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| | | | Joined: Aug 2009 Posts: 152 'Bolter | | 'Bolter Joined: Aug 2009 Posts: 152 | I know remote diagnosis is difficult at best. Nevertheless, your help would be appreciated. There is a vibration in the shift lever of my SM420, which is in a '59 3800 with 261. What is the most likely culprit: u-joints, transmission bearings, or something else?
Thanks,
Oldbolter
1959 Apache 3800 dually flat bed/dump with 261
1956 3800 dually flat bed/dump with 235
1957 3600 flat bed, 350 engine, 700R4, PS, disc brakes, 14 bolt rear with 4.11 gears
| | | | | Joined: Aug 2009 Posts: 152 'Bolter | | 'Bolter Joined: Aug 2009 Posts: 152 | Yes, the spring is there.
Oldbolter
1959 Apache 3800 dually flat bed/dump with 261
1956 3800 dually flat bed/dump with 235
1957 3600 flat bed, 350 engine, 700R4, PS, disc brakes, 14 bolt rear with 4.11 gears
| | | | | Joined: Jan 2013 Posts: 1,518 'Bolter | | 'Bolter Joined: Jan 2013 Posts: 1,518 | When does it vibrate? which gears, idling in neutral, idling in gear with clutch in?
Check the first/reverse gear for rock on the main shaft (requires the mainshaft removal and disassembly), it should be no more than .015".
Also, check the shifting yokes for wear, the clearance between the shifting yoke/fork and sliders should be no more of a gap of .020, prefer .010.
I recently rebuilt a sm420 for a guy and it had a hell of a vibration in the shifter and on inspection I found both situations, the first gear was worn allowing a rock on the main spline of .040 and clearance on the 1st and 2nd shifter yoke on the first/reverse gear to be .035.
Last edited by sstock; 01/17/2019 3:12 PM.
1953 Chevrolet 3100261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done In the DITY GalleryVideo of the 261 running1964 GMC 1000305 Big Block V6, sm420, the next cab off restoration
| | | | | Joined: Aug 2009 Posts: 152 'Bolter | | 'Bolter Joined: Aug 2009 Posts: 152 | Thanks for the help. It looks as though I need to dig deeper into the trans.
Oldbolter
1959 Apache 3800 dually flat bed/dump with 261
1956 3800 dually flat bed/dump with 235
1957 3600 flat bed, 350 engine, 700R4, PS, disc brakes, 14 bolt rear with 4.11 gears
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