[95Chwagon]

Bumping my own thread for a related question. I know installing 4.10 gears can cause driveshaft vibrations in Impalas, but could you get away with a stock driveshaft in a Fleetwood with taller 28" tires? According to my back of the knapkin math comparing a 275/40/17 Impala tire to 225/75/15 Fleetwood tire, a 4.10 Fleetwood would spin the driveshaft like a 3.73 on an auto cross tire.

I have a spare 9C1 4.10/posi rear as a backup for my Caprice that has done nothing but gather dust for 10 years that I am thinking of putting to use. I drove in 3rd on the highway to test how it would feel cruising and no vibrations at any reasonable speed.

 

[BALLSS]

yes taller tire will neutralize RPM to an extent if running a lower rear gear....will that resolve what is a very common issue with a stock B body DS making vibrations with the lower gears, not likely but "some" have reported they get away vibe free with stock DS and lower rear gears (3.73)

what is against using a stock DS with lower gears is not only the comparatively low RPM they are balanced for and the fact the taper at each end thins the tube metal there making it inconsistent with the rest of the tube but also the diameter of the stock DS (rotational mass thing)....all those are addressed with a wider, straight tube, higher RPM balanced DS...like a Dennys 3.5 AL shaft

Good luck

 

[Marky Dissod]

... Installing 4.10 can cause driveshaft vibrations in Impalas, but could you get away with a stock driveshaft in a Fleetwood with taller 28" tires?
According to my back of the knapkin math comparing a 275/40R17 Impala tire to 225/75R15 Fleetwood tire,
a 4.10 Fleetwood would spin the driveshaft like a 3.73 on an auto cross tire.

I have a spare 9C1 4.10/posi rear as a backup for my Caprice that has done nothing but gather dust for 10 years that I am thinking of putting to use.
I drove in 3rd on the highway to test how it would feel cruising and no vibrations at any reasonable speed.

Consider recalculating with 235/75R15 (28.87")
235/75R15 is the OE-optional size for V4U, B9Q, & B05 - limos, hearses, & 'Armoured' Fleetwoods.
235/75R15 has several more tire options than 225/75R15.
Nearly every 235/75R15 tire option will likely outperform whatever 225/75R15 still has left to offer.

I've had the gaul to recommend 235/75R15 to several of my clients.
In every case, they fit fine with no clearance issues, and a pleasant surprise in terms of performance.
There's even at least one case of 255/70R15 (29") installed on a Caprice with no issues.

 

[95Chwagon]

I actually am currently running 235 75 15s for this very reason. I couldn't find the stock size with a white wall.