My 71 Duster work in progress

Dr.Jass said:
If the axle is A-body width, the only issue should be the location of the brake-line tee. I looked through my receipts and found that the kit I ordered was for '70-'71 because of the tee location. Apparently there's a '67-'69 location, as well as a '72-only spot. If memory serves, some are right at, or even on, the center section while others are further away. I would suggest looking at the Inline Tube and/or Fine Lines website for application information; there are guys selling the IT stuff on the 'Bay for around $35 shipped... in stainless, no less.

I doubt the backing-plate differences will be much of an issue if any, since I moved my springs inboard and was still able to use the repro lines with a bit of creative tweaking. Had I gotten lines with the wrong tee location, though, I'd have been in a spot.
Click to expand...
The dr diff selector has two different tee locations to choose from., 7-3/4 and 11-1/2 from the C/L. Mine is 7-3/4.

I saw FineLines had SS lines marked down to $35 w/ free shipping over $100 or so. I need all the e-brake cables and they stock them so I will qualify for that unless I find them ridiculously cheap somewhere else.
 
See, I'm sure I ordered brake cables for my Valiant, and I'm equally sure I can't find them if I did. I'm no stranger to buying multiples of the same part but I've been trying to not do it quite so much of late. I was able to stop myself from ordering a second Challenger T/A air-cleaner "special instructions" decal the other day by looking at my last decal order. 😂
 
Also too, the axle to axle width of the rear end is 57-5/8" and the center to center on the perches is 43". The perches are A-body width but it's 1/2" wider I guess due to the difference in offset between the SBP and BBP axles.

I've got what looks to be a driveshaft for a 318 auto and one for a 340 auto, both with 8-3/4s. I guess the difference is 904 vs 727 trans. Per the FSM, 318 auto is 49.27" and the 340 is 44.99. One of mine is 49-5/8 and the other is 45-1/4 with the difference likely being my inaccurate measurement. The shorter one came in the car with the 9" rear, and is a heavier duty part than the other one.
 
Last edited:
Considering the amount of lateral movement at the slip yoke in relation to vertical deflection of the rear axle, I would think that unless you're planning on going "Duke boy"--and if you are, please film it--you'll be fine with a scant 0.26" of extra length.

The slip yokes between the two should be different: The A727 has a larger, 30-spline output (shared with most iron-case A833s) than the 26-spline A904 (shared with 3-speeds, early A-body A833, and late A/F aluminum A833OD).
 
I didn't think to compare the yokes.

I cut/ground the bars off the shock plates. It took about half of forever because I was using a body saw trying to not throw fire and metal dust all over my garage. I found some Milwaukee "Torch" sawzall blades and tried that, but it only took a couple of times of it kicking back on me before I decided to switch back. I gave up on the body saw on the second one and broke out a 3" air whizzer.

One shock mount does look to be bent compared to the other, but it's good enough to use. Danged air shocks.

I put all the e-brake parts in sans the cable and was bummed about what a fight it was. I used to do brake jobs for a living, so it was pretty sad. I think part of it was caused by the rear floating around on the trans jack, similar to what you mentioned eaflier.. It should be easier once it's bolted in. I'm hoping I can take one spring off each and pry the bottom apart to get the cable hooked up with the shoes mostly installed.
 
I much prefer the angle grinder for such nonsense, so I have a backing plate I use when I have to grind something on the floor or in the vise. Another old PC side panel--those things are damned handy*--with a former car-audio 6x9 speaker magnet I stick to the back of it. The panel blocks the sparks, and the magnetized area catches and holds the metal shavings. After a brief but important cool-down, put the panel over the garbage can (or scrap bin if you've got one), pull off the mag-a-net, and the metal harmlessly falls where it belongs. Some metal will invariably kick back, but once you find the glory spot for the backstop, it's surprisingly little.

*I should probably do a thread on the multiple uses I've found for those things. Ones from before/right around the turn of the century are the best... very sturdy.
 
I installed the rear yesterday. I just rolled it under the car on the trans jack, raised it over the spring height, then bolted up the shackles and dropped it down on the springs.

It's great fun pulling 125 ft/lbs on the spring eye bolt, while sitting on the ground. Leverage is your friend and I had little to none.

I put the tires on it and set it on the ground, and the transmission plug that hadn't leaked a drop let a quart or more of ATF out. Just another mess to clean up before I can do anything else. I was just about to type that I need to take the yoke off one of these old driveshafts and use that instead - and realized there is a slip yoke in the 4-speed that came with the car. Oh well, maybe I'll remember next time but I wouldn't bet on it.

IMG_2541.JPG

Tires aren't on the ground but the weight's on the axle. I don't know what springs are under the thing but they're stiff. I think they're just standard Duster springs with added leaves. It had 7 in the front section.
IMG_2585.JPG
Notice the orbs too 👻👻👻👻👻
 
I made a trip to NAPA to get the rear brake hose and u-joint straps. The counter lady was talking to another customer about some medical procedure gone wrong- something about they worked on the wrong leg. Yikes.

