rickpilgrim

We have a 1993 K3500 X cab dually that WAS a 6.5TD but now is powered with a mild 1972 427 Truck engine and a GM goodwrench reman trans for the 6.5 TD with 8200 mi on the trans/engine. I scrapped the stock PCM and shift the trans with an optishift controller. I had to update the A&B solinoids to 98 up ones to run the optishift, they came from Advance auto parts
We drove it home working perfectly and the next morning we had no reverse/4th and delayed to max rpm/mph shift to 3rd. I mounted the optishift were I can see it and when driving it displays the:

Engine rpm-matches the tach perfectly
vehicle speed-matches the spedo even though its seperate from optishift
throttle position-varies from .83v to 4.89v like it should
gear selected and soliniod actuated-same as current program installed
torque converter lock up status- works good
trans temp- within 10 degrees of aftermarket gauge mounted in cooler line
line/pump pressure- set at 85% of safe max and stays steady

The fluid is as pink as the day we installed it, the filter is clean, there was no debris in the pan and the solinoids check OK and the wiring from optishift to inside the case has good connection.
Anyone have any ideas what I have missed that would cause this?

Allan In NE

I usually don't get involved in these cross-bred systems, but maybe can help point ya in the right direction somewhat.

Does the truck have engine braking in manual first?

Disconnect the electrical connector to see if you then have reverse.

There is an old saying that 'if an electrical part is going to fail, it will do it within the first 20 minutes of operation.'

Your symptoms are pointing at the direct clutch area, but with a brand-x controller, I really can't help you all that much.

Allan

rickpilgrim

Had some time today for testing and found out that:

No engine braking in manual M1/M2 or M3 (M followed by the gear # is what the Optishift shows when not in OD position)
Un hooking the plug at the trans had no effect on reverse, but did set a trouble code in the Optishift.
My TC is 8 months old and not made anymore, but the similiar lower priced variant still is available. Here is the link for it

The US Shift Transmission Control System

Allan In NE

Ouch,

This just does not sound good.

At this point I would rule out an electrical issue.

Watch that line pressure at moderate throttle when it shifts to 3rd and then also as it attempts 4th. Look for a 2-4 lb or greater pressure drop.

If so, you've found your problem. To me, your issue is screaming blown seal, broken piston, etc.

Allan

RacerX

I dont know. I think it is electrical. These trannys are almost indestructible so I dont think it would be a piston or seal. I think those A&B solenoids you got from Autozone maybe the culprit. I m not sure if your Optishift can test them but I suspect one of them is either fully energized or not energized for the 3-4 upshift or for reverse. I think for this trans to get into reverse the Manual Low band has to be held while the Forward Clutch is active. Should be different band for OD but may be the same solenoid?