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WOW! That is one of the worst cases of "customer service" I have ever heard of! I used to be responsible for a 24 person customer service department that handled 800 calls a day. Someone would get fired for a statement like that.
Don't be nervous, knowledge is your power. The more you know then you can tell who is full of it and who is not. Ask any rebuilder you speak with if they polish and tune Eaton posi's. If you get a yes, then have them show you what they do. If some are selling new gears, ask whose gears they are. Many rebox gears, so Joe Schmo vette shop tells you they use their own gears, it is pretty much a lie. They tell you that a posi won't work without the spring pack- same as saying we don't know how to tune a posi or it takes too much time. They say axle endplay is good wherever it ends up is saying we use as is parts and procedures and if the axle endplay is 025 or 040 or 010 it is good. I can go on but I think you get my point.
I still have my original one. It needs rebuild but is in great shape. I only took it out because a thrust washer was cracked. Rather than rebuild I bought the Yukon one. It's been great, I don't drive at the race track so it's plenty more than I'll ever need. Unfortunately I'm in bc canada so can't get this chunk to you. But it's available if you know a way.
Thank you very much for your kind and generous offer. If I need to take you up on it I will find a way.
Cracked posi case, this one let go before caught. It happens.
Yukon cases are not as good as Eaton, in my opinion. Both imported, both use lousy clutches.
USA made Eatons are thicker at the window and better than both new Eaton and Yukon, but also obsoleted now. The Eaton cases are machined better-in China- then the original USA made cases installed in the cars. It kills me to say that but it's true.
The assembly of a new out of the box posi has to be checked. I never used them out of the box, they always come apart and I rebuild them before I will use them. Many times, the assembly is sloppy, but with fiber clutches and huge springs, you will never know. At every turn you are smudging the fiber off into the oil. It will black in no time. They use one less clutch plate and disc per side.
I used 3 new ones over the past month. Prices keep going up and backorders are common.
78 diff's also had bad axles and ring gear bolts. You might save money finding a good used core with a good posi case.
If you still rebuild 76 differentials, I would like you to do mine. contact me Curtis 76
So if I were you I would order a new Eaton posi now and have it shipped to your Hotel. I have done such a thing before. They can hold it for you.
Since you have a week lead time and a week in the US it might work just fine.
Your next step is to have the shop put the side yokes in the posi with the center pin and see how much slop there is. Gary likes .006" inch. Many wear and have .250 or more.
Or measure the yokes from the top of the c-clip groove to the top of the shaft. A decent not too worn side yoke should measure around .185".
If yours are badly worn, and 78s tend to do that, you may need new side yokes as well. And good ones are harder to find than posi units. But at least they only weigh 5.8 lbs each.
These are about .185" Sometimes the beveled end is worn all the way off, or even also the entire c-clip groove.
Hello, OP here again. Sorry it's been so long since my last post. Thank you to everyone who contributed to the thread.
I didn't have enough time to make progress with this before my trip to Las Vegas, and, sadly, my trip did not go to plan, so I made no progress while I was in America.
Anyway, I have been on the Yukon website, and I've been chatting with a very helpful Yukon employee who suggested this:
So presumably that all fits into my original housing? So I need to find someone here in the UK with the appropriate skill-set to assemble/build it all for me? Alternatively I need to get my housing to America, or buy a new one, and have someone in America do the building and ship the finished unit to the UK for me.
Sorry for all the baby-questions and thank you again for all the help.
We have a term here called-"clipped" meaning you were taken or scammed. You can certainly do as you please but taking the advice you were given by the very helpful employee of the company he represents would not be in your best interest. good luck.
I think if you make a couple more posts then you will be able to PM Gary.
Honestly even tho you are in the UK, IIWU I would still send it to Gary.
Too few "diff guys" out there understand the Diff Yokes can wear badly, and have a big effect on the handling feel.
The diff housing itself and hopefully the ring gear??, are the only re-useable parts left in there.
Shipping it back & forth to USA would be expensive, but it will be done right and less expensive in the long run.
You could buy a new Eaton posi and have it shipped direct to your UK guy, but do they know how to tear it apart and inspect it?
You could order solid clutch discs and have them put them in.
A lot of your choices depend on how much HP do you have / want and how hard are you going to drive it?
And have you measured the axle stubs yet? That's just as critical to your repair.
If you can find a mechanic who is well versed in differential builds there in the UK and they are willing to work with you on how to properly build the Corvette differential, you might be better off spending local labor pounds vs paying for shipping and import taxes.
Leigh1322, myself, and many others have built their own differentials after researching many posts on how to do this properly. Gary (gtr1999) has, by far, the most experience with these and will build you the best there is but you don’t have to incorporate each and every trick in the book. There are some basic recommendations (e.g., “tuning” the posi, foregoing use of the spring packs, using steel clutch plates, deburring/radiusing the casting flaws in the posi case, and ensuring the axles are properly hardened, etc.) that your mechanic can incorporate but things things like steel cap for the left journal, cryo treatment, REM polishing, 30 spline axle conversion, machining the cross shaft retention bolt land can be foregone if your expectations are simply to have a dependable unit for normal driving.
Gary is very generous in providing advice and we are glad to offer our experiences as well.
Thank you for contributing. I have pretty much given up trying to find someone here in the UK that I can trust to build for me. All I would like is a well built standardish diff that will be reliable - it doesn't need to be anything fancy, just done right.
Your picture looks impressive but a little daunting.
Polish/round the edges of the windows if you are really feeling ambitious, but not likely needed. Look at the window corners closely and then decide. You do not want a sharp edge, that is a "stress-riser".
Buy Timken bearings & SKF seals
Have your diff guy assemble it - R&P, backlash, seals, bearings, etc. That part is mostly "normal" The assembly can be basic if your needs are stock "driver"
Ask him or coach him how to assemble & seal the pinion seal area so it does not leak. Leak test it like Gary does. Front leaks are very common and these are way worse than other cars to remove the diff again.
2 more things:
You still need to address the axle stubs, Do you have a measurement yet? That will determine if you need new ones.
Does the ring & pinion have any chips?
