Pinion bearings replacement - 37 Special

[70sWagoneers]

Hello again,

My '37 Special has started emitting a pulsing roaring sound from the back end. I jacked the car up, put it in 3rd gear, and went around to listen. At first, I hoped it was a wheel bearing because it sort of seemed loudest out at the right wheel, but that may just be the brakes rubbing a bit more over there. If I get under the car and feel the pumpkin I feel a sort of pounding or bumping. If I turn the car off, in neutral, and spin each wheel, I dont really hear any harshness or roughness. So... my guess is the pinion bearings. That sound about right? What kind of ordeal is it to just replace the pinion bearings?? Or can anyone recommend a rebuilder near the Mooresville/Charlotte NC area I could talk to? I'm not opposed to doing this myself; I dont have a lot of money and I like to do things myself. If anyone can post some diy info and or tips I'd appreciate it. So I will continue to research this issue and take into account what yall say. The car is parked for now until I fix the problem. And as a wish list item... I see people replacing their rear axles with lower gear ratios, can you just replace the pinion/diff set?

Thanks

James C

Edited July 21, 2018 by 70sWagoneers (see edit history)

[DonMicheletti]

That noise can be any number of things from bearings to gear failure. In any case the torque tube rear end is a PITA to get out and work on.

Step 1 would be to drain the differential, pull the cover and see if there is anything obvious. Pry stuff around and see if there is any strange play in things.

[Spinneyhill]

Here is a wild thought....

 

In my 1930 Dodge 8, the ring gear bolts were set up in pairs with a steel plate under each pair, with the ends bent up as a locking tab. One day, without warning, a bolt broke. Luckily it didn't go through the pinion-ring gear but dropped to the bottom. Clearance is small so the ring gear rammed it through the bottom of the rear cover (with a good bang that woke me up).

 

I found that all the ring gear bolts were loose and all the tabs were bent up against a face on the bolt. How did they loosen without moving the tabs? 

 

Anyway, is it possible yours are working loose too?

[MCHinson]

I don't think that the 1937 and 1938 differentials are identical but if it might be possible and relatively easy to do a complete swap from a 1937 to a 1938 40 series torque tube and differential, I have a 1938 40 series differential and torque tube on a 1938 Special chassis that I am about to scrap. I am a few hours away from you in Wilmington. If you find that you can use it, I would rather let you have it than send it to a scrapyard.

 

If you want to do a lot of reading on the subject, the old Torque Tube issues have many articles on different differential swaps. A lot of them involve a lot of work. 

 

They are a bit difficult to navigate, but click on the technical article index, and that will give you the issues that you want to read. 

 

http://1937and1938buicks.com/The-Torque-Tube/The-Torque-Tube.htm

 

 

[pont35cpe]

James, I agree with Don. Pull the rear cover and inspect, also check for metal shavings in the oil which could destroy all the bearings. If you are lucky the noise may be an axle bearing or carrier bearing, these can be replaced with rear-end in the car. `37 is the first year for the hypoid type gears. The main difference I`m aware of between `37 and `38 is `37 has leaf springs where `38 has coil springs, so mounting brackets on the rear housing would be different. Mounting brackets could be removed from the `38 housing and the `37 leaf spring brackets welded on. The torque tube assemblies may be interchangeable and both being Specials the torque tube assemblies should be the same length, if so, you should take Matt up on his offer.. 

[Spinneyhill]

Republic Catalog shows '37 80 and 90 series still spiral bevel. 40 and 60 series were Hypoid as above.

[70sWagoneers]

Alright, so no visible damage in the rear pumpkin. No debris. The gear lash is a bit loose but thats understandable. The spider gears have some freeplay but theyre not making the noise. So it must be something forward of the pumpkin. It sort of sounds like a mild roar with intermittent clunks like a bearing ball has gotten loose or disintegrated. Is there a bushing or bearing in the front of the torque tube? Or it could be the ujoint at the back of the transmission? Well it all got to come out anyways to find out for sure! So anymore advice is appreciated such as where to source parts like crush sleeves and shims or advice on getting the axle assembly out.

