sm420 help (1 Viewer)

[cba]

I just received my adapter plate and have started assembly.
I am going by the extreme bends write up and I have run into a snag. With everything seperate I can easily turn the main shaft in the 420. When I get the t-case, adapter and tranny bolted together I can not longer turn the shaft. With a micrometer, the depth of the recess in the t-case for the bearing is .160 inches and the amount the bearing sticks out of the adapter is .199 inches. I think it is that difference that is killing me. Any one else every have this problem? Any ideas?

 

[Vortec_Cruiser]

If it's anything like the SM465 setup, which it probably is, then there is a thick gasket that goes between the SM420 and the plate adapter. This will space the plate far enough away from the tranny, so the plate doesn't press against the bearing. :

 

[cba]

Did your conversion require you to install the bearing retainer ring on the bearing furthest from the tranny. If I get a thicker gasket and don't use the ring it might work.

 

[Chef]

I haven't run into this with the 4 I've done...ping spaceghost, and the pirateboard...

 

[Chef]

You do have the bearing retainer snap rings all in place...?

 

[cba]

I didn't have it in place originally. I put it in and still get the same result. A guy at the local tranny shop suggested a thicker gasket between the adapter and t-case. What do you think?

 

[Chef]

Can you not turn it at all, or is it just "difficult?" Are you in gear in one or both boxes, or are they both in nuetral? I would expect a rebuilt unit in low/low to be difficult. On the rearmost bearing, are there any other retaining rings either from the rebuild kit, or leftover from before that are thinner? have you tried it without the retaining ring? Have you tried doubling the gasket between the plate and the tcase? Just some thoughts...

 

[cba]

It take two hands and I could barely turn it. I am in nuetral in the tranny and the input gear is not even on the t-case yet. No thinner retainer rings, trying a thicker gasket tonight

 

[SpaceGhost]

Didn't think of this till now, don't run the retaining ring on the second bearing, it's not needed. None of the bearings I bought included it.

The tranny bearing should be seated all the way against the case at the ring. The second bearing should be a tight fit (loose press) in the adapter, and on my tranny the bearing required some persuation to slide on the output shaft. The input gear will pull it up tight.

The washer/spacer you used is the TOY one? Seems odd that it spins freely with the adpater and both bearings and spacer in place, but when you add the tcase it tightens up. I'll be home in a couple of hours to take a closer look at one.

 

[cba]

Yes, the spacer is the Toyota one. The only thing I can think it would be is that maybe the depth of the recess for the bearing in the t-case is not deep enough. Suppose it is possible that Toyota did not mill it deep enough. Maybe a rough day on the assemby line back in '69.