1956 Buick Differential Rebuild

[Beemon]

I've been looking over the shop manual on this procedure as it's something I want to tackle this winter. I found a replacement for my old gears that doesn't have the hardening on the teeth worn off. I also talked to the shop that did it last (also the Dynaflow) and they'll do the swap for me for less than $300 (Not something I want to do nor have room to do in the driveway). I can save myself $400 in labor if I rebuild it myself, but the question is - how hard is this task? Consider that all I have is hand tools and a vise. I know the actual carrier bearings are a no-go on replacement, but I can get all the rest. Do the bearings generally need replacing (I would guess yes)? Or is it just a "make sure the seals are good" type of thing? Tips on setting depth? Point out I'm clueless? Fire away, please!

[MrEarl]

You and your never ending quest for challenges never cease to amaze me son. Personally I would probably elect to save the $300 and change it out in the driveway in a snow blizzard vs saving $400 by rebuilding the monster in a heated garage. I like what hair I have left. A wise man here once told me he would rather rebuild a Dynaflow any day than a rear end. 

But we may as well pop up some popcorn and get in our easy chairs 'cause this is gonna be interesting.  

[Guest]

The price seems okay but I wouldn't put the used rear end in without all new seals and bearings.  If you are having it apart then check it all and fix it.  Why take a chance and have to open it up again.  Once you have the carrier out of the car you only need normal tools plus a dial gauge and some blueing oh and don't forget the patience, patience and patience.  Make sure the pattern on the gears is right.

Personally I would do it all myself.  I put two clutches in a 53 Buick in crushed rock drive way, one in the summer and one in the winter both in Manitoba.

[Beemon]

I'll have to take a picture of my driveway when everyone is home to show why doing work that requires lots of room in my driveway is impossible lol. The replacement carrier is technically already out of the car, so I can start it tonight but have zero idea what to do other than follow the shop manual. If it just requires basic hand tools, then great. If I need some sort of press or puller, then I don't have either. I don't even know where you can find dial gauges anymore, there are never any at the auto parts store, hardware store, and I would rather skip on a Harbor Freight dial gauge (was gifted a HF caliper one year for my birthday, tossed it in the trash).

[NTX5467]

DON'T disassemble YOUR car until YOU know the "chunk" is a good one AND in good enough condition to be better than what you have now -- PERIOD !!

 

Most dial indicators and digital readout calipers will NOT be in the typical auto supply or similar.  The good ones might come from Summit Racing or another vendor that has "better" ones.  Harbor Freight or the similar Northern Freight stores do have some decent (read "hobbiest-decent") items.  Not nearly "garage grade" in many cases, but many garages might use them for ease of access and less $$$.  Check out specialty tool stores, but they might be a distance away and cost more.

 

With all of your desire for "investigations" and such, you might find a buddy and go in to rent a space to work on your cars AND keep them there.  No issues with "driveway" congestion AND "out of the weather".  If something doesn't work right, you lock the door and walk away for a while (even a few days, if needed!).  Every "car guy" needs "a hangout" of their own or one they can use.  You can get more help that way, too!  Just presume anybody that comes around might want to help . . . that's all it takes.  The good ones will come back.  Some basic tools, a decent air compressor, HEAT and cooling, a few old comfortable chairs, and a small used refrigerator will help for general use and those times when "pondering" is needed.  Nothing fancy so that if something might get broken, not a big $$ loss.  You can see the scenario.  About 20 wide by 40 deep.  Hopefully with "facilities"!

 

The side issue I see is that with all of the projects on your ONE project car, it might give somebody the wrong idea about Buick dependability and long-term life!  I understand and greatly appreciate the family ties to that car, too!

 

NTX5467

 

 

[Beemon]

18 hours ago, NTX5467 said:

DON'T disassemble YOUR car until YOU know the "chunk" is a good one AND in good enough condition to be better than what you have now -- PERIOD !!

 

OLD:

 

 

 

 

 

NEW:

 

 

 

 

 

The only difference is that they are 3.23 instead of 3.36 - 3.36 gears are apparently rare even though the 3.23 gears were only in the Special.

