PDA

View Full Version : 8 1/4 rear end question


ep87
08-06-2004, 10:17 PM
I've purchased a 73-74 a body 8 1/4 open rear end for my 70 duster s6 to 318 swap, with 2.45 gears? I Think. Is there any other mopars that came with a traction lock and lower gears that
could be swaped into this housing and axle set up ?, maybe out of a dakota ?. I'd like to get into 3.55-3.90 ratio range.

dwc43
08-06-2004, 11:08 PM
Find a 318 auto Dakota and it should have a 3.55 in it. Finda 4x4 and it might have a sure grip in it. :D

Bill55AZ
08-07-2004, 09:28 AM
I have heard that it is not a direct swap when trying to change gears into the 8.25 housing that has 2.4 or 2.2 gears originally.
Someone once told me that it can be done but you are better to start with a housing that has 2.7 or higher number to start with. On the other hand, 2.45 gears in a late A body doesn't sound right, I thought that gear ratio didn't come in til later. Better check that out....

Dakotas, light duty Rams, vans will have the 8.25 in gears from 2.9 to 3.9. 3.5 is the most common, and suregrip is an option.

Something to consider, a Dakota 8.25 Axle (4.5" 5 lug from an 87 thru 90) will have the exact same distance spring pad to spring pad of 43", but overall width will be about 4 inches wider. If you have 2" to spare between sidewalls and edge of fender, you can use your existing wheels, otherwise you may have to go with a different backspace. So you could transfer an entire axle in there.
91 thru 96 axles will have the 6 lug pattern, but the axle shafts from 87-90 are a direct swap. In 97, they changed from 27 spline to 29 spline and the axle became much more durable.
4x4 axles will have the spring pad on top, tho.

ep87
08-07-2004, 08:20 PM
Thanks for the info guys
I'm not sure on the 2.45 ratio , as I have not picked it up yet that just what the wrecking yard told me. As far as the housing not accepting lower gear when originally equiped with the 2.45 or so gears I've had some people tell me the carrier was different, If any one knows for sure I'd like to know.

thanks again for all the info

dwc43
08-07-2004, 08:27 PM
The 2.45 carrier is different but the housings are not. Since you want a sure grip you will be tossing the gear and carrier anyway. You should have a 2.76 gear in it. The higher gears are not that popular. I've seen very few of them. :D

NiceRoach74
08-08-2004, 01:28 PM
The phenomenon these guys are describing is known as a "carrier break". After a certain point, it becomes physically impossible to make a single gear carrier that will cover the range of ring and pinion sets, due to the changes in dimensions as the ratio decreases (numerically). On the 8.25", the break occurs between 2.45 and 2.7x gear sets. Some people think that you have to toss the entire axle, but that's not the case.

Also look out for the old Diplomat/Gran Fury cop cars - a lot of them had factory Sure-Grip, though many were saddled with 2.91 gears.

Bill55AZ
08-08-2004, 03:28 PM
[i]Also look out for the old Diplomat/Gran Fury cop cars - a lot of them had factory Sure-Grip, though many were saddled with 2.91 gears. [/B]

not sure what you mean by saddled with here. I am a big fan of that ratio, it gives just enough extra performance without being too detrimental to economy. If I was street racing, 3.2 would be nice, but I don't do that. Most of the M body cop cars had 2.9 actually, 3.2 is very hard to find in the junk yards I visit. Most non cop cars had 2.4 or 2.2.

dwc43
08-09-2004, 02:15 AM
They've been changed then. State Trooper cars have 2.94's and no higher than 2.76. City and or county cars have 3.23's or 3.55's. Some may have a 2.94 though. :D

Bill55AZ
08-09-2004, 09:12 AM
I suppose the departments can order what they want. The 3.2 and 3.5 might make sense in a large city, but out here in AZ we have fairly high speed limits right in town. I check every cop car that comes in to my favorite junk yards and have only seen 2.9 ratio, and almost always with sure-grip. I would like to find one with the 3.2 or 3.5 tho.

dwc43
08-09-2004, 06:15 PM
Check out a V6 or V8 auto Dakota. Most of them came with 3.55's with andwithout sure grip. Most likely the 4x4's will have the sure grips. :D

ep87
08-10-2004, 02:27 PM
thanks for all the info guys, I pick up the rear end today and can find out what it has as far as gears. It sounds like my best bet would be to find a Dakota with a sure grip and 3.55 gears. Do you think this is a reasonable ratio for this car, again it's a
70 duster s6 to 318 conversion, donor car was 76 valient with 904 auto all stock except for edlebrock performer cam, mainifold, 600cfm carb, and headers.
the car is a every other day driver and will see a occasional trip to the strip.

340duster1
08-10-2004, 02:31 PM
DW43 is 100% correct on this. The 2:45 set has a different carrier but the housing is the same. I just went through all of this in an 8.25" diif for an a-body. I swapped in a set of 3:92's from a dakota and tried using a suregrip from a 2:45 gear set. It did not work. I had to get the correct suregip to get it to fit.

dwc43
08-10-2004, 10:22 PM
Originally posted by ep87
thanks for all the info guys, I pick up the rear end today and can find out what it has as far as gears. It sounds like my best bet would be to find a Dakota with a sure grip and 3.55 gears. Do you think this is a reasonable ratio for this car, again it's a
70 duster s6 to 318 conversion, donor car was 76 valient with 904 auto all stock except for edlebrock performer cam, mainifold, 600cfm carb, and headers.
the car is a every other day driver and will see a occasional trip to the strip.

On a stock cam it will turn a lot of rpms at a low speed, but that will be o.k. if it's only driven in town. It would really tax the engine on the interstates. That carb is too small too. A thermoquad would be a better choice. More throttle responsive and it was stock on all the small blocks at 800 cfm. :D

dwc43
08-10-2004, 10:23 PM
Originally posted by 340duster1
DW43 is 100% correct on this. The 2:45 set has a different carrier but the housing is the same. I just went through all of this in an 8.25" diif for an a-body. I swapped in a set of 3:92's from a dakota and tried using a suregrip from a 2:45 gear set. It did not work. I had to get the correct suregip to get it to fit.

Thanks. :D :D