, take the drive line to a shop have it balanced and install spicers. The cheap GNB crap never lasted me more than six months, ... mmmmm busted u joints, spinning driveshaft, stranded in November.

On another note, don't let me send you astray, but when my trans clunked into reverse, I had a bad motor mount. 'Might wanna check those.
Click to expand...

+1 on the motor mount too.

What is GNB?
 

JonK

Member
Jun 6, 2007
276
0
16
Nashville (Smyrna), TN
Apr 4, 2010
#7
  • Apr 4, 2010
  • #7
I had a clunk in forward and reverse, though it was my UCA, found that my motor mount bolts (thru bolt and block bolts) could be spun by hand, engine to trans bolts were also loose, seller stated that it had a rebuild 5yrs. ago, hope they weren't loose all that time. Doesn't hurt to check all the driveline bolts and the cond. of your motor/trans mounts but I bet you'll find as mentioned above that it's ujoints.
Jon
 

Bitter

New Member
Feb 21, 2010
42
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0
Apr 5, 2010
#8
  • Apr 5, 2010
  • #8
I vote for U-joints. That's a classic symptom.
 

dbfarr

Member
Sep 17, 2005
191
0
17
Boise ID
Apr 7, 2010
#9
  • Apr 7, 2010
  • #9
GNB

Gnb is the brand for the garbage u joints that Schucks / Orielly sells. I think I've gotten them at Napa too, really lousy quality. They cut loose and cause frowns nearly every time...

I've been working on this car for nearly five years now, getting really tired of doing anything twice. In fact, I'm getting to the point where I won't even touch my wrenches unless I have quality parts!!
 

JDS68Stang

New Member
Sep 3, 2007
153
1
0
New York State
Apr 7, 2010
#10
  • Apr 7, 2010
  • #10
If the car drives fine at all speeds with no vibration etc... most likely then it is the motor mount(s) as said.

I checked my U-joints by hand on my old 68 with my brother who's also a gearhead and both seemed fine, car would start shaking in drivetrain at around 30 MPH.
I discounted $500 off when I sold it for that reason and new owner said new U-joints fixed the problem, so can't always tell by hand checking I learned that one the hard way.
 
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