8.25 gear swap ??
#75275
06/17/08 11:05 PM
06/17/08 11:05 PM
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Joined: Jan 2005
Posts: 12,478 Kalispell Mt.
HotRodDave
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Kalispell Mt.
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I have a 91 dakota with 3.55 gears in the original 8.25 and I want to put in something higher like a 2.94 or even 2.45 what year rears can I get gears from and how hard are these to swap in? Do I need any special tools for settin up the gears?
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: 8.25 gear swap ??
[Re: mopowergtx]
#75278
06/18/08 09:55 AM
06/18/08 09:55 AM
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Joined: Feb 2003
Posts: 4,204 Fort Worth, TX
Clair_Davis
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master
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Fort Worth, TX
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I think only the spline count (and associated parts like side gears, spider gears, diff case) changed for the 97 model year, but the ring and pinion gears SHOULD all interchange. IIRC, the truck gears were slightly larger at 8-3/8 vs. true 8.25, but it SHOULD all work. I think as long as you're swapping the whole diff chunk, any housing should be fine. The differential had to be changed on the 2.45 gears to put some meat back in to the ring gear, as the pinion is so large the ring would be too thin otherwise. There were some NOS 2.45 SG's on epay a couple years back, so that supply still seems to be out there. May as well put some good stuff in if you're doing that surgery. I also hope most of the driving will be highway, as 2.45's are anti-mileage gears around town. BTDT.
Clair
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Re: 8.25 gear swap ??
[Re: Clair_Davis]
#75279
06/18/08 11:22 AM
06/18/08 11:22 AM
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Joined: Jan 2005
Posts: 12,478 Kalispell Mt.
HotRodDave
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I had 2.45s in my 68 dart 4dr with a 273 and it was fine and my grandma had an 80s fulsize with 2.94s and quite a bit taller tires and the 318 was just fine in there also. Either way I think I will be OK with the gear ratios, this is not a hot rod. If nobody buys my cudas 318 it may end up in here some day and it has lots of tq at low rpms.
As far as the swap thing am I understanding right that one of the 2.45 SGs should bolt right in?
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: 8.25 gear swap ??
[Re: Clair_Davis]
#75281
06/18/08 11:02 PM
06/18/08 11:02 PM
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Joined: Jan 2005
Posts: 12,478 Kalispell Mt.
HotRodDave
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The trans has low gears in it, that should help it a tad.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: 8.25 gear swap ??
[Re: HotRodDave]
#75284
06/19/08 12:41 PM
06/19/08 12:41 PM
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Joined: Jan 2005
Posts: 4,525 Michigan
MarkZ
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Michigan
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Maybe you could swap an early A500 into it? The OD would give you 2.45 on the highway and you could keep the 3.55 gears for city driving.
Last edited by MarkMullins; 06/19/08 12:43 PM.
1987 Fifth Avenue - 512/518/D60
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Re: 8.25 gear swap ??
[Re: MarkZ]
#75285
06/19/08 02:27 PM
06/19/08 02:27 PM
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Joined: Jan 2005
Posts: 12,478 Kalispell Mt.
HotRodDave
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Now you guys are going to think I am nuts but the truck does have an A-500 in it. I still don't like the RPMs it runs at 80mph. The factory tack shows a 4500 redline and it ain't got no guts when it gets there. Low rpm response it great.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: 8.25 gear swap ??
[Re: Clair_Davis]
#75290
06/19/08 11:25 PM
06/19/08 11:25 PM
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Joined: Jan 2005
Posts: 12,478 Kalispell Mt.
HotRodDave
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With a 318 X 2.45 X .69 I will displace 537 cubic inches of air every revolution of the wheel.
If the truck had a 2.5 4cyl with 3.55 gears and no OD it would displace about 532 cubic inches of air per revoultion of the wheel. Some dakotas were equiped this way and I used to drive one and it was ok.
In first gear it would be a different story.
318 X 2.74 1st gear X 2.45 rear gear = 2134 cubic inches per wheel revolution.
150 X 2.74 ist gear times 3.55 rear gear = 1459 cubic inches per wheel revolution.
I would have a lot more tq to accelerate than the 4cyl but cruise displaceing the same amount of air and coresponding fuel as the 4cyl. I would probably get a custom cam ground for it to boost the tq at very low rpm to further help it cruise better.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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