If it totally locked up (not just temporary nose over) the front servo isn't releasing....could be broken piston/ring.

Put a gauge in the front test port & run it on jack stands.

I had the same problem with a 904 I built .they put it in ,took it out and drove it it was locking up in 3rd .I went to the shop and put a pressure guage on the front servowhen it shifted into 3rd it never released the band I checked the linkage adjustment it was off. I put the unit in 3rd and adjusted the cable so it would go right in the problem was fixed.but you know how it is the trans builder is always at fault lol.hope this helps.

That is what I call 2-3 tie-up, caused by to fast of a band apply or to quick of a front clutch apply. A 5.1 band lever can cause this and so can removing front drum springs. BUT it should free up if you keep driving, if it is truly locking up, the band is not releasing enough at all.

had this happen on mine when I installed the first T-A valve body. Luckily, my car was still on jack stands when I found it. Talked with Paul Forte about it over the phone, and he was convinced I had done something wrong (as was I), but agreed to take a look at the valve body, so I sent it to him. He called me a week later, said he had installed it into his test vehicle and it did the same thing. Locked up in D. He appologized profusely and sent me a new valve body which worked fine. My point is simply that it could be in the valve body (???).

The non lock up valve body is different from the lockup valve body. The lockup valve body uses a boost valve to up the pressure to the converter clutch. Non lockup and lockup input shafts are different as is the reaction shaft. I'm not sure you can swap a lockup valve body and a non lockup valve body.

So your valve body has 3 wires correct? The center wire is 12 volts ignition hot. The forward wire is the O/D solenoid and the rear wire is the lockup solenoid.

Yeah but you were running it with the lockup converter, input and pump. The fluid path is different between the two and it's in the reaction shaft of the pump. The valve body is accordingly different as well. I believe you will need a non lockup single solenoid valve body.

Last year I was running this same set up... 727 pump and input
shaft.. I pulled it out because of a sticky governor

OK, I get what you're saying. It sounded like you just changed all that stuff.

In this case it sounds like there may be a problem in the O/D. I don't have an elements in use chart here, that would help. But if it's locking up in third and not when switching on O/D then I doubt it's the wiring.

Test it in 3rd. I don't think it's possible to get O/D in second.

You have a problem in the O/D then.

Well now we have some more information. I can't answer for the valve body but like TRENDZ says a normal 518 will not allow OD until it's in 3rd gear. Maybe, possibly, the transgo modifications allow this. This could possibly have done some damage, I don't know.

Mike, did you take the OD unit apart when you dealt with the governor valve? I have seen the small bushing between the intermediate and output shafts crack and break into small pieces. This could possibly be jamming the inner race of the over running clutch.

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

Good luck with the double Mike.

I just had a triple at the end of Feb and I feel good as new.

It wasn't nearly the ordeal I imagined it might be.

If you have any questions don't hesitate to PM me.

Kevin

Mr P.,

Is she rolling or skidding??

I was going to ask if you tried swapping wire's around.
Don't know if that is the fix but easy to do .

The direct clutch is disengaged before the overdrive clutch is engaged.