 

A hang out would be pretty cool, it's just hard finding like minded individuals my age that are into classics. Nothing wrong with the old boys, except relateability. By that I mean a lot of guys my dad's age drove these cars as kids, grew up around them, and I didn't... so it's a little big different. Especially when you walk into every conversation with them assuming you know nothing and then listening to a 20 minute lecture because you're being nice on how to research, maintain and repair a car.

 

Can't argue with dependability. My Buick has maybe broke down once, but I can't fault the car - the pertronix fried from a voltage spike that stranded me at school (should have listened to Willie!). Oh, and the starter fiasco. I just want to get rid of the howling banshee with this one!

 

My many projects are my way of catching up to the old guys. I need to experience everything in a span of a few years that took others decades of enjoyment just to fit in!

Edited December 20, 2016 by Beemon (see edit history)

[Ben Bruce aka First Born]

Ben, you are wise beyond your years, IMO.  This old man would be proud to hang out with you.

 

  Merry Christmas.

 

  Ben

[Beemon]

Thanks, Ben. I would love to meet all of the guys on this board that has answered all my annoying questions and threads thus far. I'm actually going to try and make the great pilgrimage this year if the stars align with my pocket book lol.

 

Back to the diff, I guess my biggest question is will I need more shims or will I be able to get away with putting the exact same shims back from where they came and still get the same depth? How hard is it to set the pre-load? I understand the preload chart, we had done similar in Mechanics of Materials. Is it difficult to pull the bearing races off of the pinion shaft with a punch and hammer? Lastly, should I bother dismantling the spider gears if there aren't replacement differential carrier bearings available?

[Ben Bruce aka First Born]

 

  Wish I could help. I installed a '55 century 3:36 in my '50. Just pulled the assembly from my housing and installed the assembly from the '55. New seals and gaskets only.  8000 plus miles later still quietly doing it's job.

 

  Ben

 

[NTX5467]

6 hours ago, Beemon said:

 

Back to the diff, I guess my biggest question is will I need more shims or will I be able to get away with putting the exact same shims back from where they came and still get the same depth? How hard is it to set the pre-load? I understand the preload chart, we had done similar in Mechanics of Materials. Is it difficult to pull the bearing races off of the pinion shaft with a punch and hammer? Lastly, should I bother dismantling the spider gears if there aren't replacement differential carrier bearings available?

 

The side bearing shims center the differential case in the housing for a PARTICULAR ring gear and pinion gear combination.  Just changing bearings?  Remove AND account for EACH side!  There will be a thicker shim and a variety of thinner shims in EACH shim stack.  IF you disturb that total combination (RGP and case), then you'll need a different shim stack combination.

 

Pinion bearings are best done with a press mechanism, for removal and installation.  Spider gears usually come in a SET, the shaft can be a separate item  Totally different labor op from anything else mentioned.  There are some washers in there, usually, plus the locks which hold the axle shafts to the differential unit, typically.

 

IF there is a "crush sleeve", you'll need a new one AND enough air ratchet torque to put it to the basic torque, then a lonngggg cheater bar and a high-capacity torque wrench.  In more current times, the crush sleeve has been replaced by a solid spacer.  The disassembly torque is measured and then used as the final torque setting upon reassembly.  But this is for more-current production units, not the earlier ones.

 

Once the unit is assembled, the dial indicators will help with the set-up as the dial caliper will help in measuring the side bearing shim stack dimensions.  When done, "gear marking compound" (i.e., "yellow lead" or similar) is used to check the final tooth contact pattern, forward and backward, to ensure all of the gear tooth contact patches are in the correct place..

 

As First-Born did, if you find a good "chunk", that's the easiest way to do it.  Minimal time, minimal labor, possibly best outcome.

 

WHEN you get energetic, you might work a deal with your salvage yard associate to loan you a GM rear axle from a car they're getting ready to crush so that you can self-learn about how it all fits together and works?  Just like getting an old hood to hone your sanding, refinishing, and painting skills.  Maybe even a door and deck lid, too?  Your OWN vocational-technical 'lab"!

 

Happy Holidays!

NTX5467

[Beemon]

I'm not entirely sure what the big difference between the 55 and 56 rear diff is except for spline count, but the seal is behind the retaining nut. I'm not sure I'll be able to replace just the seals without removing the retaining nut. Won't I have to do a rebuild at that point since the pre-load will be different with the old bearings?

