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rear end gears for my 71 Demon
https://slantsix.org/forum/viewtopic.php?t=24502		 Page 1 of 1
Author:  71_demon [ Fri Aug 17, 2007 8:47 am ]
Post subject:  rear end gears for my 71 Demon
Hi All,

I searched the archives and couldn't find the answer so here goes.

I have a 71 demon 225 slant six. I have parts to convert it over to the super six. I would also like it to grab a little more out of the hole and I read some where that rear end gears can help.

Finally to the questions. Is there a better gear setup for the demon than just the stock? And is it something I can find in the junk yard? Finally, is there a setup that I can just change the gears out or do I need to swap the drive shaft etc..?

I know its not asking for to much to have a pull and swap :lol: but you never know until you ask.

Thanks

Jeff

If you always do what you've always done, then you always get what you always got.
Author:  Romeo Furio [ Fri Aug 17, 2007 4:58 pm ]
Post subject:  demon
Utah should still have some old 60's Darts and Valiants in the wrecking yard. My 63 Valiant has 3.23's my 67dart had 2.93's. Your car may have 2.93 or 2.76. Randys ring and pinion may have as deep as 3.91's.
I am assuming your car has a 7.25" rear axle. If you are lucky you may even find a sure grip.
Author:  Ron Parker [ Fri Aug 17, 2007 6:22 pm ]
Post subject: 
Look for a 60ths dodge van Slant six. they were common so was the pick up trucks. Slant six. Most trucks and vans came with either 3.55 gears or 3.91 gears With the Slant engine. Look on the door post and it will show you the gear ratio. Doint matter if it is a 741 case it will bolt right up to a 742 or a 489 case. Probaly get the whole rear end for fifty dollars.
Author:  71_demon [ Fri Aug 17, 2007 6:55 pm ]
Post subject:  Awesome stuff guys
great stuff guys, So which set should I look for to have the demon grab a little more??

Thanks for the info.

Jeff
Author:  Joshie225 [ Fri Aug 17, 2007 8:03 pm ]
Post subject: 
Your car if it's an automatic probably has 2.76 gears so anything numerically higher will improve acceleration. 3.23 is about as high as I would go for a stock slant. Having more RPM available or a taller tire will support/require numerically higher gears. It's probably going to be tough to find 7 1/4 rear end gears numerically higher than 3.23 used. Look for Dakota 4 cylinder pickups and check the decal under the hood to see if you can get something decent. Otherwise...

http://www.drivetrain.com/chrysler7.5.html
Author:  71_demon [ Sat Aug 18, 2007 3:06 am ]
Post subject:  What about the speedometer
Got some great info and can't wait to do one of my favorite hikes through a junk yard in Grantsville Utah.

I'm curious though if I switch to a different gear ratio how will it affect my speedo?
Author:  Rug_Trucker [ Sat Aug 18, 2007 7:00 am ]
Post subject: 
Mine cruises comfortably all day at 80 with 3:23's.
Author:  Jeffc [ Sat Aug 18, 2007 12:55 pm ]
Post subject:  Re: What about the speedometer
Quote:
Got some great info and can't wait to do one of my favorite hikes through a junk yard in Grantsville Utah.

I'm curious though if I switch to a different gear ratio how will it affect my speedo?
Yes, a differant ratio will change how the speedo reads.
If you find a doner 904 with the gears you want in the rear end
just grab the speedo gear out of the trans to match the rear end.

Randys is a good place to start for a new ring and pinon (there are other sellers, but mamopar is very high price), your going to want to
check your spider gears for slop--- spiders are the real weak link
in a 7.25 axle and there not that much money to replace if the
center chunk is already out of the axle......

Dekotas in the 80s have the 7.25 alxe and are pretty common.
D100/150 trucks will have 8.75 or 8.25 depending on year
and are not compatable with the 7.25 axle.

3.23 is a pretty good all around gear set for a stock application
904, but about as low as I would go, unless you what stop light
to stop light action and don't care about freeway driving, then
3.55 would be better.
You may have the 2.94 or 2.76 (aprox numbers) now.

There are axle differances with the gear sets, not all can be swapped
gear set for gear set. You really need to find out what your
gear ratio is in your 71 before setting out to find a set to swap in
unless your going after the hole axle.
This would come up if you have the 2.76 gears now, then a axle
case swap would be needed.
Author:  65 dartman [ Sat Aug 18, 2007 3:47 pm ]
Post subject: 
Quote:
Look for a 60ths dodge van Slant six. they were common so was the pick up trucks. Slant six. Most trucks and vans came with either 3.55 gears or 3.91 gears With the Slant engine. Look on the door post and it will show you the gear ratio. Doint matter if it is a 741 case it will bolt right up to a 742 or a 489 case. Probaly get the whole rear end for fifty dollars.
Author:  65 dartman [ Sat Aug 18, 2007 3:52 pm ]
Post subject: 
Quote:
Quote:
Look for a 60ths dodge van Slant six. they were common so was the pick up trucks. Slant six. Most trucks and vans came with either 3.55 gears or 3.91 gears With the Slant engine. Look on the door post and it will show you the gear ratio. Doint matter if it is a 741 case it will bolt right up to a 742 or a 489 case. Probaly get the whole rear end for fifty dollars.
Clicked too soon :oops: Ron is absolutely correct. In my 69 A108 with slant 6 and 3 on the tree, the rear end gear is a 3.91 (non-SG). Parted out a 72 D100 with 318 and it had a set of 3.23's in it (both 8 & 3/4s)
Author:  Jeffc [ Mon Aug 20, 2007 12:29 am ]
Post subject: 
Quote:
Quote:
Quote:
Look for a 60ths dodge van Slant six. they were common so was the pick up trucks. Slant six. Most trucks and vans came with either 3.55 gears or 3.91 gears With the Slant engine. Look on the door post and it will show you the gear ratio. Doint matter if it is a 741 case it will bolt right up to a 742 or a 489 case. Probaly get the whole rear end for fifty dollars.
Clicked too soon :oops: Ron is absolutely correct. In my 69 A108 with slant 6 and 3 on the tree, the rear end gear is a 3.91 (non-SG). Parted out a 72 D100 with 318 and it had a set of 3.23's in it (both 8 & 3/4s)
All very true, but a truck axle will not bolt to a A body without mods
and none of the 8.75 stuff is compatable with a 7.25
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