Differential Cover - Impala Tech
Transmission & Driveline Transmissions & Differentials

 
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post #1 of 13 (permalink) Old 09-12-2019, 11:31 PM Thread Starter
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Differential Cover

Looking at rebuilding the 8.2 10 bolt and I was wondering if anyone has
the aluminum strengthened covers? Perfect Launch and Mosier come to mind.
Any clearance issues between the cover and the panhard bar?
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post #2 of 13 (permalink) Old 09-13-2019, 04:10 AM
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Quote:
Originally Posted by Impfan View Post
Looking at rebuilding the 8.2 10 bolt and I was wondering if anyone has
the aluminum strengthened covers? Perfect Launch and Mosier come to mind.
Any clearance issues between the cover and the panhard bar?
Gale Banks tested all of the Diff covers made products made on a diesel truck to see if they did anything. He discovered that they did. They killed bearings, fuel economy, and destroyed pinions.


Now if you need the bling, I hope you are running air lift suspension so you can put it on display at a car show.

Big Dave
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post #3 of 13 (permalink) Old 09-13-2019, 09:18 AM
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Yes, it *might* interfere with your panhard bar. I installed a Moser 12 bolt rear last winter. I have a ChassisWorks adjustable panhard bar and there were clearance issues between the two parts. I ended up grinding a little over an 1/8" of material off my panhard bar just to be comfortable with clearance. A stock bar is much smaller in diameter and may not have caused me any issues.
Since I was spending the money on a full Moser built rear end, I did mostly get the aluminum cover for looks but I'll depart from Dave's assessment because I do not have the finned cover being described in the video. I have the girdle cover.
https://www.moserengineering.com/711...lt-gm-car.item

1969 Imapala convertible build thread here:
https://www.pro-touring.com/threads/...ghlight=impala
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post #4 of 13 (permalink) Old 09-13-2019, 12:17 PM
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Yes, there will most likely be a clearance issue between the covers adjusting bolts and the panhard bar.
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post #5 of 13 (permalink) Old 09-13-2019, 05:46 PM Thread Starter
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Watched the vids. I guess it all depends on what one is running and the amount of driving one does.
I don't own a duelly 3/4 ton that climbs steep hills or pulls tons in weight.
The stock steel diff cover in place since 68 has served it's purpose.All bearings remain intact. No noise from the back end.
I was surprised though to learn, that those old cal Custom "ET" finned aluminum covers are only 3" in height?
To look at pics of them, one would swear the height of those things would be 5" any day of the week...
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post #6 of 13 (permalink) Old 09-13-2019, 06:11 PM
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Outer wheel bearings in all Dana-Spicer rear ends are fed from the round hole located high on the drivers side. That Inverted V stamped into the rear cover isn't to provide structural strength, but capture gear lube slung off the ring gear. The housing is machined to feed both sides and the front (driveshaft side) pinion bearing from internal oil passages.

That said the SAE 90 weight gear lube (or 85-140 multi grade) oil isn't going any where until it heats up. As you can see with the plastic rear cover to watch the inside once it reaches operating temp it flows like water.

NASCAR uses a positive displacement oil pump, driven off of a pulley bolted to the rear yoke, to force oil to the bearings after it goes through a cooler because at 140 to 200 miles an hour it thins the grease out to the consistency of a light lubricant similar to WD-40 after hours of racing. A light oil isn't a way to lubricate roller bearings.

Further I never was on the clock as an employee at my local Chevrolet dealership from the mid sixties to the mid eighties I practically lived there. If you drug a car in for a warranty claim on a broken rear end and they saw an aftermarket cover on the differential the warranty writer would automatically void the warranty due to lack of oil. Even if you broke the ring and pinion drag racing, just the cover meant you bought a new rear end.

Finally in 1972 GM switched from Spicer as the vendor for rear ends to American Axle Works (the folks that made the 14 bolt rear to replace the Dana 60 under light trucks, and the 7.5 inch ring gear found under the Vega). Their "Corporate 10 bolt" better known as the 8.5 rear has no stamped V to divert gear lube to the bearings. I actually have no idea how it lubricates parts so I can not comment. But since it is flat rear cover might be fine with this rear end.

