Rear end options.

What rearend option.

  • Go for the ford 9 inch

    Votes: 5 9.1%

  • Go for the 8 3/4.

    Votes: 33 60.0%

  • Rebuild the 8 1/4 guts.

    Votes: 15 27.3%

  • Other option.

    Votes: 2 3.6%
  • Total voters
    55
  • Poll closed .
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Cuprum-74

Cuprum-74

Moparus Fanaticus
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Hey all, here is my dilemma.
I have a 1974 Duster with a hopped up 360 pushing around 375-385hp range at the crank.
With a A999 transmission converted to non-lockup with a cheetah valvebody.
I currently have an 8 1/4 suregrip rear that is well worn and noisy. I changed out all the bearings but come to find out I think the clutch in the carrier is giving too much, it almost acts like an open diff. It has about 200,000 miles on it.

I stalked a local salvage yard that specializes in classic cars.
I've done some research regarding Chryco 8 3/4 rears and Ford 9 inch. I know I need 43 inches for the perches.

I found some B-body and one early A-body 8 3/4 axle. All the spring perches measured 44 inches.

I found a few ford 9 inch axles as well. A few of them measured 43 inches at the perches. One out of a 60's mustang, a few falcons and a I think a comet.
He wants $300 for either the 9 inch or 8 3/4 axles complete. I want keep the process as simple and budget minded as possible (under $800)

Now the question is do I go for the 9 inch, 8 3/4, find a new or (if possible) rebuild the 8 1/4 carrier.
Open to other options as well.

And another thing, all the rear-ends in the salvage yard are one-leggers. There were no sure-grips or trak-loks or whatever.

*Edit: I did find one chrysler (300?) car that looked like it had a Dana 60 one-legger.
 
IF the B body 8.75 is early enough get it
Reweld the perches and your done ...will even bring the wheels out an inch or so per side
 
diymirage said:
IF the B body 8.75 is early enough get it
Reweld the perches and your done ...will even bring the wheels out an inch or so per side
Click to expand...

I'd probably pass if the 8.75 is 64 or earlier due to the funky axle nut and needing a special puller to pull the brake drums
 
I think it's a toss up between the 9" & 83/4". The 9" is much more popular and therefore parts are easier and less expensive. Your budget is a little low but doable. Some 9" pfford trucks and Broncos have 3.70 r & p. FYI
 
Admit that you are in over your skill level, and get a professional to rebuild the 8 1/4. Any swap you are considering is far more effort and expense than you imagine. Besides the obvious needs of the proper width overall and for perches, you will need another driveshaft and some devilish fabrication of a parking-brake mechanism compatible with a different axle. Plus a proportioning valve to get brakes approximately balanced front-rear. The price of another axle and diff (and brakes) will well exceed any repair bill on the 8 1/4, and your work is just beginning.
 
People sure do like to spend your money, don't they? Fix the 8.250 up. It is plenty strong, bolts in right with no modifications and has plenty of aftermarket support for gears. It's a no brainer.
 
I'm with Rob, on this one. You ever hear the song "Love the one Your With".Keep your 8 1/4 fix it. With $800 to spend you will money left over.
 
Dana 35's are dirt cheap to score parts from, most have a track lock and you can also use the disk brakes from the Cherokees for 2-350 or so just change the bearings out and you are good, inspect the friction plates out also if new is needed they are around 80 or so. I have a 8 1/4 behind a 440 and it is plenty strong. I am with Rob keep it! I get them all the time and find 3.55, 3.73 and 4.11 gears that can swap all the time and the bonus is you can get the rear disks for it for almost nothing to fit the 8 1/4 I did a thread on it a while ago.
 
8 3/4 all day long been beating on them for years NEVER broke one.
 
65 Dartman said:
I'd probably pass if the 8.75 is 64 or earlier due to the funky axle nut and needing a special puller to pull the brake drums
Click to expand...
That was the case through '65 at least. And, if you find what has a 741 carrier in an 8-3/4" housing from an '62-'65 B with a /6, it will actually have an oddball 8-1/4" R&P, that was used only in those 4 years.

I think I would just rebuild the 8-1/4" if I were keeping the car and on a budget. For the much higehr $$ for the 8-3/4" path, it will add some resale value if the car is going to be sold anytime.
 
RustyRatRod said:
People sure do like to spend your money, don't they? Fix the 8.250 up. It is plenty strong, bolts in right with no modifications and has plenty of aftermarket support for gears. It's a no brainer.
Click to expand...

I agree, the more expensive and complicated the more likely most of these guys cars will sit up on blocks instead of out driving and having fun.

But if you do a lot of long trips the 8 3/4 has one advantage is easy gear swaps. My uncle had a pretty serious 340 duster back in the day but when we would go on camping trips he'd put in some 2.94 gears and tow the boat or the camper up north (340 don't make torque lol).
Most of the time it had 3.23 in but if he felt like racing he'd drop the the 4.10 and go looking for cars to beat.

