Driveshaft Upgrade - What do I need
#1668689
09/07/14 10:47 PM
09/07/14 10:47 PM
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Joined: Jan 2003
Posts: 1,482
Lake Orion, MI
goldduster318
OP
pro stock
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OP
pro stock
Joined: Jan 2003
Posts: 1,482
Lake Orion, MI
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I have a 1970 Duster with a 340 4-speed and an 8 3/4. Engine made 470hp and 455 lb-ft. I currently have a stock driveshaft that's about 2 1/2" diameter with the 7260 U-joints. This factory driveshaft seems to have some jump-rope effect going on, and also makes me a bit nervous with this amount of power.
I see that there are a lot of options out there. At what power level would you need chromemoly tubing, forged weld yokes, etc. Please make a recommendation. I would like to go for 1350 U-joints.
Also, it seems that I always have to measure the driveshafts- you'd think the measurements for this application would already be available...
'70 Duster 470hp 340/T56 Magnum/8 3/4 3.23 Sure-Grip
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Re: Driveshaft Upgrade - What do I need
[Re: goldduster318]
#1668690
09/07/14 10:59 PM
09/07/14 10:59 PM
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Joined: Dec 2004
Posts: 10,554
Rittman Ohio
fourgearsavoy
I Live Here
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I Live Here
Joined: Dec 2004
Posts: 10,554
Rittman Ohio
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If I were having a new shaft made I wouldn't do anything less than 1350 joints  Plenty of room to grow in the future and you have more joint than you need for now. Gus 
64 Plymouth Savoy
493 Indy EZ's by Nick at Compu-Flow
5-Speed Richmond faceplate Liberty box
Dana 60
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Re: Driveshaft Upgrade - What do I need
[Re: 71yelladustr]
#1668692
09/07/14 11:36 PM
09/07/14 11:36 PM
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Joined: Jan 2003
Posts: 1,482
Lake Orion, MI
goldduster318
OP
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OP
pro stock
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Lake Orion, MI
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Yep - 1350's it is.
What about the material for the tube and weld yokes?
'70 Duster 470hp 340/T56 Magnum/8 3/4 3.23 Sure-Grip
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Re: Driveshaft Upgrade - What do I need
[Re: goldduster318]
#1668694
09/08/14 01:58 AM
09/08/14 01:58 AM
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Joined: Mar 2007
Posts: 3,277
West Coast, USA
jbc426
master
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master
Joined: Mar 2007
Posts: 3,277
West Coast, USA
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Strange Engineering has a heck of a deal on custom drive shafts with forged ends and the rest of the parts.
I'm calling Dr Diff and he'll have the stuff drop shipped from them. I like hearing his advice and rely on his wisdom regarding drivelines, plus he's great to deal with.
1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's
1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)
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Re: Driveshaft Upgrade - What do I need
[Re: DoctorDiff]
#1668696
09/08/14 09:21 PM
09/08/14 09:21 PM
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Joined: Jan 2003
Posts: 1,482
Lake Orion, MI
goldduster318
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OP
pro stock
Joined: Jan 2003
Posts: 1,482
Lake Orion, MI
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Seems reasonable.
Now with the measuring part. I'd have to measure for the driveshaft with a 7260 yoke installed when I'd really be using a 1350 yoke. Will this throw it off? It's not easy to get under the car at ride height. Guess I'll throw some jackstands under the rear axle.
I just can't believe that there isn't a known measurement for a 108" WB A-body with an A-833 (or 904 for that matter).
'70 Duster 470hp 340/T56 Magnum/8 3/4 3.23 Sure-Grip
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Re: Driveshaft Upgrade - What do I need
[Re: goldduster318]
#1668697
09/08/14 09:26 PM
09/08/14 09:26 PM
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Joined: Dec 2003
Posts: 22,696
Bitopia
jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,696
Bitopia
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A 340 at 470 hp and an 8.75 and considering 1350's IMO is a good candidate for an ALUM DS.
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
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Re: Driveshaft Upgrade - What do I need
[Re: goldduster318]
#1668698
09/08/14 10:40 PM
09/08/14 10:40 PM
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Joined: Aug 2011
Posts: 1,028
NB, Canada
moparfan53
super stock
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super stock
Joined: Aug 2011
Posts: 1,028
NB, Canada
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Quote:
Seems reasonable.
Now with the measuring part. I'd have to measure for the driveshaft with a 7260 yoke installed when I'd really be using a 1350 yoke. Will this throw it off? It's not easy to get under the car at ride height. Guess I'll throw some jackstands under the rear axle.
I just can't believe that there isn't a known measurement for a 108" WB A-body with an A-833 (or 904 for that matter).
There is a known measurement (assuming you mean the original/factory length), the Chrysler parts book as well as the FSM has that info. When I get home I will post the length if nobody else has by then.
There used to be a chart in the tech archives here on Moparts. I took a quick look but did not see it.
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Re: Driveshaft Upgrade - What do I need
[Re: goldduster318]
#1668699
09/08/14 11:37 PM
09/08/14 11:37 PM
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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I'd find out if the 1350 and the 7260 front yokes are the same (for distance) & if not then I'd get it in hand (or borrow one) & install it with the front and rear (axle) up on stands (vehicle fairly level) & butt the yoke all the way in the trans & get an exact C to C distance then subtract 3/4-7/8" from that dimention but go with what Doc says, he's the man but (just me) I would not go with a "known A body shaft measurement"
live every 24 hour block of time like it's your last day on earth
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Re: Driveshaft Upgrade - What do I need
[Re: DoctorDiff]
#1668702
09/09/14 03:00 AM
09/09/14 03:00 AM
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Joined: Jan 2003
Posts: 27,421
Balt. Md
383man
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,421
Balt. Md
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If I did not have the right yoke I usually borrowed one as I always measured any cars driveshaft I was having made even if I had what the readings were supposed to be. Always do a center to center reading and have the shaft made the right size the first time.  Ron
Last edited by 383man; 09/09/14 03:01 AM.
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on the 1350 joints especially with a stick. Then you can put a set of slicks on and test out your 8 3/4. 
