46RH OD Shift flare?
 

Anything other than putting the OD one way clutch in backward that would cause a 1-2 second rpm flare when shifting into OD? Finally got the wife's truck running with the cummins swap and 46RH that I rebuild with some upgrades and lockup, and the good news is that everything else seems to work ok, but it's definitely unloading during the 3-4 upshift for a second or 2. My research seems to indicate that the only way it would do this is if the OD one way clutch isn't working for some reason, most likely because it got put in backward but I'd like a second opinion. I remember there's also a measurement for the OD piston thrust plate that's important for the OD shift, is there any way this being wrong would cause this problem? I did some creative fiddling to measure this without having the special tool and I'm reasonably confident it's right but could certainly have goofed.

Not looking forward to tearing it back apart... just got done with this thing finally! Only been 2 years or so since her truck has worked reliably, and 6 months I've been working on the swap. Good news is it run nice, and I guess fixing the OD housing is easier than having to tear the whole bloody thing apart, but still....

I don't know where you get your research from but it's pretty impossible to install the over running clutch backwards. Secondly it is not going to cause a delayed shift. It either works or it doesn't. That clutch needs to hold for the three forward gears and freewheel for O/D and reverse so putting it in backwards would cause the trans to not work at all.

If you had a complete transmission you shouldn't have needed to even mess with the O/D piston spacer. You either have too thin of a spacer, a cut O/D piston seal, incorrect number of clutches and steels or the O/D piston's bleed orifice is clogged or blown out.

So I'm missing something here then.

The symptom I'm seeing is an increase in engine rpm for 1-2 seconds during the shift from 3rd to 4th. Shift timing, function once in gear seem ok. The 4-3 down shift also seem to be normal with no flare and correct timing.

My understanding of the system function is that during the upshift pressure is applied to the piston causing it to first release the direct clutch and subsequently apply to OD clutch, and during this time the one one way clutch locks up and maintains power flow during the short time the direct clutch is released and od clutch not yet applied. Unless I am much mistaken, the only way I would be getting a flare during this shift is if the one way clutch isn't working.

A piston seal problem or incorrect clutch setup seems like it would cause failure to engage correctly or issues on the 4-3 downshift - unless the one way clutch isn't working I just don't see how a problem there would cause the behavior I see.

Playing with my leftover parts, it does look like the roller assembly can be put on the wrong way around and it will at least fit together with the gearing. Further, when put on this way it seems to not engage at all going either direction of rotation.

I had parts from 2 different transmissions, and I'm not sure if I did change the spacer or not, I just remember reading that the measurement would affect OD operation if wrong an sweating about getting it right without 100% correct tooling.

My research source is the various manuals on how the system functions and google.

Have fun.

I love this forum. I get schooled every time I log in [coffee] Good luck with your issue.

And the answer is....

Yes, it was backward. Put a new one in (right way around) and it now shifts properly. It's actually quite easy to put in backward, and it not obvious which way it goes, at least not on the one I had. The inner race has a machined groove on both sides that the lip on the sprag assembly fits on. Looking closely it's clear that it's not quite right when backward, but without knowing that and looking closely it's not obvious.

With it on backward it doesn't lock up at all when turned the way it's supposed to lockup, and binds slightly when turned the opposite way. When in OD it would be binding up slightly, but it doesn't really lock up, hence whey OD still worked. I did notice some weird vibration at time in OD, which I attribute to the on and off binding up of the clutch.

All in all a relatively minor thing to mess up, and not a huge pain to fix, but would of course have been better to do it right in the first place...