Today's job here is to get the fitting on the end of the brake hardline to turn so I can connect the hose between there and the brass block on the rear end. Hopefully I can keep it from twisting the end of the line off. I had to turn the rubber hose (unconnected on the other end) off to get it apart, so it's pretty well stuck.

I might get an idea on what I need for a driveshaft too - and at least replace that plug with the spare slip joint.
 
It never ends. We asked for a 7290 yoke, guess what?

There was no upcharge and I'm not looking forward to pulling the yoke off the rearend, so I'm not sure what recourse I have at this point.

The driveshafts are both 7260 so the 7290 was more of a planning for the future thing. I'm glad I didn't rush out and have a driveshaft made, but even then I could've used an adapter joint, backward.

It's just a street car too, so it's never going to dead hook and cause any worry about breaking anything.

FWIW I did check that the gear is what we asked for before I stuck the thing under the car. There was an upcharge to go from 3.23 to 3.91.
 
To make the most of what you've got, I'd suggest using Spicer's "Life Series" 5-789X U-joints, which are non-greasable 7260 joints. They're much stronger than their greasable brethren, and that grease ain't coming out--nor is anything going to enter. I have the 7290 version of same in the Valiant's driveshaft, which (hopefully) will dead hook on a 4,000RPM leave--with a stick. The guys that built my propshaft (Machine Service) said going to a larger joint like a 1350 wouldn't be necessary with the Spicer Life parts.

Multiple driveline guys, including Machine Service and Gabe from Northern Drivetrain have recommended them above anything else; the latter's got a pretty funny story about his (unsuccessful) attempt to convert a Spicer Life into a greasable joint. Gabe's a pretty serious off-roader/rock crawler, and he swears by 'em. The former makes their own U-joints, but for my project said I absolutely wanted the non-greasable Spicers. I don't want mechanical fuses.
 
I bought Moog 246, which is drilled for a zerk in the cap so it's stronger. There's a bunch of other goobledygook in the info intended to help me understand why they're stronger.

The shaft that came out of the car originally with the 9" rear has about 1-1/2" between the cap and the yoke with the shaft shoved all the way in the transmission, so I'm going to go with that one. The rear end is so stiff there's hardly any travel in it, and once I put the snubber on it should enforce that.
 
b-body-bob said:
I bought Moog 246, which is drilled for a zerk in the cap so it's stronger. There's a bunch of other goobledygook in the info intended to help me understand why they're stronger.
Click to expand...

It's certainly stronger than their standard part for that application, the 315G. Ten or fifteen years ago, I'd have sold you that joint confidently. Rather than go into the long, convoluted story about rebranding and reputation, suffice to say Moog does not, nor did they ever, make U-joints (or hub assemblies, or anything but chassis parts). Back when the U-joints were Precision and the hubs were National, they were solid parts. Now it's a miracle if the stuff fits, never mind actually lasts. Thanks, Federal-Mogul!

b-body-bob said:
The shaft that came out of the car originally with the 9" rear has about 1-1/2" between the cap and the yoke with the shaft shoved all the way in the transmission, so I'm going to go with that one. The rear end is so stiff there's hardly any travel in it, and once I put the snubber on it should enforce that.
Click to expand...

Do you mean the U-joint cap on the driveshaft with the latter bolted to the rear? If so, that sounds pretty close. I believe the measurement is supposed to be taken with the yoke's base approximately ½" out from the transmission seal's dust boot (don't quote me on that) but it's usually easily seen by looking at the rust line on an untouched original yoke. I literally used an old yoke's rust line to make my measurements.
 
Dr.Jass said:
Do you mean the U-joint cap on the driveshaft with the latter bolted to the rear? If so, that sounds pretty close. I believe the measurement is supposed to be taken with the yoke's base approximately ½" out from the transmission seal's dust boot (don't quote me on that) but it's usually easily seen by looking at the rust line on an untouched original yoke. I literally used an old yoke's rust line to make my measurements.
Click to expand...

I shoved the driveshaft all the way in and measured between the back of the cap and where it mates with the yoke.
 
Still thinking about the driveshaft length.

Per the FSM an A-body with 340 727 8.75 has a 44.99" driveshaft. My driveshaft measured roughly 45-1/4. The transmission mount is in the typical A-body position, and from what I've seen all car transmissions use the same tail shaft. So my driveshaft is at worst 1/4" too long compared to the factory spec.

Also noted that a Dart 340 727 8.75 has a 45.25" driveshaft. The part I have could be a Dodge part.

We're really good at getting lost in the weeds on these things :D
 
Last edited:
OK, the FSM situation you posted sent me scampering into the parts book. There's a 3" difference in wheelbases; a .26"-longer driveshaft would not work.

