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#1
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8 1/4 rear end traction questons
I know I should pony up and get a 8 3/4 but for the sake of argument and saving a few hundred bucks I'm curious if anyone has had much experience switching an open carrier 8 1/4 to a posi. Its a 73 Dart Sport that was originaly a slant six with 904 and is now a 360/727. I'm not exactly sure of the ratio but at 75 mph I'm turning 2,800rpm on 245/60 15" tires. So I'm guessing 3:25's. I've found the Auburn and the Mopar units pretty reasonable and wondered if anyone had any input of which is better. I've played with Ford 9" and Chevy 10 bolts but this is my first adventure into the world of Mopar rear ends.
Right now at anything under 20mph if I stab the gas it annihilates the right side tire. |
#2
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Unless you're running big power the 8-1/4 will do just fine. I have a 1976 Aspen that I bracket race and it lays down 1.51 60ft times and runs 10.75 consistantly with an 8-1/4 rearend. The reaerend has over 400 passes on it and is still in good shape. I have a sure grip with 4.10 richmond gears. In my opinion the Sure Grip in the 8-1/4 is stronger than the 8-3/4 but some people don't. I wouldn't worry about the strength if you're not going any faster than I am. Add a pinion snubber and some drag radials and you'll have alot of traction. I just switched to CalTracs and their monoleaf springs and Rancho 9000 shocks and I love it. I run a 9" M/T slick so traction is excellent. Good Luck!!!
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#3
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I have an Auburn in my 8 1/4 (360/904 Mirada) Had the rear freshened and a new unit installed in 02 when I swapped out the 7 1/4. Absolutely no issues since, but I'm not racing it either.
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#4
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I eventually want to put an 8-1/4 rear in my Duster too. Do all 8-1/4's have large bolt patterns? Can the gears be easily swapped out, kinda like an 8-3/4 rear?
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#5
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MOPEkid, I have an extra 8-1/4 for sale right now if you're interested. It's out of a 1976 Dodge Aspen. It's got a Sure Grip, pinion snubber, 4.10 Richmond Gears, and Moser axles. I'll sell it very reasonable. If you're interested, call me at 218-689-2586 Ryan
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#6
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Correct me if I'm wrong, but weren't later (mid-70's and later 8 1/4, 9 1/4 ) Mopar Suregrips a cone-type lsd - aka Auburn? as opposed to clutch-type as in PosiTraction used in the 8 3/4 and Dana rears?
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#7
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dartster73, the rears set up easy. You should not have a problem in doiong one yourself or having it done. Mopar, auburn, etc... make posis for it. Gears can be had in all sorts of ratios.
Quote:
2. No |
#8
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I guess more specifically, do 8-1/4" rears exist for '70 A-bodies with large bolt patterns? And how common are they if they do exist?
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#9
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Yes, the larger bolt patterns are found in the later years. I forget what year they started in though.
Fairly common. I picked mine up for $200 with a 3.21 suregrip inside. Add 5.9 for a rattle can of black paint, presto. |
#10
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A body large bolt pattern began 73 model year
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#11
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So I wouldn't have any problems putting one in my '70 Duster? $200 is pretty good, I thought they were going to be $400+.
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#12
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Thanks Dart14.
It was $200 without backing plates for the brakes. This is something I didn't mind since I had and intended to use (And did) a set of 11 inch drums. |
#13
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You can get a direct bolt in. And I can pick one up here locally for $100 ready to install. Just did one last spring in a Volare'. Took it from a Wagon at the junkyard for $100. : up:
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#14
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That's not just opinion there. You'll find it in the Mopar Chassis books that the 1/4 was desinged as a replacment for the 3/4. It's actually stronger and cheaper to produce. It does not have the flex that the open banjo housing of the 3/4 has. Therefore it does not easily brake axles and bearing caps and such.
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#15
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I've heard that before.
Can you scan in the page that says the 8 1/4 is stronger than the 8 3/4? Then you could post it here for us to see. I for one would like to see that info, and have never read anything like that before. Thanks |
#16
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What do the 8 1/4" you guys are talking about relate to the 8.25" rears in trucks like the Dakota and Cherokee?
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#17
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What do you mean Joe?
There basicly the same rear. Room was made for the anti-lock ring. Axle spline count changed. |
#18
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I've been told (think it was a Mopar Action item) the Dak axle is a beefed-up 8 1/4 with slightly larger (8 3/8) ring and better axles. dwc, you sure you're not referring to the 9 1/4, which I had heard was the stronger replacement for the 3/4.
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#19
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DW has been screaming what he wrote for years and is the only one doing so.
Both rears, 8-1/4 or 9-1/4 are C clip rears that came about the same time. The C clip seems to be a problem for many people. I have one of each with over 300,000 miles on it (Each) and it see everyday driving just fine. I'm not a light footed driver by any means. |
#20
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C-clip eliminating mods have been a good seller to GM folks, but I've never heard of a Chrysler C-clip design giving problems. More to the point, I've never seen a "C-clip eliminator" advertised for a Mopar.. I have re and re'd axles on my 8 1/4 as well as on our 89 S-15 Jimmy and I didn't see a lot of difference in the design principles, so I assume it's engineering excellence in our favor, again! BTW, I paid around $400 for an overhaul plus a new Auburn unit several years ago, so rumble's deal is definitely a DEAL!!
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#21
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Quote:
I've read different things about this axle, some people thing they're as weak as the Dana 35 hwile others claim they're as strong as the Dana 44 in the Cherokee applications, especally if you get the later 29 spline axle (IIRC mine and Swinger's should have that ) What limited slip units are there for this axle? Most of what I see for my application is either for D35 or D44 |
#22
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When have you ever seen dingleberry post a scan or diddly squat to back up anything Dave?....Hope you are doing well Dave....old age has taken the toll. Dart is going on the block in the spring......heres a fun shot of the "moonbat".... some things never change...
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#23
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MoPar sells a suregrip unit for the 8-1/4 axle.
So does the other companys out there. Ummmm, errrrr, drawing a blank, thiiiiiiiiiiiiiink..... crap! fire alarm just went off..... smake from the dome set it off. All's good. Auburn! HA! ummmm , brain fart....... |
#24
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8 1/4 Diffs
Just a quick heads up from someone who's been there...
The Aspen / Volare rear ends are not a direct bolt in on a Dart. The shock pltes are different as is the shackle attachment. I used the Springs and shackles off my 7 1/4 and cut and welded the shock plates in the right position. |
#25
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For sure.
Good to see you on the board man. Missed you at the olde time race the last couple years. In all seriousness, if an article that states the 8 1/4 is stronger than the 8 3/4 really exists, I would love to see it. I've seen the attached pic before, and have no problem with Dwc peronally. I'm not anti 8 1/4. I've abused a few and broken one. I would not hesitate to use one, if I had a car with one in it, BUT I'd just like to see this claim backed up if at all possible. |
#26
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The problem you might have in installing a sure grip in your differential is adjusting the carrier bearing preload and backlash. You need a special tool to go in thru the axle tube to turn the spanner. I made one for myself. Also if you are going to race it, and go quicker than 11.00 et at a NHRA track, you will need aftermarket axles and a c-clip eliminator kit.
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#27
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I have a 8 1/4 in my dakota. 220,000 miles on it and I beat the hell out of the truck. I did put a trac lock in it at 170,000 It could lock harder but it works. Randy's ring and pinion sells the tool to adjust the spanners I think it was $35 if I remember correctly.
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#28
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Still waiting.......
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#29
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Quote:
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