What Differential Do You Have in Your 1965 Barracuda?

[dibbons]

Don't know for sure what it had from the factory, but a previous owner installed an 8 3/4 open rear end (489 case) in my '65 Formula S automatic. (did you notice the big dent in the lower part of the center rear?).

 

[Keith Mopar]

That’s what I’m running behind a 360 magnum crate motor with 3:23’s.
I believe the 273 4barrel motors received 8 3/4 diffs under warranty if they blew up the 7 1/4.

 

[dibbons]

I wonder if mine is a warranty differential, never considered that before?

 

[toolmanmike]

I wonder if mine is a warranty differential, never considered that before?

Yes. 7 1/4 was stock. If you blew it out (with the Charger/Commando engine) you got a 8 3/4. Or so I've heard

 

[RustyRatRod]

I THOUGHT 65 was the first year for the 8 3/4, BUT it would have been the 741 center, not the 489. Mike, did they not make it in those until 66?

 

[toolmanmike]

I THOUGHT 65 was the first year for the 8 3/4, BUT it would have been the 741 center, not the 489. Mike, did they not make it in those until 66?

741 and 742 came first. 741 cases were used in the A bodies and 742 in the B bodies.

 

[RustyRatRod]

741 and 742 came first. 741 cases were used in the A bodies and 742 in the B bodies.

Yeah, I knew that part. I guess I shouldda been clearer than mud. lol I was askin what year the 8 3/4 came in the A body first? I caint remember.

 

[toolmanmike]

Yeah, I knew that part. I guess I shouldda been clearer than mud. lol I was askin what year the 8 3/4 came in the A body first? I caint remember.

66 in production

 

[ch1ll]

I believe that is not the original rear axle, I believe it would have a 741 or 742 center section.

 

[69FBCuda]

8.75 w/ 741

 

[azaustin]

This is good information, but I have a question. Would a build sheet or anything else indicate if a ’65 A body came with an 8.75? I guess I’m wondering if you put the correct 8.75 in a ‘65, would it technically be correct? My Dart GT was built late in the model year, but it had a 7.25 when I got it. It’s an original 235hp 4-speed car.

 

[33IMP]

This is good information, but I have a question. Would a build sheet or anything else indicate if a ’65 A body came with an 8.75? I guess I’m wondering if you put the correct 8.75 in a ‘65, would it technically be correct? My Dart GT was built late in the model year, but it had a 7.25 when I got it. It’s an original 235hp 4-speed car.

I am not positive.... but! I would assume that since a build sheet is an assembly guideline, it should certainly tell what rearend to put in the car.

 

[cosgig]

Yeah, I knew that part. I guess I shouldda been clearer than mud. lol I was askin what year the 8 3/4 came in the A body first? I caint remember.

The 8 3/4” was available by late 1965, although always as an extra cost option. Mopars big fix for the weakness was to make the 7 1/4” Suregrip standard on the 4bbl cars. I would bet that under warranty, the 8 3/4” was not the first repair, it was probably given to repeat “offenders”, after a couple times into the dealership.

 

[toolmanmike]

This is good information, but I have a question. Would a build sheet or anything else indicate if a ’65 A body came with an 8.75? I guess I’m wondering if you put the correct 8.75 in a ‘65, would it technically be correct? My Dart GT was built late in the model year, but it had a 7.25 when I got it. It’s an original 235hp 4-speed car.

It should show on the build sheet.

 

[65dartcharger]

8 3/4 axle was optional from April/May of 1965.

 

[Kern Dog]

You could get the 8 3/4 in later models if you had the HD towing option group. It also came with a bigger radiator, fan shroud and in some cases, front disc brakes.

 

[cosgig]

You could get the 8 3/4 in later models if you had the HD towing option group. It also came with a bigger radiator, fan shroud and in some cases, front disc brakes.

I was only speaking to the early A bodies, as he asked about a 65. Although you speak the truth. In 67 the 8 3/4” was standard with the 383 in a Barracuda, in 68 it was standard with all 340 and big block cars, and remained standard throughout the next few years until 1973 when it was replaced by the 8 1/4”.

 

[YY1]

Actually 741 was used in 66 B body cars as well.

742 was an interim design from about 1969 to IIRC early 1970.

Then the 489 came in.

WAY more 742 and 489 cases made than 742.

 

[cosgig]

Actually 741 was used in 66 B body cars as well.

742 was an interim design from about 1969 to IIRC early 1970.

Then the 489 came in.

WAY more 742 and 489 cases made than 742.

The 742 was available as early as the 67 model year, and was phased out in 69 when the 489 was implemented. Although it’s funny, the “657” cases of 1964 were the same size as the 741, and they came in all Max Wedge and Hemi cars, and although the 741 gets a bad name for being the “small” rearend, somehow they managed to survive 100’s of neutral drops.

 

[YY1]

I'm claiming "closest to the pin" on my memory banks.

They definitely changed application parameters in 67.

Every V8 1966 B body I've ever owned has had a 741 case 8 3/4.

The only 67 I've ever had with an 8 3/4 is my wagon, all others (318 cars) have had a 7 1/4.

Now I want to see what case is under that unmolested wagon.

 

[toolmanmike]

This discussion is something there is no definitive answer for. If your 65 was built with a HP273 you "probably" got a 7 1/4. I haven't seen anything that stated that after X date or X VIN the cars got a 8 3/4. If your 65 has one, there is a chance it was replaced at the dealer. THere could be a slim chance (very slim) that it left the factory with one possibly very late in the production year. The Build sheet "should" tell. THe fender tag will not.

Speaking of which, the rear axle sales codes are from 371-379 and all that is listed is ratios and not rear axle models. That includes all cars. Sure grip is a 592 option.

 

[barbee6043]

The 8 3/4” was available by late 1965, although always as an extra cost option. Mopars big fix for the weakness was to make the 7 1/4” Suregrip standard on the 4bbl cars. I would bet that under warranty, the 8 3/4” was not the first repair, it was probably given to repeat “offenders”, after a couple times into the dealership.

A few years ago I had what I thought was an original 65 Cuda 273 4 bbl car. It had a 7 1/4 with sure grip 10 in drums. Who knows if original rear end. But if the original rear end out, Ron Slobes yard was just down the road and 7 1/4 A rears with sure grip and 10 in drums were heap.

 

[4mulas]

I had one of the very first 1966 production formula S car’s, number 00521 of the assembly line built in September of 1965, and it came with a suregrip 3.23 ratio 7 1/4" diff. I Think that it could have come with a 8.75 if a box was ticked or if they weren’t trying to use up 7.25 sure grip units.

most of if not all later production S cars for the 66 year received 8.75" units

 

[toolmanmike]

I had one of the very first 1966 production formula S car’s, number 00521 of the assembly line built in September of 1965, and it came with a suregrip 3.23 ratio 7 1/4" diff. I Think that it could have come with a 8.75 if a box was ticked or if they weren’t trying to use up 7.25 sure grip units.

most of if not all later production S cars for the 66 year received 8.75" units

Interesting. They were probably using up old inventory. LOL

 

[toolmanmike]

The Hamtramck site has some good info. Here's from a spec sheet for Valiants in 1965. It lists the 7 1/4 as a standard rear and the 8 3/4 as optional.