What size rear end is this? is it strong?

[73_RoadRunner]

my uncle has a 75 dodge dart sport with a 360 904 trans and the rear end has the cover on the rear of the axle its not a dana or 8 3/4 i'm guessing its stock its probably 10 or 12 bolt is it strong? what siz is it? cause i plan on buying this car soon and building the 360 to have a lot of horse power 500hp or more

[kudah440]

sounds like it should be an 8 1/4.
if so Ive had one under my 440/727 a-body barracuda for about 5 years trouble free. unless you drive like a jackath, or throw on some slicks you should be fine. in the future you should plan for an 8 3/4, but im sure you already knew that.

[dave571]

They're not bad.

The car is light enough, that it will stand up to it, as said, without slicks ect.

[ehostler]

If you go into Tech Archives -> Differential/Rear Ends -> MOPAR rear axle spotter's guide, you will find an illustration that will help you in identifying the rear.

[dwc43]

Originally posted by 73_RoadRunner
my uncle has a 75 dodge dart sport with a 360 904 trans and the rear end has the cover on the rear of the axle its not a dana or 8 3/4 i'm guessing its stock its probably 10 or 12 bolt is it strong? what siz is it? cause i plan on buying this car soon and building the 360 to have a lot of horse power 500hp or more

If it's a stock 360 '75 year it will be an 8 1/4 rear. They are plenty strong and will also hold up to slicks nicely. The 8 1/4 was a replacement for the 8 3/4. THe 1/4 was cheaper to produce and just as strong since it went into all the hi po cars from '74 on out. THe 1/4 solved the housing flex problems that the 3/4 had that would cause caps to break and axle splines to strip. Most people dont like them 'cause they are a c clip rear, but I have not seen any problems from this. MAtter of fact we've used them in many race cars with no ill effects. And Moser makes a c clip eliminator kit for these rears. They also make an axle brace for the 3/4 to solve it's flex problem. The back brace for the 3/4 is not new. They've been around since the 60's and used widely in the NAscar racers back then. Glad to see some one still makes them. They make many ratios for your rear too in case you need a gear change in the future. Consider putting a tranny cooler on that 904 though. They are a weak link and a A727 would be much better.

[dave571]

Originally posted by dwc43


If it's a stock 360 '75 year it will be an 8 1/4 rear. They are plenty strong and will also hold up to slicks nicely. The 8 1/4 was a replacement for the 8 3/4. THe 1/4 was cheaper to produce and just as strong since it went into all the hi po cars from '74 on out. THe 1/4 solved the housing flex problems that the 3/4 had that would cause caps to break and axle splines to strip.

dwc, when you say the 8 1/4 solved the flex issues of the 8 3/4 it sounds like you think it is a better differential. Is this what you're saying? That the 8 1/4 is better than the 8 3/4??

Not trying to start one of these , Im just trying to clarify you stance on the subject.

I have broken these differentials, and find the suggestion that an 8 1/4 is as good as an 8 3/4 rather difficult to comprehend, but if you believe it, power to ya.

Is an 8 1/4 good enough for a street small block in an A body. Absolutely

[dwc43]

They are equal not one better than the other. The 1/4 did replace the 3/4 and those were Mopars reasons for doing so mentioned in the other post. There is only a 1/2 in. difference in ring gear size. The axles are the same size basicly. I have broke a cross shaft in one but that's it. Ive never broken anything else in a 1/4. I have never broken a 3/4. I did break a ring gear in a 4x4 9 1/4 one time though. On the street at that. Not into the mud pit stuff.
But yes the two are pretty equal. I've raced with both on dirt and asphault with good results. I do prefere the 3/4 for quick gear changes though.

[RATED X]

i called a ring and pinion guy today about gears for a 8.25 rear and he said to me that on a 4.10 ratio you need to grind one of the teeth off the ring gear for clearence.whats up with thatand do you know if the back plates are interchangeable from 8.75 to 8.25 thanks

[dwc43]

That's a bunch of bull and you need a new ring and pinion guy. Go to Randy's Ring and Pinion and he will set you up with what you need. His site is www.ringpinion.com Backing plates wonmt swap.

[Manning]

Yes, backing plates are interchangeable and thus the brakes too. I believe the ends are also the same as the dana 60.

Originally posted by RATED X
and do you know if the back plates are interchangeable from 8.75 to 8.25 thanks

[dave571]

Originally posted by RATED X
i called a ring and pinion guy today about gears for a 8.25 rear and he said to me that on a 4.10 ratio you need to grind one of the teeth off the ring gear for clearence.whats up with thatand do you know if the back plates are interchangeable from 8.75 to 8.25 thanks

There are situations where the ring gear is too big for the case. It' won't go through the hole/pan removed area.
I don't think this is the case with a 410. but if it is, you grind a small portion off of the case, not the gear.

A small notch, in the pan surface, will allow the gear to enter the case. This is actually a fairly common mod on smaller brand X diffs

[RATED X]

it was randys ring and pinon . im going to call again and find out exactly what he was saying . he did recomend that i use 3.90 ratio cause it was simpler but he did say to grind something thanks

[dwc43]

It had to be the housing, then. You never grind on the gears themselves.

[b-1ken]

Bob, do you really want to put a 4.10 into that Satellite? I thought you were talking mid 3's.

[RATED X]

hey i wanted to call you .i asked what ratios they have and this guy tells me that 4.10 are bit of a problem i was really thinking about 3.90 that should be pretty good al around gears . by the way what they heck do you need to grind on that install

[b-1ken]

3.90 is too stiff for me! Something like 3.55 sounds better. The grinding they are talking about is to be able to fit the ring gear into the housing. The opening is too small for high numerical ratios (ring gear is thicker), so you have to notch the housing to get the ring gear in. Your guy wanted you to knock a little off one of the ring gear teeth instead. I don't think that it's any big deal.

[ehostler]

3.55 is a much better all around gear. The 3.90 is going to be reving at high RPMs on the highway.

[RATED X]

i might just leave it alone.the car drives real good .it might be a let down if we go to the track .but that wont be that often.by the way i put 35 shooters in that carb it still stumbles.i am going to put 38 in it see what happens. hey ill be back on the 15 lets get to work on 37. give me shop time over there

[b-1ken]

Make sure that the accel pump linkage is in contact with the cam at idle. The check valve(s) might also be bad. Did you rebuild the carb? I think it's smart not to go with 3.90's. You have too many open highways out there.
Here's a reminder what you have to look foward to.

[RATED X]

i having nightmares allready dont worry she will be beautiful i bought tube type shooters40 thats all they had at checkers it was much better but it didnt sound clean ill try 38 its a brand new carb 650 dpi tried some cams on the acc pump trying to workthat ill keep you posted

[b-1ken]

I know, you'll get right on it "AFTER CHRISTMAS"