'93 D250 Cummins truck.
I've rebuilt the trans with:

-5 pinion planetary and corspondiing intermediate shaft,
-new steels+ clutches
-billet apply lever and servos ECT.
-TFOD-Hd2 valve body

Truck is in OD by 35mph. Rushes the 2-3 shift and won't hold second gear when "2" is selected. Going from "2" to "D" engages the OD. 1-2 shift feels good. Holds first gear pretty well depending on were I put the TV cable. Sometimes downshifts after I've come to a stop.

I was pushing my limited skill level rebuilding this thing. I'm flumuxed. Need some ideas of what to check. I'm working on getting a pressure gauge for the pressure ports to make sure I'm in the ballpark on that. Any help would be greatly appreciated.

Well, a couple things, O/D at 35 is normal under light acceleration. 2/3 shift on my truck happens before 25 under light throttle. You didn't say how you were accelerating or give any specific MPH numbers at what throttle opening.

One thing that did catch my eye was the statement "sometimes downshifts after stopping". This is almost always a sticking governor valve. They are very sensitive about this. These valves must be absolutely free. The aluminum valves tend to mushroom over. You can replace them with steel valves but you must use the diesel specific pieces. The trans up shifts at WOT are controlled by the governor. Gas calibrations are way to high for the diesels low RPM operating range.

That's some genuine help right there!! I'll look online for a steel diesel gov valve. Edit: I'm pretty sure I replaced that with the one in a Transgo TFOD-HD-2. It's been a year so I could be wrong.

The early shifts are when I'm on light throttle. Didn't realize it was that good at upshifting. When the trans is cold a light throttle the 2-3 upshift is well spaced. After it gets warm it seems to go 1-3 but not cleanly. When I give it full throttle 1-2 seems good but the 2-3 shift happens earlier than the 1-2. This is by ear as I don't have a tach yet.

The trans is not downshifting to first gear when stopped consistently. It bound up today at a stoplight for half a second when I went to leave with a light throttle input. Usually I can feel it clunk down to first at about 5 mph.

It rarely downshifts on its own. A hard roll on at 50mph won't produce a downshift. I'll check it at lower speeds.

I do find it weird that it won't hold 2nd gear when 2 is selected on the column.

Most everything you described sounds pretty normal for a diesel except the not downshifting. There are two valves in the governor that will mushroom, the inner spring loaded valve and the free weight on the other side.

I have fought this on my trans but mine ended up being the front servo hanging up on the 5.0 lever. I put mrrandyj's billet front servo and a 4.4 lever in and that has seemed to cure mine. It only did it when it was good and hot though. I need to wait until the temps reach back into the 90's here to be sure.

Forgot to add, you might try adding a little more throttle pressure with the cable adjustment. Flip the lock lever up and slide the cable rearward about 1/4 inch and see what that does.

I'll try messing with it again. Btw a '93 kickdown cable moves different than other years me thinks.

I barely drove the truck before tearing it all apart so I'm not completely sure what normal is. I still think it's working funny.

Depends on what you call different from what. It pushes the TP lever. Magnum gas engines pull it but regular LA linkage also pushes it. I have a 92 1st Gen so I'm fairly familiar. Mine has been converted to a lock up converter.

Bought a cheap trans pressure tester. $28 on amazon. Total Garbage. Gauge needle jammed when it went to 125psi (on 300psi gauge). Found another gauge I was able to adapt it to my needs. Redid the tests and got the following:


I’m getting the following pressures
--------------------------------Front Servo-----Rear Servo--------Acum. Port
Throttle valve--------------Front---Rear----Front----Rear----Front----Rear
Manual 1st gear-----------0---------0---------75-------110------75--------110
Manual 2nd gear-----------0---------0---------0---------0--------75---------105
Drive-------------------------90--------125------0--------0---------90--------125
Reverse ---------------------20--------20---------------------------------------------
Neutral---------------------- 75--------75---------------------------------------------

The gov pressure is running about 1.7-1.9 x the MPH or about 60 psi @ 30mph with the throttle valve off (front) didn’t test it with it forward. This is double what the FSM recommends but maybe the transgo kit changes that?

Before I drop the pan and change out what is probably a mushroomed piston (thanks Guitar Jones!) I was hoping I might narrow down some other possible problems. Like I said earlier, it is rushing 2nd gear and going to 3rd real quick and doesn’t like downshifting. Shifts are pretty soft also. I didn’t drill out the shift hardness hole much on the transgo kit to help ease the shock loads on the driveline, but I didn’t think it would be this soft.

Those governor pressure numbers are exactly the same as my truck. The diesel is different than the gas engines.

Adjust the kick down cable.

coasting 15-20 mph throw it up into park momentarily.... the park rod ratchets on the park pawl and can loosen a stuck governor.

I wouldn't suggest doing this. 1st, it isn't going to do anything for a mushroomed valve. 2nd it could cause much damage and D or whatever number we are on, I've never seen it fix anything. YMMV, don't try this at home kids!

Tried that before I asked here. Now it doesn't like downshifting.



It's maxed out. I've played with it extensively.

Only thing I've noticed that I haven't mentioned is sometimes when I start the truck and quickly put it in gear it doesn't do the normal thunk as it takes up driveline slack. It does a softer version but after a min or so if I shift out of park/neutral it does thunk hard. Ive checked fluid levels and they look good so I dunno.

I've read that the 46rh can be converted be able to lock a tq converter and my current Georend converter can be upgraded to a locking unit. Before I get into that Im probably going to drop the valve body and replace the governor valve like Jones recommends. Maybe and drill out the shift firmness hole a little more and put a new filter in it. If and when it breaks when I try out my new turbo and ppump then I'll try converting it.

if the park deal changed the downshift aspect, I'd say you are correct that it's time to pull the gov assy and take a good look. Starting the truck and immediately throwing it in gear can have the affect... probably fluid fill absorbing some of the "hit".

I don't follow you on the 46 lock up deal.... they have lock up converters.

...and I'm quite certain that Guitar was referring to the gov assy, not a valve in the valve body.

The 91.5 to 93 diesel 518/46RH was non lock up. You can convert them but it's not a simple bolt together deal. The lock up converter is thicker than the non lock up so you will need the 2nd gen diesel engine to trans adapter plate and starter. You may have to modify the frame rail to get the starter to fit. In addition the cross member has to be moved back 1.125 inches as well as shortening the driveshaft. Shift linkage and cooler lines also must move the same amount.

Here is a link to my thread on converting the trans to a lockup.

Lock up conversion thread

thanks GJ.... thought all "RH" designated trans were lockup. Knew the 518 had some non.