1999 ford 7.3 help

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Sep 20, 2025 | 04:17 PM

Landan

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1999 ford 7.3 help

Hello I have had my 1999 f250 7.3 for around a year now. I recently had a pretty big issue, I was driving down a road in my town and saw some people so had to let them hear the 7.3 and heard a noticeably loud clank noise, then abruptly lost all gears( no reverse, no forwards gears). Got it towed home and fluid is super clean, changed torque converter and flex plate, still nothing messed with fuses and put a new trans filter in it. I’m at a loss for what it might be maybe you guys could give me some ideas? The trans still has pressure and it’s the 4r100.
Thanks Landan

Sep 20, 2025 | 05:32 PM

lshort

Laughing Gas

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From: Newton Illinois

Is it 4WD? Could be the transfer case chain possibly. jack it up and see if you can turn the rear driveshaft

Sep 20, 2025 | 07:24 PM

Landan

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I jacked up the back and only the passenger side spins the drivers may not spin because the truck had been sitting for 3 months but I don’t know for sure.

Sep 20, 2025 | 07:39 PM

Mark Kovalsky

Frmr Ford Trans Engr

Joined: Aug 1999

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From: SE Florida

Was the transmission in park? Were you spinning the driveshaft with the transmission in park? Is the truck a 4x4?

Sep 20, 2025 | 08:46 PM

Landan

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The truck is a 4/4 and it was in neutral when I tried spinning it

Sep 21, 2025 | 08:22 AM

Mark Kovalsky

Frmr Ford Trans Engr

Joined: Aug 1999

Posts: 24,717

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From: SE Florida

Put the transfer case in 4x2 and the transmission in park. See if you can spin the driveshaft with both rear wheels off of the ground.

If the driveshaft won't spin, the transfer case is good. If it does spin when the trans is in park and the transfer case is in 4x2, the transfer case has failed.

Sep 21, 2025 | 01:11 PM

Landan

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I jacked it up and it’s in 4x2 and In park and dosnt spin. So I think that means transfer case is good. Any other ideas? I’m pretty lost on what to do now. I think next step is buy a new transmission.

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Sep 21, 2025 | 01:42 PM

Landan

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I just would figure there would be metal in the pan or something. Any transmission you recommend lol

Sep 21, 2025 | 01:51 PM

#10

Mark Kovalsky

Frmr Ford Trans Engr

Joined: Aug 1999

Posts: 24,717

Likes: 2,642

From: SE Florida

I recommend a 4R100 4x4 from a 7.3L truck. Also, you need to know if it is a late '99 or an early '99. They are NOT interchangeable.

The late '99 has a speed sensor on top of the trans, just behind the bellhousing. The early '99 does not have that sensor. Make sure you get the right one or it won't work right.