 

Willis, as always, your knowledge is greatly appreciated! There isn't a crush sleeve on this diff. I found that out when they tore into the original one and we found the tin foil teeth. If a press is involved, then I'm at the mercy of the shop. This is one piece I don't want to bang on. I know they made them "bullet proof" but even the best bullet proof vests can't stop blunt force trauma. I just checked the unit before writing this reply, and it all turns freely (no scraping or scoring noises). The pre-load retaining nut has a huge slot punched into it, though. I'm guess it cannot be re-used?

[Leif Holmberg]

Here you can see the differens inside from earlier year 1955, and the 1956 and later rear axle with much more splines but much worse.

Leif in Sweden.

[old-tank]

If the new rear looks good and 'feels' good, just go ahead and install.  The pinion seal is probably defective by now and the pinion nut will be scored by that original leather seal.  Seal the torque tube to rear interface well and the leak from the pinion seal will find a level in the torque tube below the driveshaft.  Drill a small hole into bottom of the torque tube just in front of the rear flange.  Tap the hole for a small screw to serve as a plug.  Monitor the fluid in the torque tube:  if thick rear end fluid , leave it there; if tranny fluid, address the seal at the front of the torque tube.

[avgwarhawk]

Just the smell of 90 weight gear oil is enough for me to have a shop do it for $300.00.  

[Kosage Chavis]

 Too bad you live all the way in WA bruh.  I know we could exchange some ideas on working these Buicks.  There is literally no one around my way that works on Buicks or has the knowledge base that the folks have on this forum.  This specific project is interesting though.  Good luck.

[Beemon]

10 hours ago, avgwarhawk said:

Just the smell of 90 weight gear oil is enough for me to have a shop do it for $300.00.  

I think 85W140 would be more appropriate?

 

Even though I have all the bearings and seals right now, I think I will pay for the straight swap. I'll disassemble my old unit and put that one back together, and then when the new unit starts to fuss or leak or whatever, then I'll know how to do it without experimenting.

[avgwarhawk]

44 minutes ago, Beemon said:

I think 85W140 would be more appropriate?

 

 

All the weights smell horrible to me!  I do use 85W140.

[old-tank]

58 minutes ago, avgwarhawk said:

All the weights smell horrible to me!  I do use 85W140

not near as bad as the original lube.

[Beemon]

Wasnt it whale oil? My grandfather did the rear end job in the sixties so I was not blessed with the experience. 

[Daves1940Buick56S]

Benjamin: I have been down the differential rabbit hole so some advice from this sadder-and-poorer-but-wiser Buick guy. I started out with the stock 4.44 rear on my 1940 56S. It was OK but I wanted to lower engine revs, so I started looking for a rear with a more favorable ratio. Well, I found one that was around 3.4 from 1954. I do most of my own work but draw the line at rear and transmission work - I did that when I was 19 but not now! So the guy who was doing the work took a look at the "new" rear and said, it looks OK but will not know for sure until it's in and adjusted. It needed all new bearings (carrier and pinion) so I went ahead and had the outer axle bearings done as well.

 

Upshot: too worn for proper adjustment, when he put the yellow lead it showed full spread pattern. Basically it wailed like a banshee. So I stuck with that while I looked for another. After 2 tries (purchased but not installed) I finally got one that was good, a 3.6. It's in there now and very quiet. No new bearings needed other than pinion. In summary, keep at it, you may get a bum diff but keep looking, they are out there. Go ahead and replace the outer bearings while you have the half-axles out.

 

BTW, there are young people interested in these cars, just in small numbers unfortunately. My current "assistant" is 11 (and a half, as he would say!) and loves these cars, and working on them. I basically explain what I want done, and he does it, with my supervision of course. Last Feb/Mar when he was 10 he pulled the head on my '40 (see attached).

 

Cheers, Dave

 

 

[avgwarhawk]

8 hours ago, old-tank said:

not near as bad as the original lube.

 

I believe the lube when I replaced it a few years ago may have been original.  It stunk the high Heavens.   

[old-tank]

10 hours ago, Beemon said:

Wasnt it whale oil?