I never used a cast rear cover with the preload bolt (from an engineering point of view it is a good idea). Instead to reinforce my 12 bolts (back when I still ran a 12 bolt was to replace the cast iron saddles with steel caps and then remachine the rear end after welding the tubes solid. The larger thicker bearing saddles where stronger than a stock cap and a cast cover. After my third modified 12 bolt failure I switched over to a Dana 60 and never had a broken rear end again.

Big Dave
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post #7 of 13 (permalink) Old 09-15-2019, 09:00 AM Thread Starter
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Thanks Dave for the info on the 8.2 differential. I'll be sticking with the OEM cover, as the aftermarket ones
will interfere with the pan hard and that due to the design of the OEM cover, it benefits the internals with lubrication.
I'm looking at moving up a notch from 3.08 highway gears to 3.36. I figure with little to no highway driving hence mainly street driven
and with a powerglide, going a little steeper in rear gears would improve things. I may have to swap out the speedo gear as well.
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post #8 of 13 (permalink) Old 09-15-2019, 01:34 PM
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3.36 is an improvement over the 3.08 but I would look to see if you can find a 3.55. Common ratio for pick-ups, not so much for cars. But it is as high as I would go with a 1:1 final drive ratio in the tranny.

You can gain the benefit of lower gearing with an OD tranny but the engine needs to be spinning above idle at cruise speed. That is why an OD and 3.73 rear gears is so common at car shows, best of both worlds.

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post #9 of 13 (permalink) Old 09-15-2019, 10:50 PM Thread Starter
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Quote:
Originally Posted by Big Dave View Post
3.36 is an improvement over the 3.08 but I would look to see if you can find a 3.55. Common ratio for pick-ups, not so much for cars. But it is as high as I would go with a 1:1 final drive ratio in the tranny.

You can gain the benefit of lower gearing with an OD tranny but the engine needs to be spinning above idle at cruise speed. That is why an OD and 3.73 rear gears is so common at car shows, best of both worlds.

Big Dave
I was debating 3.36 or 3.55 both ratios are available through Yukon. What would be the benefits of going that steep of a gear ratio?
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post #10 of 13 (permalink) Old 09-16-2019, 12:20 AM
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Rear gear multiples engine torque. Acceleration is all about torque. If you have a 283 pushing a heavy car you need a steeper gear.

Example a bread truck (step van) is a two and a half ton truck powered by a six banger. The motor sings high C going down the road due to 4.88 to 5.13 rear gears. But it spends most of it's life parked in front of stores at four AM, being unloaded as opposed to driving.

Now if your big Impala has a 427 it won't need as much of a rear gear to get the car going. With a bigger motor, you get more torque: made the old fashion way; with displacement.

The six cylinder in the bread truck burns as much gas as a 427 does in a big car. You gust get more grins per mile with the bigger motor in the Impala.

Big Dave
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post #11 of 13 (permalink) Old 09-16-2019, 10:38 PM Thread Starter
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Dave I have a crate 350 with an Eldelbrock intake and 600cfm 4 barrel carb with header exhaust.
If I go with a steeper gear ratio, will I have to change the driven speedo gear?
Running P24560r15 T/A's on the rear. Currently have the blue 20 tooth gear in the tail shaft.
There's a formula for calibrating the speedo when gears and tires are changed apparently...
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post #12 of 13 (permalink) Old 09-17-2019, 12:57 AM
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I buy the gears these guys recommend:

https://transmissioncenter.net/produ...dometer-gears/

then I go to the speedo shop in town to get them calibrated once I install them, tested and certified at 15,45,55,70, and 90 mph.

Every time you change the rear gears you should change the speedo gears to match.

Big Dave
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post #13 of 13 (permalink) Old 09-17-2019, 12:27 PM Thread Starter
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Quote:
Originally Posted by Big Dave View Post
I buy the gears these guys recommend:

https://transmissioncenter.net/produ...dometer-gears/

then I go to the speedo shop in town to get them calibrated once I install them, tested and certified at 15,45,55,70, and 90 mph.

Every time you change the rear gears you should change the speedo gears to match.

Big Dave

Thanks for your help, Dave
Much appreciated..
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