How did you get a 518 to lock up? My first gen Cummins had a well built 518, I would have loved a lock up switch

How did you get a 518 to lock up? My first gen Cummins had a well built 518, I would have loved a lock up switch

Pat, I had the same thought path as you did (I was the one who built this trans for Mike).

If the OD roller was seized it would absolutely act like this.

You sound like a man who speaks from experience that the spring and roller in the OD can be backwards (upside down). However I'm not sure how that's possible, or if it would even act like this if you did?

The spring cage is made in such a way that the top lip (when assembled correctly) can not pass through the outer race. If you try to put it in upside down then the cage won't assemble. This was a brand new roller/cage assembly. Also, if the springs were forcing the rollers away from the ramps, then I believe the roller clutch would never lock up regardless of direction. The rollers would always be held off the ramps no matter which way the roller was spun?

The other thing that doesn't make sense is that Mike had this trans working in 1st and 2nd last year with the OD turned on (Manual switch). He says it would actually over drive in 1st and 2nd. This is against what normal valve bodies would do, but I have no idea what the trans go kit allows?

Now the OD switch does not cause any issues in 1st/2nd... only direct. If the roller was in backwards/upside down, and could cause an issue as you described it should do it in 1st and 2nd too... not just 3rd. This also would eliminate the clutch stackup height being wrong causing the issue. UNLESS Mike was mistaken last year and the OD never actually was doing anything in 1st or 2nd.

In that case it would open back up all of the OD issues (tight clutch or roller clutch).

I don't see how the clutch clearance could do it though. You're literally turning the OD direct clutches off when the piston is applied. If the piston moves far enough to apply the OD clutches, is it even possible that the direct clutches could still be on? I could see if the direct clutches were screwed up in that they had an extra clutch in them or something, that the stack might be so tight the OD piston could not move at all. But in that case this limited movement wouldn't allow the OD clutches to apply anyway?

I told Mike to take the car out tomorrow and drive it in manual second. With some speed up flip the OD switch and see if it actually "shifts". If it does... the OD unit would seem to be functioning correctly and would lead me to a valvebody (Check ball?) or wiring issue somehow causing the reverse/low band to apply.

The other thing Mike and I talked about tonight was the wiring. The connector was lost this winter and the trans was re-wired. With this rebuilt manual valve body/transgo kit that's in this thing, I have no idea what would happen if you turned the lock up circuit on. Looking at the valve body flow diagrams it doesn't appear that fluid could get from the LU circuit into the low band anyway, but who knows with the trans go kit that's in there I suppose.

Any/all help is welcome...

I'm thing about picking up
another trans.. one of the NON lock up OD units.. what was the years
and trucks that this trans came in... thanks

89-93 518 was nonlock-up

Only if it was behind a diesel. The gas engines were lockups. But there were exceptions. I believe it could have been ordered either way or a GVWR was the deciding factor. In either case just finding a certain year isn't a determining factor. The only way to go by the year is if it was a diesel, which would be 91.5-93 intercooled models.

I will assume that even a diesel unit would work with a governor
change and maybe changing the valve body to get the shift points
up

Well, are you going to spill the beans on what the major malfunction is/was?

Had a 20min break today between family stuff. Got everything all apart. Sure enough the OD roller clutch was installed backwards. There is indeed a lip on the roller cage to prevent it from being put on wrong... BUT if you load it from the front, instead of the rear (like it's supposed to be) it will go on backwards.

The good thing is everything in the trans looks brand new still. Flipped it over, and got it just about all back together. Just need to install the OD unit back onto the trans. Should be back together right after work Monday Mike.

Tomorrow is my wedding anniversary... My wife would kill me if I tried putting it back together tomorrow... Lol