Recommended posi rear end?

-
KramerSwinger70

KramerSwinger70

70 Dart Swinger360
Joined
Sep 17, 2009
Messages
984
Reaction score
13
Location
Rohnert Park, CA
hope im in the right place in the forum. trying to compile a list of needs for my 70 Dart. i have a /6 right now but will eventually swap in a 340 or more likely 360 (cheaper....jus a 18yr old guy). so was wondering, what posi rear end would you guys recomend for me? ive heard maybe 8 1/4 suregrip? honestly ive no idea. keep in mind, the car is gonna be a daily driver, so street gears :toothy10: thanks!
 
How much power you plan on putting out? More importantly do you plan on running tires that will hook up? If not, then most likely a 8.25 sure grip will be just fine. If you plan on hooking up some power than 8.75 rear end should be the minimum you should use.....it all just depends on what your trying to do.

....oh and mopars don't have posi, they only have sure-grip, a posi is a chevy diff. Lol:toothy10:
 
...oh and mopars don't have posi, they only have sure-grip, a posi is a chevy diff. Lol:toothy10:[/quote]

my bad. buddy of mine who is a bit moretech-smart calls it posi...hes a chevy guy. thanks for clearn that up for me!

i expect to be running somewhere between 240-270 horse? not gonna be a major street killer, jus a good 13 sec car on the 1/4. so 8.25 suregrip is good for that?
 
any suggestion on the gearing? im still kinda learning the ins n outs of all this so ive no idea haha jus need numbers so i kno what to ask for
 
73charger said:
any suggestion on the gearing? im still kinda learning the ins n outs of all this so ive no idea haha jus need numbers so i kno what to ask for
Click to expand...

since you say you want to keep it on the street and say you might want to drive it on the highway occasionally then go with a 3.55, good all around gear that will give the best of both worlds.
 
u could always go 3.73 or better with a gear vendor!! i know those things are expensive but awsome!
 
stuoid question but gotta ask. i found an 8.25 suregrip differential on summit racing.com. would it be possible to swap out the differential on my original rear axel(for slant6) and jus put the sure grip on the same axel? ort do i need an all new axel and differential?
 
73charger said:
stuoid question but gotta ask. i found an 8.25 suregrip differential on summit racing.com. would it be possible to swap out the differential on my original rear axel(for slant6) and jus put the sure grip on the same axel? ort do i need an all new axel and differential?
Click to expand...

is your origional rear end a 7.25 rear? If it is then no you cant put a 8.25 diff in a 7.25.

If you don't know for sure what it is just count the number of bolts on the rear cover. If it has 9 bolts then it is a 7.25 and if it is oval shaped with 10 bolts then it is a 8.25.
 
ok i just wanna make sure im clear. i checked my rear end and its got 9 bolts on the differential. so if i buy a 8-1/4 differential i can hook it up to my current rear axel and be set? i mean, is the axel strong enough? it is, after all, for a slant six. also, with a new differential, will i need a new driveline to handle the new horses?
 
73charger said:
ok i just wanna make sure im clear. i checked my rear end and its got 9 bolts on the differential. so if i buy a 8-1/4 differential i can hook it up to my current rear axel and be set? i mean, is the axel strong enough? it is, after all, for a slant six. also, with a new differential, will i need a new driveline to handle the new horses?
Click to expand...

No, if your rear end has 9 bolts then it is a 7.25 and you can NOT put a 8.25 sure grip in it...it wont fit/work.
 
Everything that's between the rear tires will have to be replaced (except leaf springs and stuff). I believe the driveshaft length to be different as well.
 
damn my excited reading. didnt realize thanson sed can't. could of swore it was can! crap. how much should i expect a 8.25 rear axel to run me?
 
Hey Kramer,
Just keep an eye on craig's list and one will come up if your looking just like the 340/360 your looking for . I picked up a nice A body 8 1/4 off craig's for $125 . The guy was swapping out for an 8 3/4 his buddy had sitting around.
Keep an eye out for a whole car with motor/trans/rear end /radiator ect in good shape. Maybe a car that has a lot of rust or wrecked ? It would be a lot cheaper than buying ever thing separate.
That's what I did on my 69 319 K member disc brakes , power brakes, power steering , 22" radiator, drive shaft, rear end 7 1/4 large bolt pattern till I have the $$ to make my 81/4 a suregrip ? It would make a lot of sence to do it this way instead of peice meal unless you have unlimited funds or don't mind if your car won't be running for a while? Good luck with your project and email me if you have any questions .
passengers.jpg
 
you can find them fairly cheap yet, some people will practicley give you an 8.25. The most I would pay for one is 100,(unless it was already built with a decent set of gears and a suregrip)
 
Somehow I have managed 700 runs or so on my stock 7.25" (2.76 gears). Granted, I'm only pumping out 150 horses or so with my slightly modded six, but still ;) It's about time to get on with my 8.75 project that I keep putting on the backburner.
 
You should look for a 8 1\4 rear end they have the large bolt pattern wheel bolts, the better brakes that are readily available at any parts store and usually have 321 gears. Moparaction.com should have an article that outlines the procedure for making the 81\4 as strong as the 8 3\4. The only real advantage of the 8 3\4 is the drop out pumpkin. Stay away from the 355-1 and lower gears on a driver they are too much.
Mopar trucks have posi diffs and the diff oil for lockers from mopar says "posi" on the container with a mopar part number. Good luck and keep asking questions to get different opinions.
 
well accordin to a 1/4 mile calculator, if my car will weigh 3100 w/ myself in it and a 240 or 360, at 270hp itll run 13.8....its just an assumption. but wut i meant by that was it wnt be the fastest dart, but itll be fast enough to rub my chevy buddies noses in it :bootysha:
 
You must log in or register to reply here.
-

Back
Top