Classic Mustangs List Archive

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Mail From: wal (Wal Marshall)


My 69 Cobra Jet has developed a noticeable "bump" in the transmission on
moving off. It seems to be coming from under the centre of the car but its
hard to be sure.

It sounded like a the C6 was moving on its mountings. I checked all the
mounting bolts and they seem tight. Also checked the driveshaft universal
bolts and they are OK as well. So I removed the Transmission cross member
and mount to investigate further. The rubber mount looks fine but the holes
that mount the cross member to the car chassis seem to be elongated, and Im
thinking that this the possible movement under takeoff load. Im guessing
that the cross member may have been loose for some time and the holes are
now flogged oval.

Solution seems to be to weld up and redrill the cross member mounting holes.
The chassis mounting holes may need work as well. Im guessing that the side
of the cross member with two holes for a through bolt has accurately drilled
holes, where as the other side with a single mounting hole is meant to be
slotted to allow for mounting differences from car to car?

Has anyone else on the list had this problem?

May you all have a wonderful Xmas.

Wal Marshall

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Mail From: dano (Dan O'Reilly)

Sounds very much like a worn u-joint to me...have you checked yours?

At 03:29 PM 12/21/2008, Wal Marshall wrote:

>My 69 Cobra Jet has developed a noticeable "bump" in the transmission on
>moving off. It seems to be coming from under the centre of the car but its
>hard to be sure.
>
>It sounded like a the C6 was moving on its mountings. I checked all the
>mounting bolts and they seem tight. Also checked the driveshaft universal
>bolts and they are OK as well. So I removed the Transmission cross member
>and mount to investigate further. The rubber mount looks fine but the holes
>that mount the cross member to the car chassis seem to be elongated, and Im
>thinking that this the possible movement under takeoff load. Im guessing
>that the cross member may have been loose for some time and the holes are
>now flogged oval.
>
>Solution seems to be to weld up and redrill the cross member mounting holes.
>The chassis mounting holes may need work as well. Im guessing that the side
>of the cross member with two holes for a through bolt has accurately drilled
>holes, where as the other side with a single mounting hole is meant to be
>slotted to allow for mounting differences from car to car?
>
>Has anyone else on the list had this problem?
>
>May you all have a wonderful Xmas.
>
>Wal Marshall

---

Dan O'Reilly
1971 Bright Red Mach 1
2002 Black Deluxe Convertible
Colorado Springs, CO

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Mail From: wal (Wal Marshall)


Sounds very much like a worn u-joint to me...have you checked yours?

Thanks Dan.. I checked them both about 6 months ago, and replaced the rear
one. I didnt think to recheck the front one, so will do that.

Cheers, Wal

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Mail From: dano (Dan O'Reilly)

Check the rear on again, too. I had my driveshaft worked on by a really
good driveline shop that I trust, and one thing they mentioned is that they
see lots of failures (relatively speaking) of cheap u-joints. I don't know
what you bought when you replaced it, but if it was lowest-cost instead of
good quality, well, ...

Also, have you checked play in your rear end (the car's, not ...)? If seen
excessive play cause that sort of issue as well.

Good luck!

At 03:40 PM 12/21/2008, Wal Marshall wrote:
>
>Sounds very much like a worn u-joint to me...have you checked yours?
>
>Thanks Dan.. I checked them both about 6 months ago, and replaced the rear
>one. I didnt think to recheck the front one, so will do that.
>
>Cheers, Wal
>
>_______________________________________________
>Classic-mustangs mailing list
>Classic-mustangs at lists.twistedpair.ca
>lists.twistedpair.ca/mailman/listinfo.cgi/classic-mustangs
>
>Visit the Classic Mustang Wiki! sauce.donair.org/~cm/

---

Dan O'Reilly
1971 Bright Red Mach 1
2002 Black Deluxe Convertible
Colorado Springs, CO

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Mail From: walt (Walt Boeninger)



Wal Marshall wrote:
> My 69 Cobra Jet has developed a noticeable "bump" in the transmission on
> moving off. It seems to be coming from under the centre of the car but its
> hard to be sure.
>
> It sounded like a the C6 was moving on its mountings. I checked all the
> mounting bolts and they seem tight. Also checked the driveshaft universal
> bolts and they are OK as well. So I removed the Transmission cross member
> and mount to investigate further. The rubber mount looks fine but the holes
> that mount the cross member to the car chassis seem to be elongated, and Im
> thinking that this the possible movement under takeoff load. Im guessing
> that the cross member may have been loose for some time and the holes are
> now flogged oval.

I assume this ovaling is side to side.....

Unless I am mistaken, one side is oval to allow for a bit
of slop during assembly ... my 67 TA car has bit more than
stock sized ovaling.... and an extra hole.... I don't think
this is your problem....

You say the rubber "looks" fine ... have you really tried
prying it from the crossmember? I broke on of these on
my 72 C6 and the tranny really bumped the car... it
"looked" OK at first....


--

Regards
--------------
Walt Boeninger
walt at boeninger.net
webmaster at norcal-saac.org
shelbytransam.com

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Mail From: W427 (David)

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