Rear Differential Question.

RonLiv · Jul 18, 2018

69hemibeep said:
View attachment 26149

Obviously again, I'm no expert. But I still don't think this is a Chrysler rear diff. The 8.25 is a 10-bolt, but shows a drain plug hole, his picture does not have this. It looks more like the GM 10-bolt to me per the picture above maybe?

69hemibeep · Jul 18, 2018

What kind of wheels are on it, Chrysler, Ford or universal to where a Chevy would fit? I doubt anyone slipped custom axles into it.

1778ppr · Jul 18, 2018

FWIW, it looks like an 8-1/4" rear end to me. The drawing above is misleading as to what an 8-1/4" actually looks like. Yours looks like an 8-1/4"
John

RonLiv · Jul 18, 2018

1778ppr said:
FWIW, it looks like an 8-1/4" rear end to me. The drawing above is misleading as to what an 8-1/4" actually looks like. Yours looks like an 8-1/4"
John

Doesn't the 8.25 Rear Chrysler Diff have a drain plug? His does not.

1778ppr · Jul 18, 2018

You could be correct. I'll try and remember to take a look at my '76 Fury Sport. It has an 8-1/4" in it. I cannot remember if it has a drain plug in it or not. I think the 8-1/4 covers varied over the years.

RonLiv · Jul 18, 2018

1778ppr said:
You could be correct. I'll try and remember to take a look at my '76 Fury Sport. It has an 8-1/4" in it. I cannot remember if it has a drain plug in it or not. I think the 8-1/4 covers varied over the years.

Nothing would suprise me with Chrysler! But that picture sure looks like a 10-bolt Chevy diff to me.

Russ69Runner · Jul 18, 2018

Yep me too. To many factor's point to that. The cover seam's to be a dead give away. Also the 10 bolt for the cover.

RonLiv · Jul 18, 2018

Russ69Runner said:
Yep me too. To many factor's point to that. The cover seam's to be a dead give away. Also the 10 bolt for the cover.

If it is a 10-bolt GM diff, what the heck is it doing under a Roadrunner!

Hodgee · Jul 18, 2018

RonLiv said:
Again, I'm no expert and I don't know if parts are interchangeable by different manufacturer's but Chevrolet made a 10-bolt(and a 12-bolt) pattern rear differential in 1968 that is circular like the picture shown here. I'm doubting this is a Chrysler rear, but again I don't know much.

The only thing i have to go by is pics and it does have the pinion snubber on it.

Hodgee · Jul 18, 2018

69hemibeep said:
What kind of wheels are on it, Chrysler, Ford or universal to where a Chevy would fit? I doubt anyone slipped custom axles into it.

It has the Magnum 500 wheels on it.

RonLiv · Jul 18, 2018

I found this, more reason I don't think this could be an 8.25 Chrysler diff. Doesn't look like it would be a good choice for a 69 Roadrunner with a HP383. Not to mention the diff would have one of the three casting numbers:

8 ¼
Introduced in 1969. This rear end will be found in all Darts / Valients from 73 - 76 and also can be found in 340 Dusters and other A bodies. There is a sure -grip available beginning in 1973. This axle while not a real high performance piece is certainly good enough for a mild street car. So if you go for a disk brake swap and are pulling out those spindles etc. out of your 73-76 donor car just grab the rear and you will have a nice 4.5" wheel pattern all around and way better brakes to boot. Sure-grip units are commonly found in Diplomat cop cars throughout the 80's but that rear end is a bit harder to install than the 73 -76 due to the strange leaf spring mounting pads. These pads can be cut off the axle and replaced with more conventional ones if you wish. If your short on cash and you can't afford to get a 8 ¾ or find the time to locate the long 8 ¾ axles for re-splining the 8 1/4 is a real nice alternative for a while and CHEAP in the yards ($50.00 non sure-grip and $125.00 sure-grip here in Texas). You may never blow up the 8 1/4 with a mild small block street car.
Castings: 2852905, 3723598, 3723599
Info: 1 5/8 pinion, 57.6" wide, 10 bolt cover, 55.6" width (flange to flange) / 51.4 housing flange to flange / 43.02 spring seat center to center.

