Sm465 knocking while in reverse

Jarrett Melvin

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Almost finished swapping my c30 from 2wd to 4wd and I've come to get a knocking in my gearbox while in reverse.

I swapped the old 2wd 465 for a 4wd one. New pilot bushing. Changed the clutch. Got a 208 t-case and got a new one piece drive shaft. All I know it has is a 14 bolt rear end. No front drive shaft yet.

Any forward gears truck runs fine feels fine shifts fine.

Shift Into reverse and let out the clutch and you can hear a clicking/knocking and can feel in the shifter. It increases with rpm and speed as well. Clutch in or out, you can still here it. Don't hear nothing while going backwards in neutral.

The gear box come from a running truck, the t-case was salvaged. Brand new drive shaft and u joints.

One thing I notice because I have no bed on is my rear end tips up when I try to accelerate in either direction.

New fluids in everything.

Stumped as to what it could be or of it's worth worrying about
 

Jarrett Melvin

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I tried to upload a video of it but it won't let me. It seems when u reverse fast. It don't knock with foot on the throttle but when u let off it knocks.
 

78C10BigTen

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If your rear tips up (depending on how far) id say to check your u bolts for tightness and not broken and that your leaf sping center bolts are properly seated in the perch.
 

Jarrett Melvin

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If your rear tips up (depending on how far) id say to check your u bolts for tightness and not broken and that your leaf sping center bolts are properly seated in the perch.

The centers are seated. I made sure of that when I installed new springs. Would the tip of the drive shaft cause a knock like that you think?
 

Jarrett Melvin

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It possibly could be u joints...

There brand new and no miles on the expect a bit of yard driving. I can't move the drive shaft at all. No play in it or nothing.

Only thing I haven't checked besides u bolts was my transmission Mount
 

78C10BigTen

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There brand new and no miles on the expect a bit of yard driving. I can't move the drive shaft at all. No play in it or nothing.

Only thing I haven't checked besides u bolts was my transmission Mount
I think in this case id attatch the front shaft, remove the rear shaft, put it in 4wd and go in reverse to see if its in the rear end or Tcase. Im not much help as my square is 2wd but im thinking, and tossin out what i can think of.
Side note: id check the tranny mount too, see if theres any slop.
 

Big Chip

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Did you install a new flywheel?
 

Jarrett Melvin

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Driveshaft/pinion angle?

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Oof, mine is set close to the bottom one. But there's a wedge under my leafs. That set the angle when I installed new ones. But because I got a long one piece shaft it's not as steep an angle for the long shaft opposed to the shorter 2 piece shaft
 

Turbo4whl

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You could have a bad bearing on the reverse idler gear in the trans. I would also try what Ted @78C10BigTen suggested. If the noise sounds the same driving backwards with just the front axle in place the trans may be the issue.
 

Turbo4whl

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Oof, mine is set close to the bottom one. But there's a wedge under my leafs. That set the angle when I installed new ones. But because I got a long one piece shaft it's not as steep an angle for the long shaft opposed to the shorter 2 piece shaft

That is not good as @Snoots stated.

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Jarrett Melvin

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That is not good as @Snoots stated.

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I checked it again this morning. It's not as bad an angle as I thought but the pinion is still slightly tipped up more then the shaft.

I do think the problem is in the trans.

But it only seems to happen in reverse, with foot off the gas. When doors on the gas it don't knock or click until u let off. But increases frequency with speed
 

AuroraGirl

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I don’t want to brag or anything but mine does make a knocking noise and a whining noise in reverse if the conditions are correct.

Pinoonangle short driveshaft(because the cross member ain’t in the right spot or direction, the t case mount is broken, and the motor mounts are twisted a bit. One leaf is broken, and the u joints are surprisingly okay, but if I go reverse and it’s gonna move a lot on the mounts, it will inock. If it doesnt, it will just go WEEEEEEEEEE in a speed dependent high pitch, something.

Go look under your bed by the front, any Dents? I can tell line has kissed it once I awhile you marvel at the homemade driveshaft notch
 

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