Per the '70-'72 parts books, early in the listings the V and L (Valiant and Dart) models use the same length driveshaft, which makes zero sense considering the V's 108" wheelbase and the L's 111" wheelbase. It's only further down the listings that we see the 340/727 Dart as actually having a 47.99" shaft--exactly 3" longer than the Duster/Valiant as would be expected. Stranger yet, the VH (I'm guessing Duster) is not listed as available with a 340/727 combo in the '70-'71 book. A230 or A833 are the only transmissions listed. Even more confusingly, the A904 and A727 are shown as using the same driveshaft. The '72 book is clearer, but only just... they at least list 340/727 combinations, and did away with the VH nonsense (which makes no difference) entirely. There is no 45.25" driveshaft listed in the parts books '70-'72... the closest is the 7290 shaft for a A727/A833 Challenger, which is 45.60" (the 7260-joint shaft is 45.79"). Challengers have a 110" wheelbase. Yes, it's 1" shorter than a Dart and 2" longer than the Barracuda, which was 108" like the Duster.

Fun stuff. It got even more fun a year or two later when they started building 111" Valiant models while keeping some 108" models around.

Ultimately, it's about the transmission. All the transmissions use the same distance block flange to trans mount pad, so a V body style with an A727 is all that matters. Darts, for the moment, can f__k right off. Your shaft, with 7260 joints and all the driveline parts in the OE location, should be 44.99" long. With the driveshaft assembled and installed in the rear axle, there should be a gap between the output seal's dust boot and the yoke, at least half an inch (meaning the yoke is approximately 1.5" from the output seal's flange). The distance may be greater; I find as I'm aging all these number in my head are starting to dance a bit, sometimes "field" numbers v. FSM numbers, etc.

Experience has taught me the .26" will not affect you. The C/L to pinion yoke distance is longer on an 8¾" axle than it is on an 8¼" axle, but many such swaps have been happily done with the same driveshaft and run well for many years that way, including the '82 Mirada that got such a swap in my garage almost two decades ago... on New Year's Weekend, no less.
 
Good point, I wrote Dart then thought should've done Demon but didn't change it. It sure seems like it oughta be OK. FWIW I also found info from people that should know, saying to shove the slip joint in until it bottoms, measure C-T-C back to the yoke, then subtract an inch for the right length.

I'm going to take a little time to check the driveshaft angle, since the motor's on a plate the output shaft angle could've changed, and there's no guarantee what angle the perches are at.

I've been busy today clearing out space to put the two apart-but-complete BB engines and the K-frame spindles etc that we still need to get out of the lady's garage. We didn't get any photos of that but I'm hoping for big ball joint parts and a spool-type motor mount. But I also know how my luck runs so I'm expecting worn out junk and a /6 k-frame. It would be good to dig in and find the E-brake handle in her mess of stuff too.
 
b-body-bob said:
It sure seems like it oughta be OK. FWIW I also found info from people that should know, saying to shove the slip joint in until it bottoms, measure C-T-C back to the yoke, then subtract an inch for the right length.
Click to expand...
I may be wrong here, but I'm pretty sure they mean "bottoms against the boot" and not in the trans or inside of the yoke. But, to be sure, I'd have the tape @ 45" exactly, and measure from the rear yoke with its ears horizontally oriented. See where that puts the front yoke.

Also, I mentioned it previously, but this should be done with the car level, supporting its own weight on the suspension, with the entire drivetrain installed. I'm pretty sure that's what you're doing, but it bears mentioning to anyone reading this a few years from now. Yes, installing the engine does compress the rear suspension!

Having done the level of cutting on these cars that apparently you and I (and Stretch) have done, and no doubt restoman, it's shocking how we'll still competely overthink this stuff. Resto seems to have the best grip on it; I should after installing a frame rail and noticing the factory'stolerance (+/- .250"!) for the K-frame mounting bolt hole measurement from the rear. Precision assemblies, they ain't.
 
I agree, there's a whole lot of "yeah that's good enough" when it comes to cars and I tend to overthink things.

I measured the shaft again yesterday and it's right at 45-1/4" C-T-C. Also at least this one post is explicit

https://www.forabodiesonly.com/mopar/threads/pinion-angle-and-driveshaft-length.229290/#post-1970010790
3. Slide the slip yoke forward until it bottoms out inside the transmission
4. Measure from the center of the front U-joint to the center of the rear U-joint.
5. Subtract 3/4" to 1" to compensate for slip yoke travel. This is the ideal driveshaft length
Click to expand...

I also tried to check the angles and using the angle finder I have (hard to read) the trans is up 1* and the diff is down 5*. I didn't notice if there are any shims under the trans or not. I might need to shim the perches to correct that. I'm going to pick up a digital angle finder first though, so I can read the angles accurately.

The front wheels are on the ground, with stands under the rear axle. The tank is empty and there are no bumpers or fenders and grille on the car. That shouldn't influence the difference between angles even though the measured angles aren't the true angles. I should probably wait until it's together to check the angles, but at that point I could just drive it and see if it vibrates, and adjust if needed.
 
ive cut em pretty good too doc....remember the roof swap on that 69 fastback?...or straightening my bent 69.5...and of course taking a 68s rails and stuffing them under a 71 dodge truck

overthinking when it comes to frame stuff is NEVER a bad thing...it keeps you out of trouble later

honestly i wouldnt stress the drive line angles much....when you start considering things like suspension travel max outs and such..run the HD u-joints and youll be fine....
 
You must log in or register to reply here.

SiteLock

SiteLock
Back
Top