8 1/4 Rebuild

[Jasonb61]

Hello,

I am wanting to build up a rear end that can handle some pretty high HP... I need some reassurance on building the 8.25 (8 1/4) rear that comes on the early dakotas... If built properly with a good unit and axles, how much abuse could they handle?

I have two 1987 Dakota 8.25 rear ends sitting out in the pasture (haha, redneck as it gets when you have two parts trucks in your pasture!)... Both are still under the bed so they havnt been exposed too terribly...

I basicly need some tips on rebuilding a used rear but building it to hold up to some power and abuse. I plan on upgrading to Superior Axles (found on summit I believe) and not sure about the guts of it yet... But like I said, I just need reassurance that building a 8 1/4 rearend for a 408 Project is a good idea... I dont want to build it all up, go to the strip and make an ass of myself haha...

Thanks,
-Jason

[HemiDak]

Besides chromoloy axle shafts, I'd highly suggest a Detroit Locker or a spool. You'd definitely want an extra-capacity diff cover to keep the temps down as well.

Also, don't forget the c-clip eliminator.

I'm sure it could handle all the abuse you could throw at it then. Mine's held up well offroad with a Detroit and 4.56 gears.

[Jasonb61]

Hmm Where could I pick up the Chromoly Axle Shafts? That's one thing I didnt think about...

[HemiDak]

I've looked into it before and I believe Yukon makes some. I'm not exactly sure, but would just have to make some calls around. Maybe Summit would be able to look them up.

[realdeal7369]

could always get a rearend manufacturer to custom make you a set of axles too. forget the names of some of them though, but maybe randys ring and pinion, could do something. moser engineering.? just a few off the top of my head. once done right, i dont think you'll pop it. just get a very good diff, as suggested, good axles, and a higher alloy driveshaft yoke too. a good driveshaft from dennys is a good idea too. wouldnt want to see you snap one like a twig. how much power you plan on having?

btw, ive seen these 8.25, running in the 10's with no problems. :biggthump

[rt99three60]

get some moser axles , id just find a good rear end shop and tell them u want it to handle this much HP and have them build it up for u

[HemiDak]

Moser does make custom axle shafts and would be a good start for getting prices. Let me know if you find anything on it as I might be interested in what you find out as well.

[Jasonb61]

I'm not saying I will have this much HP, but I'd like it to hold up well to 500 HP... It'd keep my mind at rest because the 408 is almost done and MAYBE if I get ballsy enough, I'll throw some juice on that or a blower... MAYBE... I just want to build the rear up and be done with it! Could it hold that 500?

[ScatDak]

I used to have a 8 1/4 in my 73 Charger with a 340 I never had a single problem with it. I think the 8.25 is underrated it can handle more abuse than what is to be believed

[Jasonb61]

I thought the chargers have the 8 3/4?? Ha but I am usually wrong lol. So do you guys think it could handle that abuse? Any stories of someone actualy destroying one of the 8 1/4 and what its breaking point was? I'm really in a bind here and I need to make a decision soon. Please help!

Thanks,
-Jason

[Jasonb61]

Ok, bringing a thread back from the dead... :sorry: Do you guys still think the 8 1/4 will stand up to a blown 408? Or should I save myself the worry and go with a bigger rear?

[DaKoTa-BoY]

i dont know but i do know that one guy had a 400/727 combo in his dak w/ the 8.25 rear and it withstood the 3k launches at the track all day long, never had any problems....so i'd guess that it will hold up

[R&SR/T]

C clip Eliminators would be a good idea if you go with an 8.25 too...I had an 8 1/4 in my Scamp, but swapped it over to an 8 3/4 when I dropped the 340 in. I spent the same money getting it (with the gears I wanted) as I could have beefed up the 8 1/4 with a power trax, axles and changed the gear ratios. I would say it's really on what kind of a deal you can find on an 8 3/4.

[Jasonb61]

If I could retain my ABS with an 8 3/4 then I wouldnt question the swap.... Is there anyway I can keep it maybe???

[realdeal7369]

Hello,

I am wanting to build up a rear end that can handle some pretty high HP... I need some reassurance on building the 8.25 (8 1/4) rear that comes on the early dakotas... If built properly with a good unit and axles, how much abuse could they handle?

I have two 1987 Dakota 8.25 rear ends sitting out in the pasture (haha, redneck as it gets when you have two parts trucks in your pasture!)... Both are still under the bed so they havnt been exposed too terribly...

I basicly need some tips on rebuilding a used rear but building it to hold up to some power and abuse. I plan on upgrading to Superior Axles (found on summit I believe) and not sure about the guts of it yet... But like I said, I just need reassurance that building a 8 1/4 rearend for a 408 Project is a good idea... I dont want to build it all up, go to the strip and make an ass of myself haha...

