489 Posi?

[STREETREBEL]

I found a used 489 posi on craigslist. What do I need to look for to make sure its good to go?
I know to look at the ring and pinon gears for wear.
Thanks.

 

[MarPar]

The first thing I would do is look and make sure its a Sure-Grip and not a Posi.

 

[STREETREBEL]

The first thing I would do is look and make sure its a Sure-Grip and not a Posi.

Thanks for the correction. Can you offer more that I should look for?

 

[MarPar]

Thanks for the correction. Can you offer more that I should look for?

Unfortunately, that is all I can offer.

maybe @Cranky can chime in. he is one of the best around here with rear-end questions.

 

[AR67GTX]

Short of tearing it down to inspect, or hooking up a splined hand bar on each side and trying to see if there is good resistance to turning one side while holding the other - you would probably be wise to expect to have to rebuild it.

 

[Kernel Sanders]

evidence of gear oil leakage from the seal... a quick check for excessive or to tight back lash (too tight may indicate someone had it apart already and didn't set it back properly... too much may be the same but also may indicate a lot of wear or worn bearings) I know, I know without a dial guage that's difficult to measure but I'm just talking obvious backlash issues...

 

[Cranky]

I found a used 489 posi on craigslist. What do I need to look for to make sure its good to go?
I know to look at the ring and pinon gears for wear.
Thanks.

Really need more info on it. Is it a cone type clutch unit or have plates in it? What do the bearings look like if it has them? This is what a cone unit looks like.

It's hard to tell the condition of the clutches without tearing it apart or having a tool like this to see how tight they are. I made these years ago to help during assembly plus checking. Stand on the bottom T handle and grunt on the top one. They are made from an old pair of axles.

This is what a SureGrip with clutch plates looks like. It's just not loaded into a case. The big one is for a Dana 60 and the small one is for an 8 3/4. Most times these command more money.

Unfortunately, that is all I can offer.

maybe @Cranky can chime in. he is one of the best around here with rear-end questions.

Thanks for that but there's several here that are well versed in rear ends

 

[MarPar]

Really need more info on it. Is it a cone type clutch unit or have plates in it? What do the bearings look like if it has them? This is what a cone unit looks like.
View attachment 443106

It's hard to tell the condition of the clutches without tearing it apart or having a tool like this to see how tight they are. I made these years ago to help during assembly plus checking. Stand on the bottom T handle and grunt on the top one. They are made from an old pair of axles.
View attachment 443107

This is what a SureGrip with clutch plates looks like. It's just not loaded into a case. The big one is for a Dana 60 and the small one is for an 8 3/4. Most times these command more money.
View attachment 443108

Thanks for that but there's several here that are well versed in rear ends

lemme re-phrase that...rear differentials lol

 

[khryslerkid]

Thanks for that but there's several here that are well versed in rear ends

I have a question for you Cranky, can you take a measurement (at the blue arrow) to tell how much clutch material might be left? I'm a novice on setting one of these up but reading about them I noticed there was a measurement taken at that location to make sure you have it set up right. I was thinking as the clutches wear, that measurement would become less? TIA

 

[Cranky]

I have a question for you Cranky, can you take a measurement (at the blue arrow) to tell how much clutch material might be left? I'm a novice on setting one of these up but reading about them I noticed there was a measurement taken at that location to make sure you have it set up right. I was thinking as the clutches wear, that measurement would become less? TIA
View attachment 443115

That's a new one on me. I have a Dana 60 unit sitting on the shelf with nearly new clutches in it and there's no gap in that area and have never noticed any units having a gap. The ramps are intended to put pressure on the plates when the unit differentiates.....or tries to spin one wheel when under power and if there's a gap, it won't work as intended.

 

[khryslerkid]

That's a new one on me. I have a Dana 60 unit sitting on the shelf with nearly new clutches in it and there's no gap in that area and have never noticed any units having a gap. The ramps are intended to put pressure on the plates when the unit differentiates.....or tries to spin one wheel when under power and if there's a gap, it won't work as intended.

Ok, makes sense. I'll have to find that info again.

 

[Daves69]

...........What do I need to look for to make sure its good to go?

Items I think I would look at - evidence of seal leak, excessive backlash, clearance at the cross pin, beat up companion flange, axle splines not aligned, chipped teeth.

Really, short of opening it up, you rely solely on the previous owners word and known history of the LS. You could gamble and install it like many of us did in the past as we did not have the proper tools (or the knowledge) or have a reputable shop open it up and find out for sure.

 

[Cranky]

Ok, makes sense. I'll have to find that info again.

I wouldn't mind seeing it too. Years ago I installed a set of new clutches and it locked up the unit good and tight. That's when I found out that there were thinner plates (2) available just for that. I do know that if you end up with plates that are too thick, it can keep the carrier case halves from fully bolting together and that might be where the gap on the spider gear shafts may show up? There can be differences in plate thicknesses and you have to be aware of that. I don't consider myself an 'expurt' with this stuff and it's been a really long time since sleeping at a Holiday Inn! IMO, the cone type SG's are much more simple to fix lol

 

[MarPar]

Hey Cranky, when you say cone-type, (generally speaking) you mean 741 and 742 cases, right?

no crush sleeve like the 489's?

 

[Daves69]

Cone type is more prevalent in the 489 I believe.............

 

[Cranky]

Yes, the cone units showed up later on in the 89 cases.....

 

[Cranky]

Cone type is more prevalent in the 489 I believe.............
View attachment 443138

Hey Dave, that one looks like it's in great shape...or nearly new. Is that yours?

 

[Daves69]

That's from the one I just did on a-bodies. Got super lucky on the cones I guess.........

http://www.forabodiesonly.com/mopar/threads/opened-up-the-old-489.381115/

 

[khryslerkid]

I wouldn't mind seeing it too. Years ago I installed a set of new clutches and it locked up the unit good and tight. That's when I found out that there were thinner plates (2) available just for that. I do know that if you end up with plates that are too thick, it can keep the carrier case halves from fully bolting together and that might be where the gap on the spider gear shafts may show up? There can be differences in plate thicknesses and you have to be aware of that. I don't consider myself an 'expurt' with this stuff and it's been a really long time since sleeping at a Holiday Inn! IMO, the cone type SG's are much more simple to fix lol

I was just thinking it would be a way to tell if the clutches need replacing without disassembly. It's stating that any measurement over .010 would indicate worn clutches.

From the 1962 FSM

 

[STREETREBEL]

I just went and looked at it. It was a 489 cone type. Gear wear looked good.
Pinion play was minable. Had just a few specks of surface rust. He wanted
$300 for it, but I didn't buy it because it was a cone type.