Hodgee · Jul 19, 2018

RonLiv said:
I found this, more reason I don't think this could be an 8.25 Chrysler diff. Doesn't look like it would be a good choice for a 69 Roadrunner with a HP383. Not to mention the diff would have one of the three casting numbers:

8 ¼
Introduced in 1969. This rear end will be found in all Darts / Valients from 73 - 76 and also can be found in 340 Dusters and other A bodies. There is a sure -grip available beginning in 1973. This axle while not a real high performance piece is certainly good enough for a mild street car. So if you go for a disk brake swap and are pulling out those spindles etc. out of your 73-76 donor car just grab the rear and you will have a nice 4.5" wheel pattern all around and way better brakes to boot. Sure-grip units are commonly found in Diplomat cop cars throughout the 80's but that rear end is a bit harder to install than the 73 -76 due to the strange leaf spring mounting pads. These pads can be cut off the axle and replaced with more conventional ones if you wish. If your short on cash and you can't afford to get a 8 ¾ or find the time to locate the long 8 ¾ axles for re-splining the 8 1/4 is a real nice alternative for a while and CHEAP in the yards ($50.00 non sure-grip and $125.00 sure-grip here in Texas). You may never blow up the 8 1/4 with a mild small block street car.
Castings: 2852905, 3723598, 3723599
Info: 1 5/8 pinion, 57.6" wide, 10 bolt cover, 55.6" width (flange to flange) / 51.4 housing flange to flange / 43.02 spring seat center to center.

Thank You

Russ69Runner · Jul 19, 2018

If it is a GM rear end and has been working then I would just rebuild it. Like I said you will have to look at the ring gear their should be numbers on the ring gear and a maker's mark also sometimes. Well good luck with the quest Hodgee.

jww69rrpost · Jul 20, 2018

69hemibeep said:
View attachment 26149

The rear end is not from a 68 through 70 Road Runner, and may not even be a Mopar rear end. I'd toss it and purchase the correct part. Taking it a step further, I'd go with the 8.75 489 and fill it with a Detroit Truetrac Eaton setup

Hodgee · Jul 20, 2018

jww69rrpost said:
The rear end is not from a 68 through 70 Road Runner, and may not even be a Mopar rear end. I'd toss it and purchase the correct part. Taking it a step further, I'd go with the 8.75 489 and fill it with a Detroit Truetrac Eaton setup

I would love to swap this out for a 8.75 but my resources are limited because i have only built mostly gm cars and trucks... i dont have too many leads on any mopar diffs in this area

69hemibeep · Jul 20, 2018

Process of elimination. 10 bolt chevy ID

Hodgee · Jul 21, 2018

69hemibeep said:
Process of elimination. 10 bolt chevy IDView attachment 26160

That does look like the cover but my housing doesent have the 2 bosses sticking down on the bottom corners and it has a pinion snubber bolted to the top...I have never seen that on a chevy.

RonLiv · Jul 21, 2018

What's interesting to me is there are no casting numbers. I agree it does look like a Chevy differential but there would be a casting number in the webbing area surrounding the backside of the carrier housing next to the left or right axle tube. Maybe its some kind of aftermarket thing.

RonLiv · Jul 21, 2018

Hodgee said:
I would love to swap this out for a 8.75 but my resources are limited because i have only built mostly gm cars and trucks... i dont have too many leads on any mopar diffs in this area

I saw this on another page, but there is this guy named "Mopar Mel", he's in a place called Fertile Minnesota, wherever the heck that is, and he has 4-large barns jammed full of parts and a big fenced in yard of cars. He's decided to retire. He's going to have a big auction, what ever doesn't sell he's going to scrap, but before hand if you call him he'll let you buy stuff from him apparently. But you got to make an appointment. He's not going to go look around for what you need and tell you on the phone if he has the part or not. But just given the size of the place and all the stuff, if you make a list of what you need and go up there with a truck, you could get the correct rear diff on the cheap. 218-289-1185 mel@moparmel.com / I don't know the guy, never been there, just saw this.

37586651_10156510614222334_8520542738133811200_n[1].jpg

RonLiv · Jul 21, 2018

Here's the add wording:

RETIREING.
Appointments only
Please don’t ask if I have a part

Fertile mn
Over 200 cars and parts cars 55/65....All mopars.... mostly fins parts to complete cars. Make a trip. Well worth your while make offers before the big sale you will probably get it. Bring trailers and trucks. All must go....thinking on crushing.... buildings full of parts. Here’s few

8 new engines
58 ply convert
B body converts/ parts cars
C body Hts/converts
Pickups
Dodge d-500s
57 adventure
Desoto hardtops
Imperial hardtops
Chrysler’s
Hemis
Chrysler’s converts
Dodge hardtops
Shelves- bins of parts

Rear Differential Question.

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