Mopar 8 3/4 VS 8 1/4

Phillip marvetz · 10-06-2009, 10:26 AM

Can I expect a gain in ET buy switching from one to other if using the same gear ratio? How about overall weight?

John Dinkel · 10-06-2009, 10:58 AM

8 1/4 will be easier to break.

treessavoy · 10-06-2009, 11:12 AM

I broke an 8 1/4 with a warmed over slant six and a 4 speed but it was not a posi unit. With a locker and aftermarket gears it might live behind an automatic but in my opinion it's not worth the weight savings,

JimR

Jim Wahl · 10-06-2009, 12:18 PM

Not worth the trouble! You *will* break the 8 1/4 ! Jim

Todd Boyer · 10-06-2009, 02:17 PM

I read a long time ago that Bob Lambeck ran an 8 1/4 in a Duster 360 stocker but I don't know how long it lasted...

Eric Merryfield · 10-06-2009, 02:38 PM

Quote:

Originally Posted by Todd Boyer

I read a long time ago that Bob Lambeck ran an 8 1/4 in a Duster 360 stocker but I don't know how long it lasted...

Does anyone or did anyone make a spool for a 8.25? I don't think so, but I could be wrong. If you do go the 8.25 route, you will have to get the right suregrip unit to fit your application. I have a NOS one in the garage since I bought two for my warlock just in case I needed it.

Axles are another concern here too. Not sure how strong the factory original units were/are after 25 and more years.

Eric

Todd Boyer · 10-06-2009, 04:03 PM

Quote:

Originally Posted by Eric Merryfield

Does anyone or did anyone make a spool for a 8.25? I don't think so, but I could be wrong. If you do go the 8.25 route, you will have to get the right suregrip unit to fit your application. I have a NOS one in the garage since I bought two for my warlock just in case I needed it.

Axles are another concern here too. Not sure how strong the factory original units were/are after 25 and more years.

Eric

Eric, does your Dakota have an 8 3/4 in it?

bsa633 · 10-06-2009, 06:56 PM

Quote:

Originally Posted by Eric Merryfield

Does anyone or did anyone make a spool for a 8.25? I don't think so, but I could be wrong.

I know some that made a spool themselves back in the days and got it to last a long time in a 360 duster stocker...but it finally gave in and had to leave room for a 8.75..the gear selection isn't very good...a 4.56 looks like "top of the line"!

MontyC · 10-06-2009, 06:57 PM

I ran a 8 1/4 for years in a 72 Duster 340. Broke one tooth once on ring gear. Car ran mid 11's in "stocker trim". Full interior all steel. I think it is less hassle with 8 3/4 being able to use a spool and not have to replace the Posi in the 8 1/4 every few years or so. I did change to an 8 3/4 but made a gear change so I can't say if one is faster.

Monty

GTX JOHN · 10-06-2009, 07:03 PM

I think Jim Durham ran a 8.25 in his F/SA til a couple of years 'l ago...If you equalized the weight I used to be .01 faster with 8.25 but hardly worth to trouble. I will give you a housing for free if you get my way again. PS I lost your number again.

s

10-06-2009, 10:26 AM	#1
Phillip marvetz Senior Member Join Date: Oct 2008 Location: Lynden ,WA Posts: 820 Likes: 0 Liked 3 Times in 3 Posts	Mopar 8 3/4 VS 8 1/4 Can I expect a gain in ET buy switching from one to other if using the same gear ratio? How about overall weight?

10-06-2009, 10:58 AM	#2
John Dinkel Senior Member Join Date: Nov 2005 Location: Pinckney, Michigan Posts: 500 Likes: 352 Liked 233 Times in 62 Posts	Re: Mopar 8 3/4 VS 8 1/4 8 1/4 will be easier to break. __________________ John Dinkel 3295 STK

10-06-2009, 11:12 AM	#3
treessavoy VIP Member Join Date: Feb 2009 Location: Dunnellon,FL Posts: 1,103 Likes: 0 Liked 4 Times in 4 Posts	Re: Mopar 8 3/4 VS 8 1/4 I broke an 8 1/4 with a warmed over slant six and a 4 speed but it was not a posi unit. With a locker and aftermarket gears it might live behind an automatic but in my opinion it's not worth the weight savings, JimR __________________ Jim Rountree

10-06-2009, 12:18 PM	#4
Jim Wahl Veteran Member Join Date: Jan 2002 Location: Central Florida Posts: 5,842 Likes: 627 Liked 672 Times in 121 Posts	Re: Mopar 8 3/4 VS 8 1/4 Not worth the trouble! You will break the 8 1/4 ! Jim __________________ Jim Wahl....NHRA #2239 S/SS - IHRA # 8 Stock, D2 Stock Champion (forever I guess) 2019 Baby Gators Stock Champion 2009 D2 National Open Stock Champion 1981 D2 West Palm Beach LDRS SS Runner Up Past President, Southern Stock / Super Stock Association. SSSSA Forum Moderator

10-06-2009, 02:17 PM	#5
Todd Boyer Senior Member Join Date: Feb 2004 Location: Saint John NB Canada Posts: 560 Likes: 27 Liked 6 Times in 5 Posts	Re: Mopar 8 3/4 VS 8 1/4 I read a long time ago that Bob Lambeck ran an 8 1/4 in a Duster 360 stocker but I don't know how long it lasted...

10-06-2009, 06:57 PM	#9
MontyC Junior Member Join Date: Jan 2005 Posts: 19 Likes: 0 Liked 0 Times in 0 Posts	Re: Mopar 8 3/4 VS 8 1/4 I ran a 8 1/4 for years in a 72 Duster 340. Broke one tooth once on ring gear. Car ran mid 11's in "stocker trim". Full interior all steel. I think it is less hassle with 8 3/4 being able to use a spool and not have to replace the Posi in the 8 1/4 every few years or so. I did change to an 8 3/4 but made a gear change so I can't say if one is faster. Monty

10-06-2009, 07:03 PM	#10
GTX JOHN VIP Member Join Date: Jun 2009 Location: Boulder City, Nevada 89005 Posts: 2,530 Likes: 2,222 Liked 1,809 Times in 572 Posts	Re: Mopar 8 3/4 VS 8 1/4 I think Jim Durham ran a 8.25 in his F/SA til a couple of years 'l ago...If you equalized the weight I used to be .01 faster with 8.25 but hardly worth to trouble. I will give you a housing for free if you get my way again. PS I lost your number again. s Last edited by GTX JOHN; 10-06-2009 at 07:06 PM.