Rear End lets go after only 300,000 miles !

[Edward J.]

Re: Jack is very happy with new rear end !!

Jack was glad to help keep the ride a live and the dream of your next adventure going. So many of us here on the TDB have watched and read your posts as you took on the world with your corvette, There are truly not many like you. I guess maybe at some point you could write your book on Jacks adventures around the world with his little green Corvette. Let us know when your up and running.

[Jack P.]

It has been 49 years since a pro touched my shafts

Last time was at the factory 49 years ago. I have sent off my drive shaft and half shafts for a professional balance and u-joints replacement. the drive shaft will be balanced with a new slip yoke that is needed. The old one had 300,000 miles on it ....


This is a local shop that deals with a lot of construction equipment and truck shafts. Shops are getting harder to find now.





Look at the size of the shaft next to my little guys







Update on car restoration....yes...it seems like it is turning into a restoration from just a stuck transmission plug.


Ed Johnson had donated a 78 rear with the good Eaton Posi unit (it will be ) to me and I have just shipped it off to Gary Ramadei, who many know of for his rear end, TA and steering box rebuilding skills.


He is going to tune it, replace the clutches with metal ones, and put in 3:36 gears instead of the current 3;70. With my wide ratio Muncie , the car will be back to original gearing that I changed out in 1972 ish....


On the way to Gary Ramadei





When done, I will have replaced all rear suspension rubber bushings, strut rods , spring bushing, shaft balancing/joints, body mounts and bushings and maybe the throw out bearing ...mufflers and pipes...lets see...did I miss something.......

[Gary R.]

Re: Looks a lot better than this one...

I got the diff in today and checked it out. It was the typical late 70's diff. This is a good core but there were some common issues with it that they all had - axles were worn 065-070", the ring gear bolts used were not as good as the ones used pre 76-77, the clutches were what I coined "snowflakes" but they were not broken so the diff wasn't beat on as some are. If so those clutches would have come out in pieces. I sent Jack a lot of pictures he can share if he likes. The diff is now apart, old parts tossed out, and I'm cleaning up the rest.

[Jack P.]

Re: Rear End lets go after only 300,000 miles !

[Jack P.]

Re: Rear End lets go after only 300,000 miles !

Update on rear end and suspension rebuild..


Gary Ramadei is rebuilding the 78 rear end that Ed Johnson donated to the project. Here are some pictures of his inspection and comments.


"Looks like this came out of a 79 vette. The gear date is Aug 1978, maybe it made it into a later 78? Doesn't matter the 78 & 79's were ok but did have some areas that were weak. The clutches, ring gear bolts, and axles were bad and this one is typical as it has all those bad parts. They are not going to be reused though, I will use the best parts and that will make a difference. The axles had 065-070 endplay and were mushroomed over. These are just good for cores now. There were no broken snowflake clutches so that means this diff wasn't beat on much, otherwise they would be broken. The ring gear bolts used from 77-79 were junk. They stopped using lock washers and the bolts didn't have the shoulders like the older ones did. I will use ARP bolts, you can see them next to each other in the pictures."




Parts not being used.....





Disassemble rear

[Jack P.]

Re: Rear End lets go after only 300,000 miles !

Here are pictures of the posi case before polishing. Polishing is done to prevent cracks from forming.

[Jack P.]

Re: Rear End lets go after only 300,000 miles !

[Jack P.]

Re: Rear End lets go after only 300,000 miles !

Same case after polishing

[Jack P.]

Re: Rear End lets go after only 300,000 miles !

[Jack P.]

Posi Unit Update assembly of Unit

We are reworking a 78 Corvette Rear from 3:70 to 3:36 , plus tuning it.


Gary is doing the rebuild and here is a quote from him on bolts that attach the Ring gear.


"Here I countersunk the posi case ring gear holes. You see in picture#1 that the holes are square edged and the stock bolts work with that but not the ARP's. The ARP's have a larger radius under the head for more strength and have the shoulder on them like the old GM bolts did. Somewhere around 1977 they changed to the bolts that were in here before, shorter, no shoulder, and not loctited in place. Not good, many backed out in use sometimes within the factory warranty period. QC with the late 70's vettes wasn't as good as the earlier cars but that is probably the case with most lines of the period."


Stock bolts vs ARP's Stock on right





Before milling notice flat surface





Counter sink

[Jack P.]

Re: Posi Unit Update assembly of Unit

Cut





Polish





Perfect fit

[Jack P.]

Assembly of Posi Unit Update

Gary is now assembling the posi unit after polishing.


Here is his commentary on the process.


Here I radiused the spider teeth to prepare to tune them. I used new solid steel clutches, new cross shaft, retainers, and washers. Next up the tuning process starts. Unlike a stock posi, where the spider lash is set between 002-008" and then the plates and springs are stuffed in there, I will set the posi up to a balanced, much more precise unit then any stock or rebuilt vette posi. where it is now I could just use the springs but it really works better to put the time and machine work in to tune them.



Pictures Parts laid out





Cross shaft and steel clutches

[Jack P.]

Re: Assembly of Posi Unit Update

Radius Spider Teeth








Ready to Tune





Next series will be the tuning


Jack

[Jack P.]

Tuning the Posi Unit

Gary is now ready to tune the posi unit. Here is his explanation of the process.


"Here I started to tune the posi. While some think you just remove the springs and plates and bolt it together, there is much more to it. The process requires running in the new clutches to "seat" them. This will change the lash after about 50 rev's but I go at least 300 per side, CW & CCW. Then check it on the bench fixture and re-shim. The shims come in 005 increments so I grind them to within 001" to dial in the tune. The end result is a balance setup between both the Left & Right sides. The naysayers will tell you it will not work, yet Tom's has been building them like this for over 40 years for street, strip, and road race cars. You will have full posi action yet there won't be any hammering in the corners and there is less load on the clutches. All my vettes are setup like this and work great."



Video of process

Just click on picture for video

[Jack P.]

Re: Tuning the Posi Unit

Continuing the rebuild, we are now preparing the case . It must be cleaned both inside and out. Here are comments from Gary on this procedure.


"Here I worked on the housing, cover and pinion yoke. I finished blasting them to bare iron. Now most places will just shoot a cheap top coat of paint and call it done. I never liked that since once the car is in use that paint isn't going to last as long as it should. So I blast the parts to bare iron. Then Etch them for 30 minutes, rinse, blow dry, flame dry, cool, POR15 and then when just right shoot the top coat to mix with the POR15 and harden together. I'm waiting for the POR15 to setup now to shoot the top coat. Then I'm going home to fire up my 72 vette for a weekend ride!
"


Blasting first





Etching