NP271 jumping out of 4LO

motorwood

motorwood

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Joined
Jun 16, 2010
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318
Anybody experience a NP271 wanting to jump out of 4LO while pulling?
 
In to watch this. Have a buddy with his jumping out of 2hi intermittently after a hard pull.
 
wore out pads on the shift forks and/or bent/pulled snap/lock rings on main shaft. happens alot with truck that use 4x4 alot or are over 100k.
 
It's a ford case, with a drive flange output, running upside down in my first gen. My slip joint in the driveshaft is very stiff, sometimes grinding when hitting a hard bump. Could this have messed up the snap rings? This has been pulling for 4 seasons, 2 of which were at 900-1000hp.
 
Check the synchros in it. If it still has synchros, they could be worn. Just a thought..
 
Or the shifter needs to be adjusted. Maybe it was never truly in
 
Shifter is good, strong detent. When suspension compresses, the whole output shaft flange and all is moving in and out. (Remember it's Ford with a bolted output flange)
 
Id check the snap rings maybe? I know if that shaft moves even a little bit, it'll cause weird stuff to happen in there.
 
Make sure your driveshaft isn't too long. Are you running traction bars and/or suspension stops?
 
Jed, I wasn't running my stops last pull, and I think the drive shaft my have pushed hard into the output, probably popped the snap rings. I'll pull it apart today snd report back. I don't think the drive shaft can telescope properly under the huge torque load of s sled pull. Plus the original application uses a hanger bearing, with the slip joint between the hanger and differential, putting no thrust load on the transfer case. Mine is s 1 piece driveshaft in s regular cab.
 
Easy fix !! I had driveline issues when I ran rear blocks without traction bars. I had my 271 built with the Ford output flange. I'm still running hanger bearing on ECLB truck. The slip joint is between hanger bearing and rear axle.
 
Welded the fork up, ground it down, ran it with suspension stops, worked fine.
 
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