'50 Stepdown Rear End Backlash - Tips?

50ClubCoupe

I was experiencing some vibration when the car hits 35-40 mph and I get a pretty good 'clunk' when engaging first gear so I just pulled the propeller shafts and replaced all the u-joints as well as the carrier bearing.  The u-joints didn't seem bad and didn't have much grind/play in them and the carrier bearing only had the slightest bit of movement so, while it may cause some vibration, it didn't seem consistent with the magnitude of the issue.  So, I went to the yoke on the differential and noticed a good bit of backlash/slop when turning the yoke.  With the wheels on the ground, I can turn the yoke from a 12:00 position to almost a 2:00 position.  That seems excessive.  After checking the technical manual it looks like I have to pull the axles and then remove the carrier in order to (hopefully) adjust the tolerances to within spec.  Are there any tips or tricks anyone has to making this job go a little easier, or perhaps a list of parts that should/could be replaced while I have everything apart?  I'm planning on replacing the carrier housing gasket as well as the pinion seal but was wondering if it also necessary to do the seals on the axles. Any advice would be appreciated….the job looks to be a real pain in the 'rear-end.'

RichardD

Scott, type 'pinion' into the search box upper right; that will give you lots posts that have that word. Perhaps some of those could give you info and encouragement~~~

R

Geoff

Leave the  diff gears alone.  They will not be causing vibration. Check the axle shaft nuts, that may cause a clunk if they are not done real good.   Get the drive shaft balanced. 

Geoff

Also the pinion flange nut must be real tight.  

bob ward

If the axle shaft or hub keyways are worn or if the key itself is worn that can give you a clunk even if the axle shaft nuts are done up to spec.

Uncle Josh

And replace those two rubbers that mount the center bearing.   Old ones will give you a vibration

50ClubCoupe

Thanks to all who have replied thus far.  I appreciate the list of items to check and I'm now a little more optimistic about the differential....I was really hoping to avoid that tear-down.  Since no one has voiced any concern over the amount of slop, I'll leave the differential as-is and address the other items that have been mentioned.  I plan to eventually swap out the rear for a dana/spicer with a better ratio and maybe add an O/D transmission so my current setup should get me by until that point. 

Per

Scott, What ratio do you have now? If it is 4.10, and you put in overdrive, you will have a good setup for driving 70 without overspeeding the engine. Per

bob ward

To add to Per's comment, the step-down overdrive boxes have a 30% reduction which makes a 4.11 diff into a 2.88 compared to the dana 3.08 found in hydramatics.

50ClubCoupe

I'm 90% certain that I currently have the Hudson built 4.11 in my non-OD '50 Commodore.  After speaking with some local club members I've found that switching to a Dana rear will allow more gearing options as well as more plentiful parts availability so I was considering that route.  There was some discussion but some felt that an OD with the 3.54 dana/spicer would be a good combination.  I've got some time before I really put some more thought into it but that combo seemed reasonable enough.

Park_W

I think you might find 3.54 with OD is a little "over-geared," unless you live in flat country.  I tried 4.11, 3.58 and 3.73 with my '51 Hornet, and found that 3.73 with the OD was just about right.  Fairly low engine speed in OD, but able to take the hills on the Interstate without lugging or kicking down out of OD.  3.58 to 3.73 doesn't sound like much of a change, but the performance difference is significant.

50ClubCoupe

Thank you Park, good insights.  It was a pleasure to meet you at the Walker meet. I hope to spend some more time with the group at future meets.