I had two more links bookmarked with the absolute bestest info on these, but like a dumb***, i didn't save it to the pc, and the sites are old and gone. These are what i've got left- plenty of good info still. http://members.tripod.com/~Mojo_Page/chry875.htm http://www.usaimports.co.uk/Mopar_Tech_Pages/mopar_rear_ends.htm http://www.quickperformance.com/Technical Info/sus_measure.htm
We ran 8 3/4 both the 742 and 489 in our blown gas dragsters. Went 195 back in the late 60's . A buddy ran top fuel went 240 with his. never broke one. We did wear a few gears out. We even ran the 742 with positraction before spooles were cheap. My son has a 742 in his 351 Cleveland dragster 190 mph with trans brake. No problems. Pretty light car however but runs nitro. I have a 9 inch in my Willys and already have damage to the splines after 1000 miles on the street. Pattern looks great however.
Yep, B, E, and C-body 8.75's are easy to find though. Leave those A-body ones for us muscle car resto guys (hope I didn't say "muscle car" too loud).
We're not going here again are we? There was a whole thread on here arguing about this - the A body 8 3/4's were all 4 inch bolt pattern. in '73 Mopar started using the 8 1/4 integral carrier rear with 4.5" bolt pattern in Some A bodies, as well as a 7 1/4 with 4.5" bolt pattern if the car had front disc brakes. The Moser axles to convert to big brakes and 4.5 bolt pattern or resplining C Body axles are the way to get a big bolt A-Body 8 3/4, or narrow a C-body or B-Body (or truck or van) unit.
Happy to help.Im still learning on Mopar stuff ,but i like what i have learned so far (both researching and hands on).The Chevy and Blue Oval Diehards dont know what they are missing out on .Old Mopars are freaking awesome and very durable dragcars...
Here is mine with 4.57 gears and surelock 4 1/2 WP shortened to 40"s back plate to back plate. These are great rear ends and like all have stated they are strong.
I have an 8 3/4 in my 1931 Ford, 1940 Dodge Coupe, and 1970 Dodge Challenger.... everything but my 1957 Chevy truck...
I used a shortened 69-70 C body 8 3/4 with 489 center, 323 gears, comes with big finned drum brakes, 4 1/2 bolt circle, & set it up with the green wheel bearing kit too.....
You can all talk about how much horsepower you made or how fast you went, but the fact is (and has been mentioned previously), the housing itself is ****. Its thin, and it ****s. If your car went fast with it and it stayed together, your car is light or leaves easy. My 64 Olds had an 8 3/4 (489 case, 4.57 gear, spool, etc) up until January of this year. 3000lbs, 14x32 M&H racemasters, ladder bars, and 1.44 60-foot times with a transbrake turned it into a horseshoe-shaped metallic cluster****. Bent the housing up and forward, twised the RH side tube around 5 degrees. This was WITH a backbrace for those that think they matter. It never cracked a bearing cap, but I was probably on the edge of doing so. It now has a 9" with HRW case and 35 spline Moser axles. Trying to re-use the 8.75 and saving money actually cost me fortune fixing it again later by removing it entirely. 9" or Dana, unless your car is really light or doesnt make enough power to hurt anything. I gambled and lost.
The facts are: If your drag racing an 8 3/4, you HAVE to have a pinoin snubber or you WILL bend the housing at some point. These axles are designed to limit the axle rotation by limiting the center section movement. Most guys that bend the housings are trying to limit axle rotation at the springs. Those housings simply won't take it very long. A back brace may help a little, but that is not where the load is placed, the load is at each side of the center section and is a nose up twisting action. A back brace is simply on the wrong side of the housing to be most effective. The most effective way of solving the housing bending issue is to make brackets to attach to the nose of the center section and have a solid part of the ch***is for the nose bracket to contact to limit the centers upward rotation. Used to be able to buy an adjustable pinoin snubber from Mopar for this purpose, probably still can. I suspect the reasons most rail cars don't bend the housing is because the suspension (or lack of) is attached at the edges of the center. Yale fork trucks used to use 8 3/4 axles under their fork trucks up to 15.000 lbs, but the axles were attached to the trucks using the center section bolts. Gene
I owned a '72 with the larger bolt pattern, that I bought from the original owner, and he never touched the rear axle, ever! So, at least ONE was equipped this way. No, I'm not going down the same road again, just stating fact. YOu are right about the C-body 8-3/4 axles being the best bet for narrowing, as they were by far, the most plentiful.
Okay, obviously it has limits, but I have seen many, many 10 second cars with an 8 3/4 that live a long time. Adding a transbrake to the scenario means all bets are off and you should step up to a Dana or be prepared to spend big bucks on a 9" Ford with very few or no Ford parts in it. In the Mopar realm, most 10 second cars are running Super Stock springs and the above mentioned pinion snubber. Ladder bars stress the housing in a very different way. What kind of times does your Olds run and what RPM are you leaving on the brake?
