I went and pulled off the hitch for my truck today at my local yard. While there I noticed an older early 60's dodge truck so for fun I jacked the back end up as I wanted to see if it was a posi unit. So i turned the right wheel (truck had no driveshaft) and the pinion turned but the left wheel didn't budge so I turned the left wheel and the pinion turned but the right one did not move.
The axle looked to be an 8 3/8 or 8 3/4 type with no back cover and the carrier removes from the front. It was a 4.5" spacing 5 bolt axle with right hand thread studs on the drivers side and left hand threads on the other. So is this axle busted or is it a strange type of posi unit. I didn't turn the pinion itself as I didn't want to crawl under the truck. I thought if it was a posi both wheels should turn the same direction and a regular diff should turn opposite directions.
Anybody come across this before?
DiverDwnPowrRam
03-06-2009, 05:09 PM
my 73 had that axle 8 3/8 front carrier removable. It is sure grip...great for the street but sucks the stink out of bherders socks in the woods...just an opinion.
cribbs74
03-06-2009, 05:20 PM
Thanks Diver, I'll admit I don't know a whole lot about axle operation but, I thought with any type of limited slip/posi that both wheels would turn in the same direction if you had both up in the air and turned one side.
This isn't a big deal I am just trying to gain some knowledge.
B-300
03-06-2009, 11:59 PM
It's either a limited-slip or it has welded or broken side gears.
The 8-3/4" differential removes from the front after removing the axles. Early models have 2 piece axles that have a large nut holding the flange to the axle. (The 8-3/8" has a cover on the rear.)
3834B
03-07-2009, 08:03 AM
Sure sounds like an 8 3/4 Sure Grip to me. They are a good axle by most accounts. Likely a 3.91 gear. If it has (489) cast on the case then that is a good one.
cribbs74
03-07-2009, 09:14 AM
It's either a limited-slip or it has welded or broken side gears.
The 8-3/4" differential removes from the front after removing the axles. Early models have 2 piece axles that have a large nut holding the flange to the axle. (The 8-3/8" has a cover on the rear.)
Yep it had Big nuts on the end holding the flange and like I said right hand studs on one side left on the other. Thanks for the info. Is it worth my time messing with it? I have a 9.25 right now which I'm sure is stronger but it's a peg legger. Thanks for the info
cribbs74
03-07-2009, 09:15 AM
Sure sounds like an 8 3/4 Sure Grip to me. They are a good axle by most accounts. Likely a 3.91 gear. If it has (489) cast on the case then that is a good one.
Where should I look for the "489"
3834B
03-07-2009, 09:38 AM
It will be on the third member on the driver side. Likely a six digit number and you will just pay attention to the last three digits of the number.
http://members.tripod.com/~Mojo_Page/chry875.htm
DiverDwnPowrRam
03-07-2009, 09:39 AM
typo on my part I meant 8.75. I remember that no one wanted to work on two things on my 73....front end alignment and rear axle bearings. I remember the axle being collected for street apps but as i needed something for hunting and fishing I could not use it. Get stuck and one wheel spins and the other just sits there.
buck99
03-07-2009, 09:46 AM
.....turned the right wheel (truck had no driveshaft) and the pinion turned but the left wheel didn't budge so I turned the left wheel and the pinion turned but the right one did not move.
It's an open diff.
The brakes are probably dragging a bit so the gear train takes the path of least resistance, which is through the pinion shaft. There's no drive shaft to stop it.
3834B
03-07-2009, 09:57 AM
Buck may be right here. Should of read a little closer. My 1973 has an 8 3/4 and it is a limited slip. I would still check it out. Not sure it is worth swapping a 9 1/4 for but the street guys love those rears. It's as close to a Ford 9" as you will likely find.
Speed Dragon
03-07-2009, 01:49 PM
I wish I could score a 3.91 sure grip in a junkyard :)
RAM MAN
03-07-2009, 01:55 PM
Spotters guide
dolfans
03-07-2009, 02:34 PM
in the pic for the 9 1/4 is the holes for the bolts?my truck is a 86 d150 and it has 10 bolts.it looks like the 9 1/4 except for the cover.it looks more like the 8 3/4.
RAM MAN
03-07-2009, 02:48 PM
yes, it is
cribbs74
03-07-2009, 05:00 PM
It's an open diff.
The brakes are probably dragging a bit so the gear train takes the path of least resistance, which is through the pinion shaft. There's no drive shaft to stop it.
There was absolutley no brake drag, I turned both wheels and they turned real smooth with no rub at all. Still could be an open diff though I suppose.
DiverDwnPowrRam
03-07-2009, 05:46 PM
another thing i remember about that Sure grip was the service center added a small can of..hypoid fluid???.. you guys correct me if i am wrong on that fluid. Anyway i was told that without that additive the diff would not last long.
3834B
03-07-2009, 08:19 PM
10-4
cribbs74
03-07-2009, 10:08 PM
It will be on the third member on the driver side. Likely a six digit number and you will just pay attention to the last three digits of the number.
http://members.tripod.com/~Mojo_Page/chry875.htm
OK, I took a look it is not the 489 but the 741. The weakest as described by the article in your link. That being said I could not find the ratio to see if it's the "S" sure grip equipped. The article says it's located on the identification boss on 64-72 8 3/4 which is what this is. So where is the boss? Thanks for the help.
buck99
03-07-2009, 11:13 PM
I've got a sure grip 3.55 in my 76 W100. I't's bin on standard 80 weight gear oil for 25 years. I put a limited slip additive in the oil and it works fine. The wheels still spin the way they are supposed to.
I have gone for several years at a time with no additives.
