1940 Buick 51
June 2022 - First good test drive!
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The steering column was repainted and reinstalled along with all the 3-on-tree column shifter linkages to the transmission. A short test drive commenced to determine the condition of the clutch.
The clutch pedal was almost all the way out before the car even started moving. And there was a lot of burning oil smoke. Turns out the clutch was bad and oil fouled. Now the worst part is the body is already on the frame and I did not want to remove it again to replace the clutch.
The clutch replacement would be done following the method vaguely outlined in the 1940 Buick factory service manual. Because of the torque tube, the process is not as simple as newer cars where one would just disconnect the driveshaft u-joint and drop it then pull the transmission back. The process is much more tedious but can be done in a home garage as I successfully did the job myself.
1940 Buick clutch replacement process
- Place rear portion of car frame on large jack stands (6 tons preferably) with jack stands near the flat portion of the rear frame before it curves up to the coil springs.
- Disconnect the following items:
- Rear shock damper linkage to frame
- Rear sway bar on both ends of axle
- Rear brake flexible hose from axle to frame
- Panhard rod
- Lower coil spring mounts at axle
- At this point, the entire rear axle is held in place only by the 4 bolts attaching the torque tube to the transmission. Proceed to remove the 4 bolts and then the torque tube should pull away free as the rear end is rolled back on the garage floor.
- Remove the 4 bolts that attach the rearmost transmission crossmember to the frame so the crossmember can be removed out of the way in order to drop the transmission. This crossmember attaches via a 2-bolt rubber mount to the support for the swivel "torque ball" joint at the rear of the transmission.
- Disconnect 2 gear shift linkages to the transmission by pulling out the cotter pins and washers.
- With a floor jack positioned under the transmission body, unbolt the 4 large bolts attaching the transmission to the bell housing.
- Pull the transmission back out of the bell housing and lower with floor jack. Service transmission as needed.
- Clutch fork is held in place by a cylindrical clutch release bearing support that is held in place by a beveled retaining ring. Pull these out.
- Remove all bolts on the perimeter of the pressure plate that attaches it to the flywheel.
- Clutch and pressure plate may now be removed as an assembly.
New discoveries...
The clutch was severely oil fouled despite evidently having been replaced because there was plenty of friction material. The pressure plate was original but had severe scoring on the surface that appears to be from when the original clutch disintegrated. For some reason a previous owner reused the damaged pressure plate.
Why was there oil on the clutch? Turns out the front shaft seal on the transmission that mates to the clutch was completely missing. Not disintegrated, just simply absent. At this point I decided to go ahead and reseal the transmission while I had it out. The rear shaft seal to the torque tube was also completely missing. The swivel "torque ball" seal and shifter seal were all worn out and replaced. Transmission gears were inspected and completely free of damage, and gear oil was changed.
I installed a new clutch and pressure plate from Bob's Automobilia with my back on the garage floor. The pilot bearing for the transmission front shaft to the flywheel did not need replacing fortunately. Reinstalling the transmission is difficult for 1 person so I had a friend over to help manuever the transission in place while I operated a floor jack to raise it up in place. Reassembly was largely the reverse of disassembly as described above.
And now a good brief test drive...
Now finally after all that work, I'm back where I started several months ago in doing a test drive. This time, much better!