There was sperm whale oil in the original, but the smell is from sulfur compounds.  The original also contained lead soaps that are highly toxic, so maybe it is a good thing it stinks so bad.

[NTX5467]

In prior times, as with motor oil back then, higher viscosity numbers equated to better high temperature protection.  "90 weight" is the typical car rear axle lube.  Some might have taken higher numbers than "90".  The 85W-140 is a multi-vis product.  Rear axle lube used to be "forever", just add as needed.  Now, with the better synthetic lubes, there is a change recommendation for some brands . . . as some brands also recommended change intervals with the normal stuff.

 

That smell?  Took ages to wear off of bare skin!  Some of the newer-spec GM oils state they have a grape smell, according to the label on the bottle.

 

Pennzoil, for example, now has 80W-90 for normal rear axles.  The synthetic is 75W-90.  I think I'd go with the 90 viscosity rather than 140!  Reason?  Power consumption, especially in cold weather.  As long as the seal rubber is compatible with synthetic oil AND has the correct "GL" spec, no reason why it couldn't be used for its better pourability at 32 degrees.  That's just me.

 

NTX5467

[Beemon]

I was just always told that used rears prefer 140 and new rears like 90. Something about thicker oil taking up slop until the gears find their happy place warmed up. Probably the same reason why people stuffed wood chips and banana peels in the diff.

 

Also merry Christmas everyone!

[NTX5467]

Consider, too, that the rear axle lube ALSO provides lubrication at each end of the axle tubes, too. 140 wouldn't get there quite as easily as 85W-90, typically relying on turning corners to get there, as I understand it.   And then there's "cold weather" and what that typically does to gear oil! 

 

Other side of things is that if a gearset is worn enough to need 140 lube, it probably needs more than thicker oil to keep it quiet.  And then there's an "Andy Griffith Show" episode where Barney purchases a '54 Ford from an allegedly reputable used car dealer.  The "little old lady" special.  He and Andy and their dates went to Mount Pilot to see a movie and didn't make it back before it wouldn't move any more.  "Sawdust" found where it wasn't supposed to be, as I recall.

 

There was a "rule" that the harder you ran a mechanism, the more internal clearance it needed for the moving parts.  In the case of engines, it would be piston clearance and maybe a smidgen more on bearing clearance.  And, sometimes, thicker lubricating oil . . . in a time when higher viscosities usually meant stronger "film strength", but with modern basestocks and synthetics, more viscosity isn't always best.

 

And then there was the case where a local guy had a '76 TransAm.  It got a bearing knock in it, so he added a popular (viscosity improver, "raiser") oil additive.  That one can helped, so he added another.  MAJOR knock and engine repairs resulted.  With the 20W-50 motor oil he used, we estimated the resultant mix was 40W-70. 

 

NTX5467

 

 

[old-tank]

I use 85w-140 in all of mine (and i ain't changin' ) including the manual transmission of the F-1.  I had some 75w-90 in one of the Buicks for a few thousand miles and that stuff seeped out every gasket interface and bolt threads...never dripped, but was a sloppy mess.  55 axle bearings are packed in grease and have seals on both sides; 56 has sealed bearings.  Back when the F-1 was a daily driver and I was using 90 in the transmission, I could not shift it in 20* weather until it warmed up; in fact it would not crank unless the clutch was depressed and would die after starting if the clutch was let out in neutral...changing to 85w-140, I never had any more issues.

Willie

[NTX5467]

(Guess I've been around too many non-Buick rear axles, at work and otherwise?  If the bearings are packed in grease, is there a "repack" interval or is that when the bearings are replaced?  Just curious.)

 

Thanks for those clarifications, Old-Tank!

 

NTX5467

[Aaron65]

12 hours ago, NTX5467 said:

(Guess I've been around too many non-Buick rear axles, at work and otherwise?  If the bearings are packed in grease, is there a "repack" interval or is that when the bearings are replaced?  Just curious.)

 

Thanks for those clarifications, Old-Tank!

 

NTX5467

According to my owner's manual, you're supposed to pull the axles and regrease the bearings every 25,000 miles.  I'm going to guess that didn't happen too often.

