Greetings Folks,

Have 68 Slant Six with 262K miles with bad rearend vibration at 50-60MPH. Drive shaft was balanced. New rear wheel bearings & new tires.

Local High School Tech Shop will try to pin point exact problem.
Live in center of Pennsylvania.
Advance Auto & Auto Zone have limited parts.

Where is one of the best places to get parts????

Thanks.

Art G.

Welcome to the board.

At 262k miles, probably the rear springs are thoroughly sagged out, which can cause cause an improper rear axle pinion angle, setting up a "thrummmm" type vibration at speed bad enough to make you sick to your stomach if you look in the rearview mirror for too long at a time. New springs can be had reliably from ESPO (you'll have to call them, for there are so many rear spring variants available that they don't list them on their website).

But don't overlook the simple stuff...improper wheel/tire balance could be at work. My truck, for example, rolls smoothly only when the wheels and tires are balanced on the vehicle.

Advance and Auto Zone do indeed have limited parts. They're OK for consumables (spark plugs, oil, brake pads, etc.) but the "working parts" they offer are utter junk (rebuilt starters, alternators, carburetors, brake master cylinders, etc.) NAPA is somewhat better, RockAuto's good, and for stuff you can't seem to find, post on here for help.

You'll probably want to get the three books described in this thread.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thanks Slant Six Dan for your reply.

Rear springs were revised/replaced at 220K miles....42K ago.

Looked up rockauto and they do have many of the parts.

Thanks again.

Art G.

OK...and when did this rear-end vibration first show up?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

It has been getting progressively worse for about the last 10K miles..i.e. from about 252K to present 262K. Vibration frequency is felt in driver's seat and is about once every 1 to 2 seconds at say 55 MPH.

Have you checked the transmission mount?

It was balanced, but did you replace the U-joints?

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Almost sounds like tire balancing, We agree poss trans mount or tail shaft bushing in trans. Hope this helps Don

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'72 Duster /6 with turbo build up
'03 Ram 2500 4x4 w/HEMI 5sp 4:10 posi
My Twister Page

Thanks Don...

Rear Tranny Mount has been changed & there are 4 new tires.

Vibration is ONLY under "load" (not float) at like 45 MPH plus.

Am about to pull cover & take a look inside rearend.

Appreciate everyone's help.

Art G.

Re "every 1 to 2 seconds": Does this mean the vibration is cyclical ("Whummm....whummm....whummmm...whummm...") rather than constant ("Whummmmmmmmmmmmmmmmmmmmmmmmm...")?

If so, still sounds like a pinion angle issue to me.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

What about the unerivsal joints. Put thr car in nutral and unload the drive shaft ie no preasure on it. If you can feel any free play at either end you have a unversial problem. This is fast and doint cost nothing to check. Thanks Ron Parker









Jaggers Fabrication Slanted Attitude Dart

Greetings Slant Six Dan,

Vibration is cyclic...But we did have a bit of a breakthru this afternoon with the help of a neighbor. Jacked up & spun rear wheels w/engine.

Determined left rear brake adjusting cable had slack in it & adjuster paw was hanging loose. Corrected brake problem and this cleared up some of the "rumble" in the short 7 miles test drive we took. Need to run on expressway to see how much this really helped.

When back in driveway, neighbor had me put foot on brake, shift from forward to reverse, rev to fwd, etc....while he listened to "clunk" and watched the "play" in back U joints & shaft at front of rearend. Seems it always did have a "clunk".

Tomorrow we will try to determine if it is in U joint or pumpkin.

Thanks for all your help.

Art G.

"clunk" sound from the rear axle 'in a change of direction' is
spider gears.... if U joints are good.

I belive, could be wrong, that new spiders are not made
for the 7.25 axles, used carrier with good
spiders is the only option (other than a axle up grade or
change out).

Found out the other day that there are 2 types of
rear axles housings in the 7.25 as far as pinons go,
3.23
down all swap,
anything over 3.23 will swap,
but not--- 2.76 or 2.94 to a 3.23 or lower gear housing....

Never knew that before...... least I couldn't make them work....

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http://imageevent.com/jeffc
62 D100 225 3sp lwb
64 D100 A318 727pb custom lwb
66 D100 A318 4sp lwb
68 D100 B383 727 swb
65 Belveder A318 727 4d
65 Dart GT LA273 2bbl 904
73 Scamp 225 2bbl 4spOD
Old iron or no iron

Not necessarily. Some "clunk" sounds are normal transmission-shifting noises, and there's actually a fair amount of "clunk" acceptable from the components aft of the transmission before it becomes problematic.
Yeah, they are. P/N 5017203AA, unrealistically expensive from the dealer, almost certainly available from all the normal sources of rear axle parts.
FPC shows only one housing for all ratios 2.76 and numerically higher. The ultra-tall ratios (2.45, 2.26) have their own housing.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I tried 2 axles that had higher
gears sets removed (2.94 and 2.76
I removed them, 2.94 frist, 2.76 second,
so I know what came out)
with my 3.23s gear set, neather one
worked with my 3.23 set, neather would lash were they should.

One was a 67 housing, other was a 69.
My housing (stock) was a 73 (lost the carrier adjuster on
one side and very 'clunky' spiders (not shimed like early axles)).
The 68 housing (3rd axle housing) with 3.23 worked
and the housing number 3 was installed......

Ended up using one of the other carriers with good spiders
with my gear set, which was just fine......
glade a 'friend' gave me those axles and I didn't have to
pay for them.......

Untill this week I really had not much 'doings' with the
7.25 axles.... still learing.....
Will take a 8.75 any day over one

_________________
http://imageevent.com/jeffc
62 D100 225 3sp lwb
64 D100 A318 727pb custom lwb
66 D100 A318 4sp lwb
68 D100 B383 727 swb
65 Belveder A318 727 4d
65 Dart GT LA273 2bbl 904
73 Scamp 225 2bbl 4spOD
Old iron or no iron