Slant Six Forum :: Rear End Vibration

Quote:

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

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.

read again Dan, "from rear axle".
yes other "clunks" from other areas,
but the driveline will not carry those to the rearend.
Some are 'normal' from the rear axle, but should not
be easy to hear from standing outside the car.

Quote:

I belive, could be wrong, that new spiders are not made
for the 7.25 axles

Yeah, they are. P/N 5017203AA, unrealistically expensive from the dealer, almost certainly available from all the normal sources of rear axle parts.

Good to know there out there and thanks for a part number!!

Quote:

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

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.

Author:	Art Gladfelter [ Tue May 22, 2007 8:30 am ]
Post subject:	Rear End Vibration
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.

Author:	SlantSixDan [ Tue May 22, 2007 8:41 am ]
Post subject:
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.

Author:	Art Gladfelter [ Tue May 22, 2007 8:28 pm ]
Post subject:
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.

Author:	SlantSixDan [ Tue May 22, 2007 8:34 pm ]
Post subject:
Quote: Rear springs were revised/replaced at 220K miles....42K ago. OK...and when did this rear-end vibration first show up?

Author:	Art Gladfelter [ Tue May 22, 2007 9:44 pm ]
Post subject:
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.

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Author:	Eric W [ Wed May 23, 2007 12:48 am ]
Post subject:
Have you checked the transmission mount?

Author:	emsvitil [ Wed May 23, 2007 1:03 am ]
Post subject:
It was balanced, but did you replace the U-joints?

Author:	Mister Twister [ Wed May 23, 2007 5:04 am ]
Post subject:
Quote: 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. Almost sounds like tire balancing, We agree poss trans mount or tail shaft bushing in trans. Hope this helps Don

Author:	Art Gladfelter [ Wed May 23, 2007 8:50 am ]
Post subject:
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.

Author:	SlantSixDan [ Wed May 23, 2007 8:58 am ]
Post subject:
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.

Author:	Ron Parker [ Wed May 23, 2007 7:51 pm ]
Post subject:
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

Author:	Jeffc [ Fri May 25, 2007 4:21 pm ]
Post subject:
"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....

Author:	SlantSixDan [ Fri May 25, 2007 4:29 pm ]
Post subject:
Quote: "clunk" sound from the rear axle 'in a change of direction' is spider gears.... if U joints are good. 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. Quote: I belive, could be wrong, that new spiders are not made for the 7.25 axles Yeah, they are. P/N 5017203AA, unrealistically expensive from the dealer, almost certainly available from all the normal sources of rear axle parts. Quote: 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 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.

Author:	Jeffc [ Fri May 25, 2007 4:58 pm ]
Post subject:
Quote: Quote: "clunk" sound from the rear axle 'in a change of direction' is spider gears.... if U joints are good. 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. read again Dan, "from rear axle". yes other "clunks" from other areas, but the driveline will not carry those to the rearend. Some are 'normal' from the rear axle, but should not be easy to hear from standing outside the car. Quote: I belive, could be wrong, that new spiders are not made for the 7.25 axles Yeah, they are. P/N 5017203AA, unrealistically expensive from the dealer, almost certainly available from all the normal sources of rear axle parts. Good to know there out there and thanks for a part number!! Quote: 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 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. 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

Author:	Art Gladfelter [ Wed May 23, 2007 8:03 pm ]
Post subject:
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.

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