Transmition problems

[targetman]

I have a '91 E-350 with the diesel motor. Last week the trans. started slipping while in drive. I changed the filter and put in some additive. Stared running better for a few days. Yesterday while driving down a highway it started acting up again. Slipping real bad and the OD button was blinking. What should I do? I know it's going to be a costly repair.

[ModMech]

Most likely the TPS is either bad or misadjusted, that would cause this.

[targetman]

Thanks ModMech, What is the TPS?

[ModMech]

Throttle position sensor. It is located on the driver's side of the injection pump, and is accessable from the front with the air inlet bellows removed.