Original Rear end type on my 70 Duster

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AlaskaJeff

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Is there a way to further decipher my fender tag to find out what rear end my VL29G0B Duster came with originally? It shows a D31: Light Duty 904 mated to an E44: 318 2 bbl. There are no codes that I've seen on the fender tag that denotes rear end type. So my guess is that it had a 8 1/4 rear end from the factory, is that an accurate ASSumption :D on my part? It currently has a 741 case 8 3/4 in it, but I'm pretty sure it's not original. Like the rest of the current engine/drivetrain.
 
I think the 8 3/4 would have been original, probably with the 741 case. That’s what was in my ‘71 Dart which is also a 318/904 car.

I don’t think the 8-1/4’s went into A-Bodies until ‘73, because there weren’t any SBP 8-1/4’s.
 
Most 1970 and newer v8 cars (notice I said “most”) had an 8-3/4” rear. 3:23 was a common gear ratio.
7-1/4” was another option but I believe that was /6 only by 1970.

I too agree 8-1/4” came out in 1973 to replace the 8-3/4” rear. Not sure if they ever made a small bolt pattern 8-1/4”
 
Do you have a build sheet?
Unfortunately no. Hell, It doesn't even have a BACK SEAT!!
Rear Seat Delete.jpg
 
I've seen this:
fetch?id=3661&d=1582502191.jpg

So given the previous replies and this chart, a 7 1/4 OR 8 3/4 COULD have been in the car.
 
I've seen this:
View attachment 1715923710
So given the previous replies and this chart, a 7 1/4 OR 8 3/4 COULD have been in the car.

Yes. Although in ‘70 I think a V8 would probably have gotten an 8 3/4. I don’t remember the exact year break, a 318/auto could have come with a 7 1/4 for some years but I think that stopped at some point.

But as far as I know an 8 1/4 with SBP was never available, so they wouldn’t have been in A bodies until ‘73 when the V8 cars went to BBP disks. I know the B-bodies came with them earlier than the A’s, I have a ‘71 Satellite that has a 383/727 and an 8 1/4.
 
I think the 8 3/4 would have been original, probably with the 741 case. That’s what was in my ‘71 Dart which is also a 318/904 car.

I don’t think the 8-1/4’s went into A-Bodies until ‘73, because there weren’t any SBP 8-1/4’s.
100% agreed.
There's no way an 8 1/4 would be factory installed in an A-Body in '71.
They were only available in A-Bodies starting in '73, and were big bolt pattern ONLY.
Chances are that the 8 3/4 with the 741 case in the car is original, but it also could have had a 7 1/4 too.
Back in the day, I owned a '71 Duster 318, 904, and 10'' drum brakes.
It had an 741 case 8 3/4 in it.
The car was all original except paint.
However, I currently own a '71 Demon Sizzler that is all original except the engine that is a 318, 904, and 10'' drum brake car and it has the 7 1/4 rear end in it and it hasn't been touched from new.
It doesn't make sense to me that the Sizzler would have a 7 1/4 in it seeing that it was destined to be a ''budget'' performance car....
So, it seems that at the build plant they threw in whatever was available at the build time unless the build sheet called for a heavy duty rear end ONLY...
 
Los Angeles built? On my lynch road tag it shows three 3-digit codes for which engine assy, trans assy, and rearend/brakes. 2nd or 3rd row down from the top. I don't know what might be on your tag. How about a pic? Block off the Vin if you want.
 
The 7 1/4" axle was standard on every A body built. EVERY one.
The 8 3/4" axle was the upgrade for the towing package and could be optioned even on slant six models. The 340 cars from 68-72 got the 8 3/4". All base model slant six and 318 cars got the 7 1/4" axle if there was no towing, Police or Taxi fleet option chosen.
The only reason one might be equipped with the 8 1/4" axle after 1973 was if it was optioned for it though a fleet, Police or HD towing package....or a 340/360 option.
 
GREAT info everyone. Many thanks:thankyou: My 70 was, as stated before: VL29G0B with the B for the mothership plant of Hamtramck MI. The engine code is E44: 318, D31: 904 trans but NO rear end code. I figured being it was a L code low trim model it might have had a smaller rear end. Not that it makes much difference at this point, I enjoy finding out my car's history. I've been able to track down the guy that drove it from Denver CO. to Delta Junction ALASKA in February of 2003 and the two other Alaska owners before me. It's all great conversation when people stop to chat.
 
7.25" is most likely unless it had a tow package. Have a 70 Dart 4 door 318/904 with a 7.25 in it
 
The engine code/trans code just signifies which family of part is installed, not which assy #.
For example, a 69 roadrunner engine code for a 383 would show .... 383. The assy code would tell which 383, four speed magnum, auto trans magnum, four speed with a/c, or auto with a/c. Four different 383s, four different codes on the fender tag, at least at lynch road.
Like I said, I don't have any idea what a hammtramck tag shows (oops, NOT L.A, my bad.)
 
Nobody has asked yet. Does it have factory front disc brakes?
Drums, likely 7 1/4, disc's, possibly 8 3/4.
Good question, It's a 4 wheel manual drum SBP, manual steering car.
Tag for those who want to see it.
FenderTag1.jpg
 
My bone stock 318/904 71 Twister also had the wonderful 7.25 in it.
 
Since it started life as such a low option car, I would imagine it probably had the 7 1/4 rear originally. That's my story and I'm sticking to it.
 
My 70 Duster I had in high school was a 318/904 car with factory front disc brakes, and it had a 7 1/4 in it from the factory. When you have a 7 1/4 rear end, don't do a boot leg turn in the grass and let it catch the pavement. The 7 1/4 will go KABOOMYOW! Don't ask me how I know! :eek: :BangHead:
 
I don’t think that the axle was dependent on the brakes the car was built with. I’ve owned manual front disc cars with 7 1/4” axles. One weird one was a 73 Duster 318-904-7.25 with 2.76 gears. Stripped car, too. No front sway bar, Rubber floor mats, foot pump for windshield washer, no A/C, manual steering. The title stated in capital letters: PRIOR POLICE.
I never found out what that meant.
 
I don’t think that the axle was dependent on the brakes the car was built with. I’ve owned manual front disc cars with 7 1/4” axles. One weird one was a 73 Duster 318-904-7.25 with 2.76 gears. Stripped car, too. No front sway bar, Rubber floor mats, foot pump for windshield washer, no A/C, manual steering. The title stated in capital letters: PRIOR POLICE.
I never found out what that meant.

Right, and my ‘71 Dart GT had 10” drum brakes front and rear, 318/904 and an 8 3/4. Actually I’m pretty sure both my GT’s had 8 3/4’s, both were 318/904 cars. And based on the fact that the entire driveline was stripped out of the second one, along with the buckets and console lead me to believe it had the 8 3/4. If it had a 7 1/4 I bet they’d have left it. But it was an LA plant car so no buildsheets and no other way to know.
 
Good question, It's a 4 wheel manual drum SBP, manual steering car.
Tag for those who want to see it.
View attachment 1715923762
Far out.
That car has a very late in the '70 model year scheduled build date of July 13, 1970 and a high sequential V.I.N. to go with it.
Most Dusters didn't have many options on them, yours is about typical, and it's a V8 car not the usual slant 6...
So that's a win!
 
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