The Stovebolt Site Forums The Shop Area Engine Shop 3600 Pinion Play

Hey guys, I'm sure I know the answer to this already, rebuild or upgrade, but here goes: My '49 3600 has the original HO72 4.57 rear. Tried to get it safetied and the mechanic said the drive shaft was worn, too much play. I removed the shaft and found I have about 1/8 to 1/4 inch of left-right play in the pinion. I don't hear any driveline noise and everything runs smoothly. There are no leaks on the front of the housing (the rear cover is another matter).

How much play should there be and can I tighten this up without tearing the whole thing down? Thanks everyone.

That much play when you are turning the pinion flange is normal. If you hold the pinion from turning & have play up & down it is a worn pinion brg. It can be replaced by pulling the 5 bolts in the flange & pulling the assembly out the front. It has a massive brg. that is double row ball brgs. The replacement is a taper roller brg. assem. It is expensive. The flange uses a cork gasket that compresses according to the shims. The pinion nut takes a big socket & preferably a stout air impact. What does pinion play have to do with safety inspection?

are you talking rotation free play or side to side,,if it is rotation you are fine if side play you have a problem...doc

Yeah, it's side-to-side. I took the truck to a reputable shop for the pre-registration inspection required here in Alberta. Probably could have found someone who would just sign it off, but I'm going to carry my wife and daughter in my truck so I appreciate knowing all that is wrong with it.

Well, I guess finding a later model carrier and getting a 3.90 set from Randy's is in my future...

Hate to give you bad news dude, but sounds like if you have 1/4" side to side movement in the yoke you're pinion bearing is missing, or to put it another way, completely ground up. No wonder the safety lane grounded it. At this point I would think that the rear end housing is filled with metal and it would require a complete tear down and very, very thorough cleaning of the housing before reinstalling anything. Including the hubs, just incase the chips chewed up the seal and got into the wheel bearings. Chances are 99.9% that the rest of the bearings and gears are shot by now.
I would find that new pumpkin and spend a weekend cleaning out and flushing the housing. I bought one like this about 20 years ago and went through the same thing. The guy I bought it from told me that he just put in a new pumpkin. Only problem was he didn’t bother cleaning out the housing and the “new gear” was shot now also. After cleaning and putting in yet another new gear, I drove it for 50,000 miles before I sold it.

Who is “Randy’s” and where ya gonna find a 3.90 gear for a 3/4 ton? You mention that it is a 3600 yet you’re profile says 49 GMC, are the rear ends the same for both of them or is that 3.90 gear specific to the GMC? I sure would like to find a supplier for a 3.90 that would fit my 1950, 3600!
Denny Graham
Sandwich, IL

Denny,
randy refers to "Randy's Ring and Pinion". He has a web site and there is a listing for a 390 gear set which he may be carrying again.

http://www.ring-pinion.com/

It only fits the carriers from 67 to 72 but the whole unit interchanges from 1948 to 1972. Therefore to upgrade, say a 1949, one would use the pumpkin from a 1967 to 72 and install the new gearset in it.

Now, I don't understand how a pinion with 1/4" play from side to side doesn't leak.

Always looks worse to the owner, I guess. 1/4 inch is not an xact measurement, but the play is significant. The bearing is probably shot. Strange, though, I changed the rear cover gasket to stop a leak (unsuccessfully), but no metal came out with the old oil. I've also changed a rear wheel bearing and seal, with no evidence of ground metal.

The next step is definitely dropping the pumpkin and cleaning the housing. I'll take the center to a driveline place and get it checked, or find a later carrier and get new gears put in all at once.

So much for "on the road sooner, rather than later."

Highflyer

I to am trying to get 3.90 gears to go faster. I will try calling randy. Thanks for the info.

My other ride KingAir 350, Happy Trails

Hey all,

Don't mean to hi-jack this thread, but I'm not sure they are making the 3.90 gear set for this axle any more. If they are, somebody PLEASE respond and let the rest of us know so we can "speed up" our rear ends as well.

Just a note: the H072 was in the 3800 (1 tons) and the H052 was in the 3600 (3/4 tons). Only difference is the pumpkin! Everything else is the same. Though the H072 is rated for 7200 lbs and the H052 is rated for 5200 lbs.

Highflyer,
I would really like to see a photo of your frog eyed Sprite. I remember a buddy having one when I was a teenager and man was it ever cool!

Fred

jhaa,
I am pretty sure that they are still making the 4.10 gear set. The drop down to 3.90 is only a 5 % change.

try tightening the pinion nut have seen some work loose and it won,t cost much to try,,if loose remove clean locktite and tighten to 100lbs...doc

Thanks Doc, I'll try that. Won't make it cost any more to fix later.

Randy's shows the 4.10 and the 3.90 on their site, but I did search for HO72, not HO52. Better check my part numbers again....

Truckernix.. It would be more of a collage than a photo.... The Sprite is spread out more than the truck.... I thought a smaller vehicle would be easier to start on... NOT!

dgallagher: Used to refuel a 350 in Peterborough, Ont. It came in from Detroit all the time... Shamrock on the tail. Beautiful aircraft.

Book marked that Randy’s Fred, I’m still tryin to get all this scattered info together on the rear ends that will interchange with my ’50, 3600. Anyone know just what you have to do to the drive shaft if you put the later pumpkin in the older AD’s, like change the length, change the yoke?
Dan, I think you‘d look real sharp if you’re other ride was a Pitts, just so happens I got one lookin’ for a home!
Denny Graham
Sandwich, IL

Highflyer, I have a '54 and in that pumpkin, there IS a lash adjustment. I believe that you have to drop the pumpkin to do the adjustment but I was able to take up the freeplay when I bought my 4.10. I have the old 4.57 which you'd be welcome to. However I think shipping cost would kill you. It weighs about 105 lbs.

Denny,
you don't have to change anything on the yoke or driveshaft as it bolts right up. I measured the distance from the yoke seat to the housing parting line on mine and between the old and the new there is a difference of 1/4". I have a splined slip joint at the back so this won't be a problem.

The reason that they state that the new gearset only fits into the 67 to 72 pumpkin has to do with internal differences.

In case it may be of interest, the torque specification for the flange nut is 160 to 280 ft lbs. In addition it takes a cotter pin.

Yep, Fred is correct there, and try and get 280 ft.lbs. of torque on that sucker while your laying on a creeper under the jack stands!!!

That is though, probably the most important torque specification on the vehicle followed by the head bolts because we are affecting the bearing clearance ever so slightly.
I tightened mine as tight as I could get it then took it to a friends garage who had a lift. Then you can get 280 ft.lbs. of twist on it!

Denny Graham
Sandwich, IL