P.S. his car is on blocks now lol didn't survive the last 340 build he was shooting for 500 hp but never got put back together.
 
on a side note, if hes asking 300 for the whole rear end why not buy two, install one and offer the other here for 600 ?

or at least see if hes got a suregrip unit you can get me ;)


oh, and as far as installation expenses...when I went from a 7.25 to a 8.75 I was able to use my stock parking brake cable
 
Contrary to common opinion, Cone-type suregrips are/can be, rebuildable. Easy-peasy. Just cut .060 to .080 off the cones and install a appropriately sized hardened washer between the cones and the side gears. I tighten the backlash up until it starts to turn funny, then back-off to the next thinner washer, to allow oil clearance.I use Ford side gear washers cuz my local ford dealer keeps 'em in stock. For street I set them up with about 120 ftlbs of turning torque with EP oil liberally coating the guts. Too much more and they squeal a tire at every corner, unless you are running at least 275s. Under a 100pounds, they begin to slip, and I get a do-over.I hate do-overs.
If the cross-pin holes are egged out, I have had a local machine shop weld them up and re-machine them, with good success; However, it ain't cheap.If it needs both jobs performed, I would recommend a good pick-a-part. You will be money ahead.
On the street that 8.25 with a tight set of differential gears and street tires,can take a pretty good licking, even with 275s or better.The trouble starts when the SG dies, and you start peg-legging it.
 
Ok, now the bigger question is: is the 8.25 SG even rebuildable? I mean the carrier unit itself, is it even worth the hassle? Especially since my SG almost acts likes an open diff.

I'm going to the local Six States here and get a quote for the 8.25.
 
Tantibus-74 said:
Ok, now the bigger question is: is the 8.25 SG even rebuildable? I mean the carrier unit itself, is it even worth the hassle? Especially since my SG almost acts likes an open diff.

I'm going to the local Six States here and get a quote for the 8.25.
Click to expand...

Get some new clutch plates, Dr diff has them I think around 85 or so, easy to put in.
 
RustyRatRod said:
People sure do like to spend your money, don't they? Fix the 8.250 up. It is plenty strong, bolts in right with no modifications and has plenty of aftermarket support for gears. It's a no brainer.
Click to expand...

With Robert,on this one. Keep it simple & bolt in,save your balonies for better uses.
 
RustyRatRod said:
People sure do like to spend your money, don't they? Fix the 8.250 up. It is plenty strong, bolts in right with no modifications and has plenty of aftermarket support for gears. It's a no brainer.
Click to expand...

Below is a copied reply from another thread recently started. I'd like to add this comment up front. 8-1/4 suregrips are available new at very reasonable prices.

MRGTX said:
I appreciate that but I've consistently been steered away from 8.25" due to the C-clips, availability of components, etc...also, they're not as stout as an 8.75, no? I'm thinking that slicks might spell the end of one of those.
Click to expand...

The 8-1/4 gets a bad rap due to the size and C-clips. While C-clips can fail, it is when there under abuse there limitations arise. If the car is going to spend a lot of time with slicks and at the track, something larger may be a good move. Normal and occasional spirited driving is fine.
I have not noticed a shortage of components or selection of ratios. These rear can hold 400HP all day long. While the 8-3/4 is a much more stout part, the price is reflected.

No matter what rear you use, there is something some one could point at as a short coming.
What is the intended power level?huh
 
rumblefish360 said:
Below is a copied reply from another thread recently started. I'd like to add this comment up front. 8-1/4 suregrips are available new at very reasonable prices.



The 8-1/4 gets a bad rap due to the size and C-clips. While C-clips can fail, it is when there under abuse there limitations arise. If the car is going to spend a lot of time with slicks and at the track, something larger may be a good move. Normal and occasional spirited driving is fine.
I have not noticed a shortage of components or selection of ratios. These rear can hold 400HP all day long. While the 8-3/4 is a much more stout part, the price is reflected.

No matter what rear you use, there is something some one could point at as a short coming.
What is the intended power level?huh
Click to expand...
Right now I'm pushing mid to high 300 hp at the crank. Eventually I'll be getting better aluminum heads. I currently have slightly worked over cast 308 heads.
My goal is to eventually get around 400+ hp, at the crank or 300+ at the wheels. (assuming a 25% drivetrain loss)
 
Not that Rusty needs any help here but there have been plenty of pics of hurt 8.75 pumpkins and gears that took a serious hit. The stock cap bolts and caps seem to be the weak link along with the cheaper sets of gears. I trashed a set of 4.88s back in the 80s and then in the 90s I peeled the splines off of a factory axle in my 70 Cuda. I should have had aftermarket axles in a big block car with 5.13 gears and 13-33W slicks...
 
Well, I've kind of decided against the polls a little. Due to budget reasons only, I contacted Dr.Diff (Cass Eslick) And got a Suregrip clutch pack rebuild set for $65 ($81 after shipping).
And have access to a buddies shop with a lift and specialized tools.
That said and done I can get this rearend serviced for less than $100 if I don't need new ring & pinion gears.
If I do need new R&P gears that's only around $160-$200, still way under the $800 budget. (save the rest for Christmas shopping).

Ok another question: I did see an old 1966? Plymouth Belvedere 4 door (what I thought was a Chrysler 300 until I got a closer look) in the local salvage yard that had a Dana 60 one legger in it. Still he wants $300 for the whole axle only.
Is this thing worth even getting? (not now, but possibly later)
Still has the 440 in it too... Hmmm... Very tempting.
 
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