RPM keeps jumping when truck in OD?

[SPR1NK]

my dads truck (93 f350 7.3 E40D hypermax turbo) keeps jumping the rpm up by like a couple hundred rpm or so, only does it when its in overdrive. when he told me about it I thought maybe it just kept shifting out of OD but after driving it myself it isn't shifting, its just jumping up the RPM and then dropping it again for some reason. any ideas why its doing this?

here Is a video of what its doing, kinda hard to hear but you can hear the engine kick up and then drop back down.

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it does it worse at higher speeds too, It was just easier to get the video on a back road at slower speed with less traffic.

 

[tradergem]

Sounds like the torque converter is locking and unlocking, which will cause a drop of a couple hundred rpm when it unlocks. The most common cause of this is dirty or corroded contacts at the wire harness connector on the transmission. If that doesn't fix it then check the connection to the TECA ( Transmission Electronic Control Assembly) on the fire wall behind the driver side wheel well. If the wire harness and connectors are good then check the trouble codes the TECA is putting out for other possible problems.
Good luck.

Jim

 

[SPR1NK]

Alright, we've had trouble in the past with the connector on the transmission, will check those and report back, thank you

 

[SPR1NK]

Ok, cleaned the connector on the passenger side of the transmission and plugged it back in, seems to be working fine now, but both clips on that connector are broken, is there anywhere to buy a new connector for it?

Also put the code reader on it, got these three codes:
dtc 50
dtc 65
dtc 74

 

[FORDF250HDXLT]

https://www.google.com/#q=89-94+e4od+repair+harness

 

[SPR1NK]

Awesome, thank you

 

[icanfixall]

What you see and feel is the torque converter unlocking. As already posted its usually dirty trans connections. ALL the trans harness under the truck going to the back, and both sides should be cleaned and lubed with die electric grease. Use a contact that is harness to plastic. At the drivers side kind of under the master cylinder is a bundle of three connectors that goes to the trans. Clean those also.
After my first rebuild I had a similar issue with converter. Every time I turned on the left blinker the trans unlocked with the flashing. Turns out the bulb filamont broke and fell across the brake like filamont cause the converter to unlock. Same thing happens when we allpy very slight braking but keep our foot in the throttle. In the brake light circuit is a converter unlock message sent to the converter. If that does not happen our engine will stall coming to a stop just like any standard trans rig.

 

[SPR1NK]

If that's the case I wonder if its electrical elsewhere, as a couple weeks ago after he had the hazards on and turned them off and the brake lights wouldn't go off until he wiggled the hazards switch and the blinker switch

 

[79jasper]

Replace the multifunction switch.

Sent from my SAMSUNG-SM-G935A using Tapatalk

 

[SPR1NK]

Multifunction switch?

 

[trackspeeder]

Multifunction switch?

Turn signal switch.