489 question

[dgie]

I have a 489 case in my car (suregrip or not, not sure ) and find that when I drive the car on the highway, the RPM's are pretty high. I want to go back to a 3.23 which I believe would be stock, the guy I bought the car from swaped out the original for some high perfomance setup and I want to go back, for highway use. Is this something that an average individual is able to do, or is this something that I would have to take to a drivleline specialist and pay what they quoted me $1400 dollars to do for me. I really would like to do this myself if possible, that way I can save the $1400 or so, so I can fill my gas tank at least once at these gas prices (sarcasm). I belive that I would be changing the pinnion and ring which I found for around $200.00, what else am i missing, if I undergo this venture on my own? also any manuals on this rebuild available?

[aifilaw]

A ring and pinion change is a relatively easy swap.
the hard part is resetting your pinion angle, and although I wouldn't recommend it for a anyone but an expert if you want it done right, it is possible to do if you read up on it fully.
Buy the parts you want online and then take it to a knowledgeable shop and have them do the work for a set hourly rate.... its a 1-2 hour job.
Also, not a bad idea to freshen up your center section (Sure-Grip) while you are under there if money allows, it will save you a headache in the end.

[Just 6T9 CHGR]

The 8¾ center section is very easy to swap.  A 3.23 gearset fully assembled are pretty easy & cheap to come by.  Maybe you can buy a complete center section & swap out when the need arises?

[kab69440]

I'll swap you a 3.23 open pumpkin for your current set-up.  I'd like to have a set of quarter mile gears, you know, "just in case"... I don't suppose you are anywhere close to cental Ohio, are you?

[Chatt69chgr]

What you can do is to surf the net and read everything you can find on this to familiarize yourself with the procedure.  Then, buy your gears from Strange Engineering.  They have American made gears and they have the best price.  You can get the original Timken bearings from Autozone as well as the seals.  I don't think anyone else has this brand of bearings.  You can use the original crush sleeve when installing the bearing.  I think this is the way all Chevys are done.  Or you can buy shims and a solid sleeve from RA Tech which would essentially convert the pinion setup to the same as a 742 which some prefer.  If you have a suregrip, it's probably a cone type.  They don't sell rebuild kits for them.  Maybe it's working OK as is (if it's not, they can be made to work again by machining the cones and shimming them out but few know how to do it).  The plate type has a rebuild kit available from the dealer who also has new thrust buttons available if needed. 

I would not attemp to do the rebuild myself---it takes special tools and experience and if you mess it up, your ring and pinion won't last long.  Just source the parts yourself and take the pumpkin and parts to somebody in your area who is good.  It's not whoever quoted you $1400.  You ought to be able to get someone to rebuild it for no more than $250 max.  Go down to the local dragstrip and seek out the Mopar guys.  They will tell you where to get it rebuilt.  You can buy a whole new 489 case with gears (w/0 suregrip) for around $900.

With all this said, it is possible to rebuild it yourself.  As stated, the hard part is setting up the ring and pinion.  I have always wondered if there wasn't a video of this available.  Or a real good booklet.  If anyone knows of such, I would llike to know about them.

[dgie]

Well it sounds like it might be a good idea for me to take it to someone since 250.00 is not bad. I have the service manual on the car on cd rom and they go thru rebuild procedures, but looks like they are using a lot of special tools. Ok, so now I am at the point of needing to pull the center section, 3rd member, pumpkin (all the same component with a different name I assume) out of the the differential still mounted in car. what is the procedure at this point, do I need to take measurements for end play and pull the axles to allow this part to come out, or do I just loosen the center section and pull it off with all the oil that comes with it? also where is the sure grip if it has one, is it in the center section, or? If I decided to get another center section just out of curiosity would I just unbolt the old one pull it off and bolt the new one on, which goes back to my earlier question on how to get the center section off.

[Chatt69chgr]

To pull the center section, you have to take the brake drums off and then take the 5 bolts loose holding the axles to the housing and pull the axles out about a foot or so.  Probably best to just take them out since you might want to replace the oil seal in the end of the housing on both sides.  Best to loosen the bolts all the way around the centersection and gently pull the center section out enough to let the oil drain out into a pan (need to drop the driveshaft first).  Now, carefully remove all but one bolt and put a floor jack under the centersection and then pull it out and let it down.  You can also do like I did and put a pan below it and let it drop into a big pile of folded up towels.  You will adjust the axle endplay with the adjuster on the right hand side when you put it all back together.  Look at the attached pictures to see if you have a open rearend or one with a suregrip and, if so, what kind it is.  The plate type uses thrust buttons that stick into each side and these often get stuck to the ends of the axle shafts and get lost.  And yes, you can just replace the whole assembly with another one.  You do need to be careful about the pinion yoke.  These cars came with either a 2-1/8 inch yoke (a 7260) or a 2-5/8 inch yoke (a 7290).  They do make U-Joints that are 7260 on one side and 7290 on the other however.  The 7290 is stronger but if the rest of your driveline was originally 7260, the slip yoke on the transmission will be a 7260 too so you wouldn't gain anything going to the 7290 for the pinion yoke.  I am just telling you this in case you found a center section with the proper gearing that had a yoke that didn't match up with whats in the car now.

[dgie]

Is the sure grip located in the center section? where it will come out with the center section when I pull it.

[doctorpimp]

Is the sure grip located in the center section? where it will come out with the center section when I pull it.

Yes, the ring gear is bolted to it.

[dgie]

how do you determine if it is a 7260 or 7290? lot of questions I know

[Nacho-RT74]

width...

2 1/8" inside yoke is 7269
2 5/8" inside yoke is 7290

[dgie]

stamped anywhere?

[Just 6T9 CHGR]

stamped anywhere?

No..... bring tape measure

[dgie]

update, I pulled the 3rd member and axles and brought them to get checked out at a local shop. Everything made sense once the 3rd member was out. Looks to be clutch type sure grip. I told them to pull it apart and tell me what it looks like and what I need. Hope all goes well with this rebuilder, have not had a lot of luck lately finding builder who are not trying to work me one way or another.