Why did I think that everyone already knew this? This was just about the very first modification we ever made to all of those 60's-70's muscle cars. I am baffled as to why some folks fail to understand basic physics, or for that matter, why they don't bother to read the Factory race literature. I still get a real good laugh when I see a Mopar with ******* bars... .
Hey all, I just found this web page while searching for something else: http://www.rosevillemoparts.com/reference_enginetrans9.php .
Not to change the station too much ,but the usual reason people think that ******* bars dont work ,is because they dont set them up correctly.Lots of people set them with the wrong gap on the snubbers ,or even worse position the snubbers behind the spring eyes (where the spring is a single and its weakest point),instead of directly under them .I know guys that are "rebels" and getting 1.30 60 foot times on old fashioned ******* bars with Mopars ...
Its a mid to high 10 second car. I leave the line around 3500, stall is 4600 (its from Lenny @ Ultimate Converter). Trap speed is 125+. I was saving up to put a much hotter engine in it and THEN replace the 8.75 later, but the reality was that the rear went noodley(?) first and there went the engine fund...
so i went and checked my numbers today and the one im using in my 55 is a 742 out of a 383 fury width came out to be an inch wider but doesnt hurt me much with the radiused fenders.
I know they can work when set up properly, but they always look like they should be on a '68 Nova or Camaro, painted bright yellow (or rusty chrome) beside some n50 Kelsey Super Chargers on peeling chrome Cragar rims and with air shocks pumped up to 120 lbs. The 10 bolt should be painted red or white and there should be some lights mounted underneath to show off the rusty chrome cover and rusty gas tank. Probably a pair of Thrush gl*** packs under there somewhere too.
All I know is I have wrecked every thing but my 8 3/4 in my drag car ,including last year a drive shaft I like them and ford 9,s simple, if ya watch what your doin way cheaper than a dane 60
I've been watching your progress. The faster you go, the harder you leave, the more likely your going to bend the 8 3/4 housing if you don't have a snubber on there. Its just a matter of time. Never said the ******* bars don't work to put traction to the ground, but I promise the housing will bend at some point with limiting the center section rotation. Back in the day when we were dirt track racing, we used to paint lines the length of the axle shafts. When we twisted the shafts 1/4 turn, we replace the axle shafts. Dirt track racing puts a lot of stress on the axle shafts. Gene
Just a little added info that wasn't mentioned. The biggest reason for using a "C" body axle to narrow is that you don't have to buy new axles. There's enough meat at the spline end that they can be shortened and resplined to fit the new narrow length. Other than that, one can narrow almost any Mopar 8.75 rear. The rear diffs have two different "Sure-grip" units that you might find. One was a (Eaton?)cone-type, that is generally not rebuildable. The cones can be cut down a bit to make them work, but that hurts the internal preload built into the unit. The other one is rebuildable, (Dana?), and is typically the preffered unit to get. Either will swap into all three casting centers. Roger
...we did the same thing drag racing. Back when I was breaking parts the hot cars simply never used any 'bars', rather, the springs were carefully ***embled with what we thought would be required to control wrap (several ½ leaves) as well as launch (the rest of the pack). But we also still used a snubber and had to reinforce the floor area above it. We followed the Mopar Performance guidelines and it served us well. The old books still have valuable information. ajmopar well describes the 'usual' ******* equipped brand x cars from the old days.. .
My brother's car uses an 8.75 from a 72 chrysler imperial I found at our local u-pull-it. I pulled it our on a 100 degree sumer's day. It was a 3.23 posi but the wheel bolt pattern was 5 on 5"..same as big GM and big Ford in the 70s on their big cars..LTDs, Lincolns etc. We sent the imperial shafts to Moser to have them shortened. Moser wouldnt' shorten 'em because they said they were so thick at the point we needed splines that we'd loose all the hardening. They were kind enough to supply us with a pair of the smaller mopar axles to shorten and respline. Car has gone 10.32 and has since been fitted witha aftermarket shafts to comply with the rules but the little car never broke any axles or housing. BTW, this car runs a pinion snubber and always has. Launches off the trans brake for some wild action! 86" wheelbase makes for some serious fun...
I agree with you on the housing twisting at sum point ,although with 1.50 60's it may take a while.Your correct on the only thing keeping the axle housing from rotating up without a pinion snubber is the spring pads.I have seen early Olds/Poncho rearend housing twist as well as a 9inch Ford.I have also seen a 10 bolt GM roll the center on the axle tubes .Everything has its limit.On the other hand i know of Mopar guys that are running S/S springs and refuse to run a pinion snubber and getting 1.30 60's with 8.75 rears as well as Caltracs.I was mainly talking about the mechanicals of the 8.75 being stout ,(case, axles ,caps ,yoke ,etc).The sheetmetal housing is the weaklink for sure regardless of the make ...
The Jalopy Journal
