U Bolts from a Dakota rear end working on an 8 3/4. Has anyone used this or heard of this.

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mjmayhem

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I believe I saw this on Slant six.org a while back. Has anyone used the Dakota rear axle U bolts on an 8 3/4 rear end? They supposedly have the flat spots at the top of the u bolt
for proper alignment of the axle.
 
I believe I saw this on Slant six.org a while back. Has anyone used the Dakota rear axle U bolts on an 8 3/4 rear end? They supposedly have the flat spots at the top of the u bolt
for proper alignment of the axle.
U-bolts don't care what they are on... if the axle is 3" diameter and the right length the ubolts will work... I bought new ones from mancini with the flat spot also.
 
That's not possible.. I wonder if you can go to the parts house and use universal ubolts in place.. Now if those fit report back with your finding's you sir are a genius.
 
Thank you Icetech for the advice on Macini Racing .I see they have the proper ones with the flat spot at the top of the u bolt. Thanks again.
 
Thank you Icetech for the advice on Macini Racing .I see they have the proper ones with the flat spot at the top of the u bolt. Thanks again.
No problem, i also didn't want the round ones, don't like the dent they leave..
 
That's not possible.. I wonder if you can go to the parts house and use universal ubolts in place.. Now if those fit report back with your finding's you sir are a genius.
They say the universal u bolts are round at the op where the bolt contacts the top of the axle tube. This will crush in the tube. That is why it is important to have the right u bolts. From what I have read.
 
As long as the Dak has a 8 1/4 or 9 1/4 rear, there's no reason they shouldn't work. Like Icetech said- the bolts don't care what they came off of, just so the tube diameter is correct. Just may be a little long, especially if coming off a 4x4. Beware the 4 cyl. Daks, they had 7 1/4 rears and the wrong axle tube diameter.
 
What's "proper"? Flat insides around the bend because you think it is "proper"? I've torn down a LOT of original suspension Mopars and not one single one ever had the flats around the inside of the u bolt bends. Not one. In fact, I've never in my life even seen it on any muscle car era Mopar I've ever been under.
 
The 9.25” rear ends have a 3.5” axle tubes that neck down to 3” at the backing plates.

So 9.25” Dakota u-bolts won’t work for an 8 3/4.
 
Well all Aussie mopars had "proper" u bolts
have a set sitting in "rustbuster" as we speak

maybe it was just factories in other lands that did it, or it was a heavy duty or harsh environment option?

read a write up years ago by RE in Mopar Action that covered off the benefits
presumed from that commonplace on 60s-80s mopars

Flat section with a vague waffle pattern on the area around the tube, and a warning in the factory manual about how to torque them and not doing them up too tight.

Dave
 
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Well all Aussie mopars had "proper" u bolts
have a set sitting in "rustbuster" as we speak

maybe it was just factories in other lands that did it or it was a heavy duty or harsh environment option??

Flat section with a vague waffle pattern on the area around the tube, and a warning in the factory manual about how to torque them and not doing them up too tight.

Dave
I've never understood what the big stink is about the flat u bolts anyway. It's not like they can hold any better than the round ones. Since the spring perches are WELDED to the axle tubes, the rear end cannot rotate regardless of WHICH u bolts are used. It's much ado about nothing.
 
pressure applied to the tube under the U bolt U = Force/Area

spread the force over a wider area = less pressure

i.e a perfectly round U clamp tends towards an infinitely small contact patch on the axle tube massive pressure over a small area causing damage to the tube

fat flat U bolt spreads the force over a wider area for the same torque on the nut

contact patch has an impact on friction between the two clamped items
bigger patch results in more friction up to a point.

not really about Tubes rotating at all. if it gets to that point all is lost.

U bolts need to provide enough friction between perches and the saddle on the spring so that the rivet or bolt that holds the spring together is not put into shear stress by the action of the perch-hole against its head when car is under acceleration.

i presume the torque specified for the mopar set up and a round U bolt resulted in kinked axle tubes and it didn't for the flattened u bolts

they won't have F++ked about doing an extra process that costs money when making the U bolt if it wasn't considered necessary for the intended use

but i do note that mostly nobody else did this....

Chrysler obviously had their "Extra care in engineering" reasons to spend that cash.

or maybe they just had a really **** bending machine :)

Dave
 
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If flat U-Bolts are your Bag.. Richard Ehrenberg sells em on ebay.. I have used round ones over 30 years without issue..
 
pressure applied to the tube under the U bolt U = Force/Area

spread the force over a wider area = less pressure

i.e a perfectly round U clamp tends towards an infinitely small contact patch on the axle tube massive pressure over a small area causing damage to the tube

fat flat U bolt spreads the force over a wider area for the same torque on the nut

contact patch has an impact on friction between the two clamped items
bigger patch results in more friction up to a point.

not really about Tubes rotating at all. if it gets to that point all is lost.

U bolts need to provide enough friction between perches and the saddle on the spring so that the rivet or bolt that holds the spring together is not put into shear stress by the action of the perch-hole against its head when car is under acceleration.

i presume the torque specified for the mopar set up and a round U bolt resulted in kinked axle tubes and it didn't for the flattened u bolts

they won't have F++ked about doing an extra process that costs money when making the U bolt if it wasn't considered necessary for the intended use

but i do note that mostly nobody else did this....