Thanks,
-Jason

get a good differential, good gears, and get one of those lpw aluminum rearend caps too. ive seen 8.25 rears taking abuse of sub 11 second high 10's punishment.

how much torque and hp you looking to make?

[R&SR/T]

The 8.25 backing plates are a direct bolt on to the 8.75. I would move all brake hardware including lines over. Since they are a direct swap, I wouldn't see any reason why you couldn't retain your ABS's.

[realdeal7369]

Ok, bringing a thread back from the dead... :sorry: Do you guys still think the 8 1/4 will stand up to a blown 408? Or should I save myself the worry and go with a bigger rear?

just build up the 8.25. i think youll be ok. if need be, look into slightly bigger spline axles. i think stock they are pretty beefy though (29 spline), look at moser or some other company. get like a 31-32 spline or something close to that. but i think youll be ok, with an upgrade with the stocker.

[realdeal7369]

The 8.25 backing plates are a direct bolt on to the 8.75. I would move all brake hardware including lines over. Since they are a direct swap, I wouldn't see any reason why you couldn't retain your ABS's.

abs dont run off the brakes at all. there is a little ring gear in there that it reads off of. the 8.75 rear dont have this setup.

[01SilverDak01]

The 8.25 Diff can be built up to handle all the Power you want, and do it without breaking you financially....

Both My Dak's have 8.25 Diff's, and I beat the Snot out of them!

[Jasonb61]

abs don't run off the brakes at all. there is a little ring gear in there that it reads off of. the 8.75 rear don't have this setup.

I wonder if I could have the 8.75 machined or something to be able to add that sensor? If not, it looks like I'll be running my 8.25.... as far as horsepower and torque - I'm really not sure how much my motor will make... I'd like the rear to be able to handle maybe around 500+ HP... That doesn't mean I'll be making that but you never know lol... it also needs to be able to take hard launches, frequent burnouts, and romping the hell out of it :jester:

[realdeal7369]

I wonder if I could have the 8.75 machined or something to be able to add that sensor? If not, it looks like I'll be running my 8.25.... as far as horsepower and torque - I'm really not sure how much my motor will make... I'd like the rear to be able to handle maybe around 500+ HP... That doesn't mean I'll be making that but you never know lol... it also needs to be able to take hard launches, frequent burnouts, and romping the hell out of it :jester:

you should be fine with the 8.25. getting the 8.75 rear mashined is alot. finding a spot to mount that sensor in there, and getting the depth right and all that. screw that. if your that worried about it, get an r/t rear (9.25). make masurements and all that, then shorten it if you need to. cost will probably be alot less than that 8.75. youll also have to machine the gears on that 8.75 in order for that toother rind that the sensor reads off of to fit.

too much to bother with if your on a strict budget, and wanna get your shit running.

get an auburn diff, good 3.92's or 4.10's, get that aluminum pan for it, and maybe investigate axels. like i sid, and ive also read this in hot rod too. (as they tested the limits on certain rears too). you can run high 10's with that little rear, with no worries.

hard launches with slicks? is this with a stick shift? lots of factors are involved too to consider. if you have a stick shift, id say get a dana rear 9.25, or call up currie enterprises for a rear speacially built for your application. prolly a dana 60, or a ford 9" built to fit.

[Jasonb61]

no ford parts boooo :jester: It's an automatic and I really dont know If I'll be in the 10's or not.. I really dont know what to expect from this motor haha... Oh, do you by chacne still have the ssbc kit?

[Jasonb61]

Finally starting this now... What do you guys think about Lpw Covers?

http://www.lpwracing.com/p_capcovers.asp

Maybe something else? Seems like a good product to me.

[Jasonb61]

ok, i need your reassurement one more time that if I build this rearend the right way, it will hold up to 10sec runs or more. What is the weak point in this rear?

[Dakdood]

I managed to shear all of the ring gear bolts off... that was the only problem I ever had with my 8.25...

[Fluffy]

I'm sure it could handle all the abuse you could throw at it then. Mine's held up well offroad with a Detroit and 4.56 gears.



With an 8 1/4? Really? :waiting: I was told these break easily with over 3.90.... I've got one in my truck now, and I was planning to upgrade to 9 1/4.

If I can throw sure-grip and 4.56s in the 8 1/4, I'd rather do that.

[donram360]

I'm about to assemble mine for an old Volare. I'll let u know if it breaks.
New Sure Grip, a set of NOS 3.55 R&P, and a randys Master install kit.