 

I dont have much time to work on it right now but im goimg to keep researching.

[Bloo]

1 hour ago, 70sWagoneers said:

It sort of sounds like a mild roar with intermittent clunks like a bearing ball has gotten loose or disintegrated.

 

They do that.

1 hour ago, 70sWagoneers said:

Is there a bushing or bearing in the front of the torque tube?

 

Probably. I forget how Buick handled the front of the torque tube. Whatever is up there has to run fairly tight or it will make noise. Chevrolets make a drumming noise with only a slight bit of play.

 

1 hour ago, 70sWagoneers said:

Or it could be the ujoint at the back of the transmission?

 

Those are picky about lubrication and often don't get much if the torque ball leaks badly.

 

1 hour ago, 70sWagoneers said:

So anymore advice is appreciated such as where to source parts like crush sleeves and shims

 

No crush sleeve in this. Shims probably need to be sourced from a junk rearend. Chances are pretty good you wont need to shim it differently if you are just changing bearings.

 

If I were you, I would check the backlash carefully before you take it apart. Also check the contact pattern, and make notes. Others may disagree, but I think you should put it back the way you found it, maybe with a slight correction to the pattern if it is bad. Tightening the lash back up to factory spec would only make it have to break in again, and with wear it might be very tough to get a good pattern at a new lash setting.

 

That might all go out the window if the carrier bearings are bad, and the ring gear has been flopping around. In that case you may have to take a best guess. GM liked to use ball bearings on carriers because they owned New Departure. Probably that wasn't the best choice. It wouldn't surprise me at all if they are bad.

 

Your pinion will have either a couple of ball bearings, or a ball bearing and a Hyatt bearing. Those could be bad too. Plan on changing all the bearings, and consider it a pleasant surprise if you don't need to.

 

[DonMicheletti]

The carrier bearings are Timkens. The pinion has a roller bearing at the gear and a double row ball bearing at the front to take the thrust.

There is no bearing in the torque tube at the front flange. But there is a bushing the U joint runs in at the torque ball that could be bad. As mentioned, it could be a bad U joint.

[Bob Engle]

While it's a pain to pull the differential, getting the gearmesh correct is is bigger pain.  there are setup tools for this job, but finding someone that has them is a problem.  You want to mark the carrier bearing position so you can get the ring gear back in the same location.   Usually you would take a measurement from the end of the pinion shaft to a straight edge across the carrier bearing caps.  If the thrust bearing is bad, you can't get a usefull measurement.  It's then  a process of gear mesh backlash  and gear mesh contact pattern.  Don't be in a hurry, get the lash and contact correct.

 

Bob Engle

 

[mcdarrunt]

I have everything from the rear of the block to rear end out of my 37 Special. The transmission is inside my storage shed and the rear end is out back in the scrap pile. Been there for several years and if the open end of the torque tube is facing up it's probably junk but shipping cost would transfer it to your possession. At the time it was pulled I had just made a 2000 mile trip and decided the 4.44 gears had to go.

[Bloo]

FWIW I am going through a rebuild on a Pontiac rear axle of similar design, and parts have been a huge problem. I have 3 disassembled axles here, and still not quite enough good parts (and I have a brand new ring and pinion and bearings).

 

Based on my own recent experience, If I were you I would be jumping up and down to take mcdarrunt up on his generous offer. You never know what you might need.

[Jim Nelson]

I had a 37’ coupe that I just sold.  I changed the third member to a 3.41 : 1.   It is a 1954 third member.  A 3.6 ratio is also a good road gear set.   It was a bit more expensive a swap.   My ‘38’  has over drive.  Of the two, the OD is less expensive.  While installing the OD  in the torque tube, you can (should) replace the pinion bearings.  This lets you replace the outboard axel bearings while its apart.   I can garantee that the outboard bearings have not been serviced since it was built.  My carrier bearing were like new.  If you want to renew the rear and keep the 4.44 gears for hill driving,  the overdrive option is the best.  IMHO,  I now drive my  ‘38’ with OD and cruise 65 mph while turning 2350  rpm.   Details , pix to show.  Oldbuickjim@gmail.com.