Chrysler obviously had their "Extra care in engineering" reasons to spend that cash.

or maybe they just had a really **** bending machine :)

Dave
Oh for God's sake, Dave. Find another argument. As long as you torque the u bolts correctly, you have zero issues. Now if you're stupid on the other hand.........
 
If flat U-Bolts are your Bag.. Richard Ehrenberg sells em on ebay.. I have used round ones over 30 years without issue..
Chrysler has used round ones longer than that. lol I swear, people find the stupidest things to worry about. LOL
 
I believe I saw this on Slant six.org a while back. Has anyone used the Dakota rear axle U bolts on an 8 3/4 rear end? They supposedly have the flat spots at the top of the u bolt
for proper alignment of the axle.

I have Dakota Ubolts on my 8.25 diff in my Dart.
They have the flat area.

The diff I have is an original 73-74 Mopar 8.25 with Jeep Grand Cherokee gears and sure grip in it with the Cherokee disc brakes.
The Mopar 8.25 and the Dakota 8.25 both have 3 inch tubes, as does a 8.75.
 
my 62 had flat ones (not muscle car era) for me it's not about clamping/holding but digging into the axle tube, i have taken apart a few with the tube a bit crushed (probably over tightened) and figured the flat would be a little better bout that
 
AMK has the correct u bolts in 2 different lengths. Most of the Mopars that I ever worked on had the flattened gripper u bolts. Hell, I have a couple 38 Plymouths and they used that flat u bolts way back in 1938-earlier even I think. I've seen the housing tubes pinched by round u bolts.
 
I have Dakota Ubolts on my 8.25 diff in my Dart.
They have the flat area.

The diff I have is an original 73-74 Mopar 8.25 with Jeep Grand Cherokee gears and sure grip in it with the Cherokee disc brakes.
The Mopar 8.25 and the Dakota 8.25 both have 3 inch tubes, as does a 8.75.

But the Dakota 9.25” has 3.5” tubes. I know this, because my ‘02 Dakota has a 9.25” rear axle with 3.5” tubes. Look at the tube diameter at the perches, and look at the tube diameter at the backing plate.

IMG_7431.jpeg


So if you buy Dakota U-bolts, you’d better make sure you’re getting them for a Dakota with an 8.25” rear and not a 9.25” rear.

And I’m with @RustyRatRod, if you don’t over torque the U-bolts you don’t need to worry about if the bolts are flat or round. The dimpled tubes come from guys over tightening the U-bolt nuts.
 
But the Dakota 9.25” has 3.5” tubes. I know this, because my ‘02 Dakota has a 9.25” rear axle with 3.5” tubes. Look at the tube diameter at the perches, and look at the tube diameter at the backing plate.

View attachment 1716274073

So if you buy Dakota U-bolts, you’d better make sure you’re getting them for a Dakota with an 8.25” rear and not a 9.25” rear.

And I’m with @RustyRatRod, if you don’t over torque the U-bolts you don’t need to worry about if the bolts are flat or round. The dimpled tubes come from guys over tightening the U-bolt nuts.
Yep, I know all this.
I was pointing out the original OP question regarding the 8.25 vs 8.75.
 
Yep, I know all this.
I was pointing out the original OP question regarding the 8.25 vs 8.75.

That’s great, but you can buy “Dakota u-bolts” that won’t fit an 8.25 or an 8 3/4.

It would be nice if someone listed the year range and models of Dakota’s that came with 8.25’s/3” u-bolts, since there are plenty of Dakota’s that came with 2.5” and 3.5” U-bolts too.
 
Oh for God's sake, Dave. Find another argument. As long as you torque the u bolts correctly, you have zero issues. Now if you're stupid on the other hand.........
"BUT I DO NOTE NOBODY ELSE DOES THIS" yeah.... that's what i said :) every other car and truck maker with leaf springs has no problem.......
If i was being stupid i would have let you get away with saying chrysler always used round U bolts, in my experience, which i guess will be less than yours, they most certainly didn't. I've been around enough rusted out wrecks from the US Australia and SA here in the UK to know this. dug through the piles of mopar shite at the swap meets left over from all the cars your US servicemen didn't take home.... been 1000s of you here since the 1940s and you all bring your cars, cant afford the fuel, or don't like driving on the wrong side of the road, park em till they rust and leave them behind.... I have learned that if its rusty with knackered threads and a ridiculous price tag proclaiming originality, it will be the flat waffly type

i might ramble on a bit but there is usually a reason based in truth or something that i genuinely believe based on experience :) my experience will be different from yours....

Dave
 
"BUT I DO NOTE NOBODY ELSE DOES THIS" yeah.... that's what i said :) every other car and truck maker with leaf springs has no problem.......
If i was being stupid i would have let you get away with saying chrysler always used round U bolts, in my experience, which i guess will be less than yours, they most certainly didn't. I've been around enough rusted out wrecks from the US Australia and SA here in the UK to know this. dug through the piles of mopar shite at the swap meets left over from all the cars your US servicemen didn't take home.... been 1000s of you here since the 1940s and you all bring your cars, cant afford the fuel, or don't like driving on the wrong side of the road, park em till they rust and leave them behind.... I have learned that if its rusty with knackered threads and a ridiculous price tag proclaiming originality, it will be the flat waffly type

i might ramble on a bit but there is usually a reason based in truth or something that i genuinely believe based on experience :) my experience will be different from yours....

Dave
I wasn't sayin YOU were bein stupid. I was makin a general statement.
 
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