1968 Impala Differential Question - Impala Tech
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post #1 of 14 (permalink) Old 03-17-2015, 02:51 PM Thread Starter
 
 
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1968 Impala Differential Question

Hello everyone,

I took my impala to a mechanic today. Once it was raised we looked under the body and saw exesive leaking from the differential. We then took it for a ride and noticed a clanking noise during acceleration. The mechanic suggested replacing the differential for $1500.00. I told him I would think about it, I wanted to check with the experts here before I just start dropping money. I'm stationed here in Izmir, Turkey and don't have access to our usual auto hobby shop and tools to work on it my self, so I am basically left with no choice but to get the work done here. I was under the impression that it was my exhaust clanking against the axle, I'm yet to rule that out though. But let's say it is the differential. Do I need to replace it? What will determine that and is 1500 a reasonable price?

Thank you

Jon
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post #2 of 14 (permalink) Old 03-17-2015, 07:56 PM
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Before you spend the money

First off, if you lost a lot of fluid the rear would not be getting lubricated and cause all kinds of noise. If he took the car for a ride after seeing the leak and did not first test fluid levels, try to find a new mechanic. Lastly, this may be an issue of only needing a new gasket. I suggest, pulling off the cover and thoroughly cleaning the entire inner gears. Replace the gasket, cover and re-fill. If this is a posi also add the GM posi additive that helps prevent posi-knock. They this first before dropping $1500 please,

Paul

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post #3 of 14 (permalink) Old 03-17-2015, 11:08 PM
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Paul is correct there are two sources of an oil leak at the front of the differential. The first and most obvious is a worn out grease seal. Costs about $3.50 to $5 to buy a new one. The second issue is a lack of sealant (I use RTV now but the factory used a shellac or lacquer sealant when new) to keep gear oil from wicking up the splines on the pinion shaft that the universal yoke is bolted to. The most likely source of the clunking is a worn out universal joint. They are easily replaced with hand tools and a bench vice with a five or six inch jaw opening.

Big Dave
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post #4 of 14 (permalink) Old 03-18-2015, 04:27 AM Thread Starter
 
 
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Thanks for the feedback fellas. I have ordered the parts. I Well let you know the outcome, and how much it will run to have it installed out here (different shop).
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post #5 of 14 (permalink) Old 03-18-2015, 09:14 AM
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Quote:
Originally Posted by JonFernandez305 View Post
Thanks for the feedback fellas. I have ordered the parts. I Well let you know the outcome, and how much it will run to have it installed out here (different shop).
Hopefully your new mechanic knows that the spec is for used bearings is 26-28 in./lbs. (torque required to rotate the nut against friction of the assembly). If for some reason you replaced the pinion seal with new bearings you would torque it to 30-38 in./lbs.

If you are in a sand pit with only a crescent wrench and a punch for tools and MacGyver is your mechanic you can punch the nut and pinion shaft to get a feel of where the nut needs to wind up once it is tightened up by feel.

Big Dave
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post #6 of 14 (permalink) Old 04-22-2015, 07:57 AM Thread Starter
 
 
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Good day everyone. My parts finally came in, and I might actually be able to do the work on post with two friends. My question is for the differential fluid. Is there specific type that my Impala requires (viscosity) and what is the quantity needed? Thanks for your help again.
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post #7 of 14 (permalink) Old 04-22-2015, 11:06 AM
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SAE 80W-90 weight gear lube. I use Valvoline High Performance Gear Lube and then I added GM Fluid Limited Slip Axle Lubricant Additive part number 88900330. You can buy it from Amazon dot com if it is not available in the corner auto parts store. It should take a little less than two quarts/liters to fill the rear end by way of the fill plug. You keep pumping fluid into the rear end slowly (to give it time to fill the void) until the fluid level reaches the bottom of the threads of the fill plug.

http://www.amazon.com/Genuine-88900330-Limited-Lubricant-Additive/dp/B0028CMPIS .

Big Dave
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post #8 of 14 (permalink) Old 05-07-2015, 08:35 AM Thread Starter
 
 
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Hello friends,

Today myself and a couple colleagues swapped out the old rear U joint with the replacement. We had a hard time putting in the new one. At first, we did not line it up right. Not paying attention, we where forcing the joint into the drive shaft and it would not fit properly. Realizing this, we removed the joint and noticed that there was a small warp from where the U joint was grinding against the drive shaft. We fixed this by sanding it down and making the surface smooth once again (it wasn't to much). To cut to the chase, we ended up taking off the caps and basically putting on the U joint and then hammering the caps to lock the joint in place. Once we finished, the U joint was real tight and it was not pivoting smooth, it required a bit of force to move it from left to right. We installed the drive shaft again and took the car for a test ride and immediately it started making a real loud squeaky sound when accelerating. This noise would only cease when you let go of the gas. What could be the possible cause of this noise? The U joint is to tight? Damaged? Not the proper size/piece?

Thank you.

Last edited by JonFernandez305; 05-07-2015 at 08:37 AM. Reason: Grammar
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post #9 of 14 (permalink) Old 05-07-2015, 09:30 AM
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Sounds like you need to buy another U-joint and then watch a few U-tube viddeos explaining how it is supposed to be replaced.

Big Dave
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post #10 of 14 (permalink) Old 05-07-2015, 12:55 PM
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U-Joint

Agree with Dave. Perhaps some of the pins dislodged and fell to the bottom of the cap which would not allow the cap to sit properly. Review this youtube video and hopefully it may help you:

http://youtu.be/rOEdul7nscY

Paul

Paul

1966 Impala SS

Please Visit our new site:
http://www.winvoices.com/
1959 through 1988* window stickers, car shippers, dealer invoices, retail sales orders and tank stickers, expertly reproduced, for most Chevrolet Models.





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post #11 of 14 (permalink) Old 05-07-2015, 06:38 PM
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You have u joint bearings in the bottom of the caps.
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post #12 of 14 (permalink) Old 07-27-2015, 06:29 AM Thread Starter
 
 
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Hello everyone,

Wanted to just let all of you know that my differential issue has been resolved. Thank you for all your help. Now on to replacing the convertible top.

Thanks!
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post #13 of 14 (permalink) Old 07-27-2015, 11:26 AM
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Find you a good guy to do the top.
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post #14 of 14 (permalink) Old 07-29-2015, 01:04 AM
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I was in Turkey last year.

Stay safe
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