8.75 rear ends

[Gregr]

Good day everyone I have come across 4 complete 8.75 rear ends and from what I can tell they are late 40s-50s and I’m curious as to what they would be worth and how to identify the actual year or model vehicle they went in by using the casting number? If that possible? 
thanks

[FarmerJon]

Generally, the center section has the ratio stamped into the casting. I remember it usually being by the fill plug.

 

Axle housing widths changed at the end of the '40s, and maybe a couple times during the early '50s. Mid '50s axle spline counts changed, so while the gear set can be swapped into an earlier unit, it takes more work than just swapping in the whole center section. 

Another indicator of what make the rear came out of is brake drum diameter. Plymouth had 10" brakes. Dodge, '40s Desoto and chrysler got 11" and early '50s Desoto and Chrysler got 12".

 

As far as value, condition, ratio and year play a big roll. 

I usually see 3.90 ratio complete '40s rears on Craigslist going for around $100-150. Pulling the center section, it is worth about the same, but likely easier to sell, since it can be shipped. 

3.73 and 3.54 center sections would likely bring more.

If you are parting the axles, the 11 and 12" brakes hold some value as well.

[Sniper]

The 8 3/4 didn't come out till the late 50;s.  You might have a similar looking ale, but give us the casting numbers so we can help sort out what you have. 

 

https://www.hemmings.com/stories/article/mopar-8-3-4-inch-rear-ends

 

Info regarding earlier rear ales is slim on the internet, lol.

[kencombs]

3 hours ago, Sniper said:

The 8 3/4 didn't come out till the late 50;s.  You might have a similar looking ale, but give us the casting numbers so we can help sort out what you have. 

 

https://www.hemmings.com/stories/article/mopar-8-3-4-inch-rear-ends

 

Info regarding earlier rear ales is slim on the internet, lol.

Odd thing about that history from hemmings though, I had a 65 Dart back in the early 70s.  273/4bbl/4spd with the 66 cam upgrade.   It came with a 3.23 differential and like a lot of guys, I was looking for better acceleration.  I found a 55 Chrysler in Dad's salvage with a 3.55.  Bear in mind that the Dart had flanged axles while the 55 still had the tapered version.   Checking things over I found that the side gears in the two had different splines and the rear ujoint didn't match.   But I was able to swap the side gears from the 65 into the 55 as well as the ujoint yoke.   Only real difference was the use of an adjuster to set end play instead of shims.

 

Point being, while the 'real' 8.75 didn't appear until 57 I think, there was a lot of the earlier DNA in them.   Outside of drag strip I've never seen one broken, worn out maybe but never a catastrophic failure.

[Sniper]

Well, I have an 8 3/4 in the garage I could compare to the axle in my 51.

[kencombs]

4 hours ago, Sniper said:

Well, I have an 8 3/4 in the garage I could compare to the axle in my 51.

 

There were at least 3 maybe 4 of the 57 up differentials.   I'm sure my 65 had the A body version, but I don't know what internal differences might have been beyond the casting numbers which define the body series use.   Supposedly they are good, stronger, strongest.  Haven't ever looked at internal PNs and interchange as my Hollander doesn't go beyond mid 50s.

[Sniper]

 741,  742 and 489 are the last three casting numbers of the commonly used center sections, there are other numbers too. 

 

741 is the "weakest".

 

Stock, 742 is arguably the strongest.

 

489 uses a crush sleeve that can collapse under high HP applications causing catastrophic failure.  An inexpensive shim and spacer kit fixes that and makes it top dog of the three.

 

I know the gear carrier interchanges between them, but that's about it, for the center section anyway.  As for the casting numbers referring to what body they are in, not really, it's more of an application thing.  /6 car, likely to have a 741.  Big block automatic, 745/489.  But even that is dependent.  My 64 300 stick car had a 742, later BB stick cars usually got a Dana.

[Gregr]

I want to thank everyone for replying I will get casting numbers taken and send to you and post on this page. I’ve had rotator cuff surgery and still in recovery from that! bear with me. I will get them posted. Thanks again to all that replied.

[James_Douglas]

Actually there was an earlier 8-3/4 axle then the one we all know about in the later 1950's. It was used in the late 1930's to 1953 long wheelbase Chrysler and Desoto's as in the post war Town and Country.

 

I have one in my Desoto Suburban and three sets of gears on the bench. All have 8-3/4 inch ring gears.

 

James