[JohnD1956]

I believe that prior to 56 there was a rear cover on the differential.  I don't know if those rear axles needed "C" clips to keep them in.  But 56 was the first year for the pressed on bearings and no "C clips were used.  It is too bad that the fine spline on the 56 driveshaft turned out to be so vulnerable.  It's the reason I was able to get my 56 back in 1975.  The original driveshaft had spun and the owner could not find another before the rains came and flooded the car.  Lucky for me I had the rusted out Roadmaster and the assembly was a bolt in operation.  

Edited December 26, 2016 by JohnD1956 (see edit history)

[old-tank]

41 minutes ago, Aaron65 said:

According to my owner's manual, you're supposed to pull the axles and regrease the bearings every 25,000 miles.  I'm going to guess that didn't happen too often.

55 manual says 20,000 miles and probably did not get done unless the original leather seals were leaking.  With modern seals and lubricants it is probably for most a do-it-once chore.  The one 56 that I saw a rear bearing being replaced, the new bearing was sealed.

[MrEarl]

 I have not seen mention of this Buick motor division rear end service manual for 1956.  It goes into pretty good detail of disassembly and reassembly testing,specifications, tolerances, adjustments and tools used  and the best part with good illustrations and pictures.  I can get it to you for possibly copying and return to me if interested Benjamin 

 Well  imagine that! All 8 uploads failed, this is getting old!

 Benjamin, if you're not familiar with this book and want to see pictures of what it is PM me your email address and I will send a few 

[NTX5467]

Can you scan the pages and send those scans to the CD drive, then "disc" them?  Just curious.

 

My aunt and uncle bought a new '56 Special (white over black, red guts, 3spd manual) in Trenton, NJ on their way from Newfoundland, driving it back to their home in TX . . . in 1956.  He didn't hot rod it or anything, but as the car aged, there seemed to be rear axle problems every few years.  The last time, he parked it by the road where they lived.  A "route bakery supervisor" bought it, problems and all, and put a '57 unit in it.  End of problems and the new owner was HAPPY.

 

At the time it sounded a little strange to me for the recurring issues the dealer couldn't fix and stay fixed.  Might have been the rr wheel bearings, considering the recurring nature?

 

NTX5467

[MrEarl]

There's a lot of pages to scan but I think it would be worth it so will try and find time. 

[Beemon]

Even though differentials interchange between 56-60, the 57-60 differentials are different. I tried locating a 58 3.23 differential but was unsuccessful. I still have a lot of time, but the time these cars are around seem to be diminishing rapidly with all the yard closures in the last couple years. 

[Guest]

6 hours ago, Beemon said:

Even though differentials interchange between 56-60, the 57-60 differentials are different. I tried locating a 58 3.23 differential but was unsuccessful. I still have a lot of time, but the time these cars are around seem to be diminishing rapidly with all the yard closures in the last couple years. 

How bout a 57-75series or a 58 limited per my power seat post?  Shipping's the killer on that one perhaps?When Buick changed to the 364 in 57 they put stronger gears in the stick trans. Isn't it plausible that they considered the same issue with the rear end assembly? I think those fine spline drive line connecters really proved the wrong direction as well, as I talked with a few folks who had 56 sticks that changed those out. End of problem. PM if curious on cost please. I think you'd be pleasently surprised. I would think those two luxo-rides would have the highway ratios your seeking. It's cold here so it wouldn't be a hurried acquisition that's for sure. Oh, and did I mention I'm old? Brrrrr! In taking these Buicks apart, I've noticed the more expensive when new the better shape the mechanical parts generally seem to be in when I find them now. Kinda logical when you think of price paid up front and care and feeding affordability on going and gentilness driven while on the road. Might be coincidence, but I don't much believe in those! Just sayin'.

Edited December 28, 2016 by Guest
Dimbulb (see edit history)

[Beemon]

Thanks for the offer! I'll definitely PM you about that rear end if the one I habe doesn't work out for me. Do you know what the gears are by chance? I know highway gears are always preferred but the differential also absorbs a lot of moment forces and if you go too light, you run risk of mechanical failure. 

[NTX5467]

I somewhat doubt the basic design torque capacity would be decreased with the highway ratios vs. the "other" ratios.  What would change is "acceleration" from a stop, although once moving, it would not be so noticeable and "kickdown" (and all that might imply with DynaFlow Drive) will be there at higher road speeds.

