New guy, need advice on differencial

[65 P-30]

Hello all,

Another new guy that is in need of advice. What a surprise right.
I'm starting to think that I may have very well bought a pack of trouble with the purchase of a `65 Chevy / Grumman 1 ton step van. I was expecting a lot of work, but things are getting a little out of hand.
The project now is tracking down the source of the rear end howl. I believe the diff is some type of Eaton, but can be mistaken about this. I haven't found any markings as to just what the diff is. If this is any help in identifying the diff, the entire carrier is removable from the front, and the rear of the housing has a removable access cover as well.

Anyway, I've pulled the back cover for a look around. The good news I guess is no parts fell out when the cover was removed. The bad, going by the amount of RTV sealant on the cover, someone had been there before.
After looking things over, there was no obvious damage, such as broken teeth etc.. However, the insides looked more like the inside of an engine that had missed a few oil changes. The parts were black with what look like a light coat of sludge. The oil that was drained was clean. ( my first thought was it was heat related )
The face of the teeth do not appear to have any abnormal wear patterns and have a dull gray finish.
There is what I feel is a lot of freeplay between the ring and pinion. ( the pinion has no contact with the ring gear when moving the pinion from 12:00 almost to the 2:00 position )
So... any ideas of what kind of trouble I'm in here?
Anything that I should check further, or try to adjust?

I'd like to get by without having to remove the carrier for several reasons, but if it needs to come out, it needs to come out.

Thank you for any and all advise.

[jonzcustomshop]

I think the carrier is relatively easy to remove, just unbolt the ends of the axles, slide them out a bit and then remove the carrier.

I remember my buddy at his garage would put it (the running driving vehicle) up on a lift, run it and then listen to the rear with a stethascope.

[PGSigns]

If the gear has that much backlash that it your noise. Good news is they are easy to get out bad news is you may want to try and find another pumpkin. You can rest up the gear but once they are worn and get noisey they stay that way. Check the width on it, a dana 60 may go right in it with out a tone of work.
Jimmy

[Big Fenders]

The pinon has no contact with the ring gear between 12 and 2 'oclock positions......That measurment is called backlash. I just installed 3:08 gears in my 1963 chevy truck and that measurment had to be about 8 THOUSANDS. So your rear end needs some serious attention. What adjusted pinon to ring gear back lash was the shim or shims between the pressed on pinon bearing. Your probably is similar to mine. A shop manual would be a big help.
Bob

[padresag]

they do see wear after all these years . you can more than likely just rebrg it and it will last you.
these things(rear axles and trans) were also not likely to be the quietest of things to start with and deep lug tires will enhance it. remember that you are inside of a large metal box that will intensify any sound, so that it may seem noisier than it actually is. those walkin vans are not really quiet like a Cadillac.
ron

[65 P-30]

Well...first off, thank you for all of the replies.
I went a head and pulled the carrier out, and it wasn't a pretty sight. The pinion gear is toast. The ring gear isn't bad, but of course they need to be replaced as a set. The teeth on the pinion are worn way down, at the bottom of the gear, the point closest to the hub. The top of the gear isn't nearly as badly worn.
I'm not sure if this was caused by normal ware and tare, or misalignment of the gear set.

I just can't see dumping 1000~1500 into the diff. The truck needs an engine, and suspension work as well. It just might be more work than its worth to get this truck back on the road as a work truck. As it is now, it just needs to be moved around the yard, so the shot diff will have to do for now. So...I'll slap it back together the best that I can, and take a wait and see approach on finding a replacement.
Is there anyway of changing the point that the gears mesh to the center of the tooth to remove the load on the worn part of the pinion?

Please tell me about what newer Dana may fit under the old dog. I thought that GM had a pretty major change in the width of the axles , or the spring mount positioning around `73 and then again in what `89 ? I'd really like a newer running gear, but I haven't the equipment for changing mounts and such. So I think that I'm kind of stuck with what, pre `73 axles as far as bolting an axle in?


Well thanks again for all the helpful tips, and if anyone happens across a good carrier, I have a home for it. ( wow, I wonder how much the freight would be on that puppy )

An update, I've located a diff from a `65 3/4 Chevy pickup. It's a model without the removable carrier. The u-joint is the same, but I can't tell if the spring mounts are the same, and if they are in the same position. Anyone know if this diff would be a direct fit into the P-30?

[Captainfab]

If that '65 3/4 ton rear end is different than the one in your P30 it is quite likely a Dana 60. I don't know if the spring spacing would be the same between the '65 3/4 ton and your P30, but I would say there is a good chance it is. Either way that Dana 60 would be a much better choice than the HO52 you have. You can still get anything you need for a Dana 60 and less $$ than for the Eaton HO52. Here is what the rear cover on a Dana 60 looks like. There will also be the number 60 cast into the web to the lower right or left of the rear cover.

[jonzcustomshop]

if they are both leaf spring frames it will probably bolt right in, bring a tape measure to be sure. I had thought that the p 30's used a regular truck frame, basically sold as a cowl/chassis, and then a coach built -grumman in your case- body was installed.

[65 P-30]

Thank you,

As much as I can tell, the body is the only thing from Grumman. The frame, engine, axles etc. are a light GM truck. As to whether or not the frame is the same width as a frame used in a pickup, I can't say.

As best I could measure with the diff still installed in the van, it looks like there could be a slight difference in the spring mount spacing, and the over width from backing plate to backing plate. Again, this is with the axle installed, and bending a measureing tape over this and that is not a very accurate way of measuring. On top of that, the backing plates aren't the same, so one backing plate may have a different off set.
And, did the '65 3/4 have coil or leaf springs in the rear?

I'm not being picky here, but how close would the gearing be from a 3/4 pickup diff to a 1 ton step van? As it is, the van is turning about a half a million rpm @ 35mph! A drop in rpm will be welcomed, but it maybe a problem if it drops to much, if ya know what I mean.

More to follow as it develops.

Thanks again for all the help and ideas.