Ok so I'm still getting the bugs worked out of my 505 based 440.

Finally running great so I took it out cruising yesterday. While driving on the highway for approx. 10 minutes, I heard a faint grinding noise, so I slowed down a bit. Then I heard it a few more times. I shifted to neutral and pulled over and shut it off. I then restarted it and I could only get it into first without grinding. I was close to the exit so I idled it off and into a parking lot. Nothing out of the ordinary underneath.
With the car off I manually shifted thru all gears including reverse.When I restarted the car, everything worked great and I drove it home as normal on the backroads.

Any ideas as to what's going on here? I'm not sure if it was trying to engage another gear while driving or what

Check your fluid level. Low fluid will cause all kinds of noises. Check your shifter alignment. Whatever is wrong, doesn't mean the trans is toast. Fully rebuildable through Passon, Brewers and others.

I checked the fluid this morning it's full, is it possible that it was trying to get in 2 gears at the same time?

That is possible, but the grinding noise has me concerned. A wild guess may be a main shaft bearing may be going.

thanks, I'm gonna go try it ut again and see if it was a fluke

I would drain the fluid out of it through a cloth into a clean container and then run a small magnet through the cloth and old lube and go from there All transmissions , manuals and automatics make some metal, don't be overly alarmed with small particles, worry only about the big stuff

Thanks I'll try that

4-speed lower plugs are magnetic. Aluminum cases have a big magnet glued in them.

Grinding ??? Maybe reverse isn't moving back far enough.

Before I did anything messy like draining it I'd be checking the linkage alignment

Clutch/release bearing?

Kevin

My though as well. If it won't go easily into gear perhaps the clutch isn't getting it's .060 clearance when the petal is depressed.

All the pre 1971 NP833 I've work on didn't have magnets on the drain plugs, we would JB weld them on the first time we had the drain plugs out. I've worked on three NP833 O.D. trannys recently and they all had that big flat round magnet your talking about I removed one from one that had a hole in the case from hitting something, I'll glue it back in there now that the case is welded up thanks for the update on why it was in there to start with

tht's just it, it drives fine, goes into gear easily, but a few minutes after driving it aggressively it starts the noise, and I have to come to a stop, then it's fine again. I discovered this last night after taking it out for a drive again.

Is it making the grinding noise when changing gears or when you are driving down the road and not changing gears ?

it's making the loud noise while in 4th gear cruising down the highway NOT shifting gears. I'm baffled and dreading pulling the trans.
Things rolling thru my head: mainshaft bearing/ throwout bearing/main cluster gear.
Has anyone had this happen?

Put up on lift and try again. U-joints good?

If you have a cluster assembly end washer wearing out the cluster gears will start to off mesh with the main shaft . If it is really worn the cluster will move back and forth a lot causing grinding noise.

Years ago mine was making a racket and it was the input shaft bearing. to the previous post ... I've never seen thrust washers wear to that degree.

I haven't either, but there's a video on YOU TUBE showing one that has. Or someone left it out upon assembly.

I had one in my 69 Bee that sounded like it was full of rocks running down the road, rear bearing was the problem.

It made so much noise I could hardly hear a thing , once I rebuilt it I could hear the wiring under the dash shaking while the car was moving ...

only if your shifter is grossly out of adjustment , but then you would have a very hard time changing gears and that doesn't sound like the case.

Has the trans been rebuilt ??? Cluster pin replaced , especially if it was run before with ATF ???