 

I'll concur that the nicer upper-level models could possibly receive better ownership care than a base model of a similar vehicle might . . . all things considered.  And then some buyers "squeaked" too much to spend anything that was not absolutely necessary on the particular vehicle . . . which might be how they afforded the nicer car to start with.

 

NTX5467

[Beemon]

14 minutes ago, NTX5467 said:

I somewhat doubt the basic design torque capacity would be decreased with the highway ratios vs. the "other" ratios.  What would change is "acceleration" from a stop, although once moving, it would not be so noticeable and "kickdown" (and all that might imply with DynaFlow Drive) will be there at higher road speeds.

 

Not engine torque, rather the torque multiplication on the axle shaft and drive shaft in regards to a ring and pinion. It's like blowing you third member by over revving if it's under sized or not strong enough to take the torque on a drag take off. Even though the Dynaflow is a serious hog when it comes to power, going down to a 3.03 or 2.67 or whatever lower end gears they used in later years could be problematic for the current setup. The 1956 was engineered to take 3.36 gears with high compression and 3.23 with low compression. The transmissions are also different, as well, and could be that those gear ratios are best suited for the 56 Dynaflow since 3.36 gears never show up again in a Nailhead buick after 56. Plus we also know the spline connection at the pinion is also weak. So if lower gears are used, and more energy is required to take off from a red light, then there's just more shear force added to the pinion and possibly the ring gear, or both. I'm probably over thinking it, so I defer to KISS and want to stick around 3.36-3.23 range.

[NTX5467]

You ALSO need to look at the tire sizes used with those particular rear axle ratios.  Taller tires need lower gear ratios to be the same as slightly shorter tires and the similar higher gear ratio . . . to maintain similar cruise rpms or MPH/1000rpm.

 

Certainly, there is some optimum number of splines (and related DEPTH of the splines!) for a particular material and shaft diameter.  More splines allow more surface area to transfer torque through.  In the world of Ford 9" rear axles, the stronger ones are noted to be the "more splines" axle shafts.  I know I'm mentioning "axle shafts" whereas the Buick reference is for "pinion shaft", but I suspect the basic principles apply.  Several variables in this mix!

 

When I was mentioning "design torque" it was for the rear axle unit, not engine torque.

 

In the world of ring gears, the gear teeth are all pretty much of the same depth and thickness.  What changes is the thickness of the basic ring gear mounting flange on the axle's differential housing.  The thickness has a particular gear ratio spread it woks with.  In the aftermarket, the ring gear is of a particular thickness, but a spacer is used to compensate for the lack of thickness of the differential case's ring gear mounting flange.  I would suspect the OEM gears are of the better materials, with the aftermarket gears being of slightly inferior metal, but heat treated or similar to get the strength back to where it would otherwise be.  Different surface "look" and "ring".

 

Any shockloads would possibly be intensified by wider clearances between the ring gear and pinion gear interface.  The amount of pinion gear thrust washer wear would be an issue too!  I believe that "spec" is termed "backlash"?

 

The Triple Turbine DynaFlow used te 2.78 ratio in 1958, I believe.  The normal DynaFlow used the 3-series rear axle ratio . . . from what I found a few days ago.    At a time when a Ford Galaxie 500 with Cruise-O-Matic used a 2.69 and the single-range Ford-O-Matic used a 3.10 ratio.  The "luxury" was a "big motor" and lower cruise rpms via different rear axle ratios.

 

NTX5467

[Guest]

On 12/28/2016 at 5:32 PM, Beemon said:

Thanks for the offer! I'll definitely PM you about that rear end if the one I habe doesn't work out for me. Do you know what the gears are by chance? I know highway gears are always preferred but the differential also absorbs a lot of moment forces and if you go too light, you run risk of mechanical failure. 

The gear ratios would have to be checked, as would condition. The biggest enemy I've seen when removing the rear covers is not wear or breakage, but condensation causing rust. They sit so long without turning the upper half is very rusty and the bottom half perfect. Temp change really kills them promoting rust as gravity finally drains all the protective lube off the top of the diff.