Rear Differential - Pinion Gear?

[gonzo]

PO history and evidence suggests my particular AH BJ-7 had a difficult life. Here's a summary on the undercarrage: Front engine and trans mounts sheared/broken; rear shock mounts completely separated from frame, broken rear spring(s)/shackles, bent front frame rail (right side).

All of this has been identified, repaired and/or replaced during restoration. One of the things that I have yet to check, probably due to it's complexity, is the rear differential.

The pinion seal was replaced and yolk readisleeved; hub bearings and seals replaced and do not leak; driveshaft repaired and balanced.

Differential are fairly robust units but what would be symptomatic of something wrong? For example, a bent pinion gear or axle?

Suggestions would be appreciated before I take it into the shop for further assessment. GONZO

 

[Skip & Lynne]

Gonzo you have answered my long burning question. What car had a head on collision with mine YOURS. Seriously if there is no vibration or leakage fron the pinion seal or yoke and the rear end is quiet I wouldn`t suspect any problems. Skip

 

[gonzo]

Skip, that's it! Attempts have been made to isolate source(s) of intermittent vibration at speed. The usual suspects like wire wheels, tires, shocks etc. were sorted early on but that vibration still remains at 55 to 65MPH. Someone else in this forum summed it up nicely as "waiting for the shake" - quite true fo the Healey but maybe maybe it was a reference to living in California.

I understand that Scuttle Shake is common to the vehicle and this may well be the cause; however, the differential may be also contributing. How could this be isolated and checked?

Evidence suggest this Healey was dropped off some sort of embankment or cliff to only land safely on all fours, like a cat. This little mishap though managed to push the undercarrage up with such force as to cause the damage described.

This Healey is driven regardless of the vibration. My wish is for it to drive as good as it looks! GONZO

 

[Dave Russell]

Gonzo,

A solid big Healey with straight wheels & tires that are correctly balanced does NOT have scuttle shake. It is NOT common. A sometimes overlooked problem is brake drum balance, this has been a big problem on a few cars. A bent or out of index drive shaft can also cause shake.

To check for a bent axle housing, remove the entire differential center section, completely replace hubs & axles & visually check the alignment of the two inner axle stubs. They should obviously be centered with each other & in the center of the housing. Any misalignmemt indicates a bent axle shaft or axle housing. Rotating the axles individually will check for bent axles. A bent housing CAN be corrected.

A bent ring or pinion will make itself obvious in other ways, long before it could cause scuttle shake.

Shocks that are not in perfect working order can contribute to vibration. Any free play between the suspension member & immediate damping resistance of the shock hydraulics will allow for uncontrolled vibration of the wheel. If there is any lost motion in the shock links or dead spots in the hydraulic travel, vibration will be increased.

A few cars which have unrestored or improperly restored rust damage in the frame/subchassis will obviously shake more easily than a solid car. A problem sometimes arises when severely rusted structural parts are sand blasted & repainted. The paint does not replace the rusted metal, so structurally, the metal is still thinner than original & the chassis is more flexible. I have seen photos of "restored floor & structural sections" which obviously show deep cleaned out & painted over rust pits. These sections have no more strength than the thinnest rust sections, even if they look good. Sorry for the rant on "cosmetic only" chassis restoration. I have driven several new Healeys & a few "restored" ones. The truly restored ones, as well as the new ones, have no vibration at any speed. A couple of the clean & paint variety are remarkably flexible & vibration prone. Almost as bad as a TR6. Not all "restored" Healeys are the same, though the asking prices are often similar.
D