8-1/4" rear end questions?

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MoparFan

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I have read a couple of time that the 8-1/4" would be good for about 400hp... and I alway wonder what is the weak point of that rear-end?
Is it the axles? The gears? Both?

I'm just curious...that's what I have in my Dart now, and I am still very very very far away from the 400hp (72 318 2 bbl all stock, almost :sleepy1: ). Power should increase in the next years, don't know if I will it 400hp one day...I wish.

Thanks
 
I think based on its size, the weak link in a 8 1/4 is its axles they are smaller then any other rear end in its class. I will also use the 8 1/4 in my 71 Dart. Mine is a two door. I will be adding disc brakes soon. I can rebuild a 8 1/4 cheaper then you can rebuild a 8 3/4. They stopped using the 8 3/4 a long time ago. I think the 8 1/4 is still being used. Look under a Jeep Grand Cherokee the next time your driving down the road. I did notice that the 06 G.C. are using yet another rear, but I have yet to find out what it is.

Are you limited to the tire size you can put on your car? Just wondering
 
The G.C. gets a 9 1/4, the same as the Durango has.
 
I know that they have use the 8-1/4 for a long time, and I also remember that the number of spline has change in the late 80's, bu t I can't remeber wich year.
I will look for Dakota, Ram or Cherokee axle to try to find a better number then the 2.45 that I have.
But for that I would need to know, up to wich year I could reuse the gears in my 74 8-1/4"? How many spline there was in the earlier version?
 
The axle spline count went from 27 to 29 in 97. If your rear end currently has 2.45 gears then you will need to get a new carrier in order to go to numnerically higher gears (2.76, 2.94, 3.23, 3.55, etc).

As you go numerically lower in ratio the ring gear gets thinner. For Ma mopar to offer the 2.45 gear they couldn't go thinner so the carrier was machined differently to accept a 2.45 ring gear that is thick enough to have the needed strength.

Randy's has an 8.25 limited slip center section on sale for $189 right now. If you are going to go through all the work to swap ratios might as well go for the limited slip too.
 
JLP said:
The G.C. gets a 9 1/4, the same as the Durango has.
Click to expand...

Don't know about G.C's but 1st generation Durango's just like the Dakota could have an 8.25 or 9.25 depending on the engine. The 2nd generation Durango and the 3rd (or 4th depending on whom you talk to) generation Dakota now only use the 8.25 regardless of engine. The 9.25 is no longer used in any application. The bigger pick-ups are using an axle from American Axle.
 
I believe the week point on the 8 1/4 is the same as the 7 1/4. The C clips holding the axles in place.
 
The vast majority of automotive axles use C-clips to retain the axle and the c-clip or the end of the axle where the c-clips sits seldom fails. The issue with a c-clip design is if the axle it self breaks outboard of the splines and c-clip which then means there is nothing retaining the end of the axle and wheel and they will come off. If that is a concern there are kits availble that elminate the c-clip and retain the axle out at the end so the wheel won't come off.

The weak point in the 7.25 axle was the carrier and specifically the spider gears. The few 7.25 axles that were delivered with sure grip differentials were substantially stronger.

My understanding of the 8.25's weak point is the housing will deflect resulting in bearing failure or allowing the gears to seperate resulting in gear failure. This can be improved substaintilly with a cast cover that has jack screws that support and stabilize the carrier bearing caps.

I have seen articles that 8.25's with better axles, a strong diff, careful assembly and one of the support covers will survive behind 600 hp small blocks.
 
yeah i think the 8 1/4 axles are pretty good for the price, mine has survived for 5 years on the street first behind a pretty quick 318 and with more smokey bournouts than most people can even imagine, and the last two years behind a pretty high horsepower 340!
had another 8 1/4" rear for a short time with some 4.10:1 gears that blew out the ring gear on the street on hot and nice M/T tires but i think that with a one of those cast suport covers and properly put togheter it will last very good on the street!
 
dgc333 said:
Don't know about G.C's but 1st generation Durango's just like the Dakota could have an 8.25 or 9.25 depending on the engine. The 2nd generation Durango and the 3rd (or 4th depending on whom you talk to) generation Dakota now only use the 8.25 regardless of engine. The 9.25 is no longer used in any application. The bigger pick-ups are using an axle from American Axle.
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Correct on the Durangos. But your backwards on the Daks. The 1st and 2nd gen Daks never used a 9.25. Only axles available for them was a 7.25 or 8.25. 3rd gen Daks used either a 8.25 or 9.25 depending on which engine used. My 02 Dakota has a 9.25 behind the 4.7

My old 93 Dak had the 8.25 and it held up very good. I bought the truck new and put 90,000 very hard miles on it. Numerous runs down the 1/4 in the mid 14's at 94 mph and pulling a car hauler loaded to the hilt. You name it. It didn't do bad. Last I knew of the guy I sold it to was pulling a stump grinder with it and it has nerly 120,000 miles on it now and still going strong.
 
Wasn't to clear there, I was refering to the Dakota generation equivalent to the 1st gen Durango. Also, depending on whom you talk to your 02 like my 99 are refered to as either Gen 2 or Gen 3. In anycase 97 through 04 Dakota's came with either 8.25 or 9.25's. Prior to that they had 7.25's or 8.25's.

BTW, I put 256,000 miles on my 89 Dakota 4x4 with an 8.25. The rear end (or the whole drive train for that matter) never gave me any problems. I currently have about 105,000 on the 99 Dakota 4x4.
 
dgc333 said:
Wasn't to clear there, I was refering to the Dakota generation equivalent to the 1st gen Durango. Also, depending on whom you talk to your 02 like my 99 are refered to as either Gen 2 or Gen 3. In anycase 97 through 04 Dakota's came with either 8.25 or 9.25's. Prior to that they had 7.25's or 8.25's.
Click to expand...

Ok Gotcha Dave.

What threw me was I've never heard anyone call a Gen 3 Dak a Gen 2 just because it is the style of a Durango. They must be grouping Gen 1 and 2 together like they're the same which they're really not. Whole lot of differences there.
 
The only real difference in the 87-91 and 92-96 is the curved radiator support (plus the slight sheet metal changes to accomodate it) that made a couple of extra inches of room to fit a v8.
 
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