Transmission Gurus: Main Drive Gear

H

Highboy34

Senior Member
On an assembled 39-48 closed drive transmission, on a work bench, if you grab the main drive gear forward of the front retainer, how much up-down movement should there be? I have one with about 3/32" of wiggle at the pilot bearing end and see rocking movement at its aft end at the synchro rings. I've not taken it apart for inspection, but will, and yes I have the excellent Van Pelt book. But in the book I did not see any discussion of up/down mainshaft movement. This ****** has .007" gap at the second gear washer, no fore-aft cluster gear movement and little or no fore-aft movement of the main drive gear, just the up-down.

The flywheel pilot bushing should keep it stable and centered mounted on an engine, but unmounted on a bench, how much rocking up-down should there be?
 
Make sure the bearing is clamped securely in the housing,most times they are loose on the retaining circlip area, also use a good quality bearing,AND the modern bearings have a metric width circlip that is trying to be clamped up in an imperial groove.Lawrie
 
Lawrie, I have the same question and have this situation using older components that predate the influx of metric bearings and circlips.
 
I have done this many times,it is very important to get it right,
If you do a search on this you should find the article I did.
if not let me know
Lawrie
 
I don't have a transmission nearby to check, but that movement you describe is not really relevant as the front of the shaft is supported by the pilot bearing in the flywheel. The question is, is the front bearing worn out? Any bearing will have some running clearance. This magnified about 2:1 at the end of the shaft.

The bearing does need to be supported properly so it will not slide back and forth. (As stated above). If the bearing is really held in there tight and you are seeing some movement I wouldn't be at all surprised.

If you know the bearing is in good condition you're probably good to go.

Mart.
 
This is not a spec that was ever defined by Ford or anyone else. We’ve always detected a certain amount of up and down movement when everything was assembled.....even with new ball bearing, new roller bearing, and a new mainshaft and main drive gear. The pilot bearing in the flywheel is the final piece necessary to hold the alignment.

Regarding the other comments about the retaining ring (snap ring, circlip, etc) I’ll repeat what we’ve stated before. The correct ring.....the ones made for the OD of the ball bearings....should measure .075 to .077” thick. When placed in the groove of the bearing, the OD of the snap ring should still fit into the machined recess of the bearing retainer (front or rear). These two snap rings control the endplay movement of the shafts that they support.

The typical aftermarket snap rings are not the correct thickness. We’ve seen them at .063” thick which will cause problems with endplay. We had to have a ring manufacturer make them to our specifications, which was the correct dimensions AND with the convenient opposed tips for your lock ring pliers. Don’t reuse old Ford snap rings unless you know that they are unused NOS rings.

Also, check the thickness of the bearing retainer gasket that you use.....too thick a gasket material would create a new endplay issue. Some of the aftermarket gasket sets supplied the two retainer gaskets in material that was 3 to 4 times the correct thickness. We stock BEST brand sets, which are of correct material.
 
Last edited:
You must log in or register to reply here.
Back
Top