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?

get a hold of a service manual, and look the procedure over. I have a 2.45 limited-slip i plan on pulling out soon let me know.

2.4 gears and down have a different sure grip and carrier. The 2.7's and up are all the same. Then in the late 1990's they changed ring gear styles and carrier I believe. Different ammount of bolts maybe. Cant remember exactly but just be aware of this when looking for gears and sure grips. So for example a Dakota up to the point they changed the guts inside the 8 1/4's could use rear gears out of any 8 1/4 Mopar they made up to that point. So JY cars should a good place to find a set of 2.94's if thats what you want you gas miser Dave.

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

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 think the differential is the magic part needed to run 2.45's, so if you've got one of those you're good to go. I don't think those 2.45SG's sold for very much, as it's not a popular gear ratio and the diffs weren't good for anything else.

My 74 Swinger with 2.45's got 10-12mpg in town, but 20+ on the highway. The 2.45 1st gear in the 904 just didn't multiply torque enough for the pig to get out of her own way. Out on the open road, she was actually kind of fun to drive. 2nd gear would go a LONG way...

Clair

The trans has low gears in it, that should help it a tad.

Most people ship them to you for the cost of shipping. I just don't want to toss mine in the scrap if some one can use it. I'm going to 3.73's on a fresh limited-slip.

OK you got me. Let me know when you have it ready to go and I can send some $ for shipping and lunch or

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.

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 definately a left lane driver mabey not 100 but few people ever pass me. I don't think in town mpg will be any worse than my old dart was with 2.45s with it's open chamber low compresion heads and a carb. I am not much of a jack-rabbit in the truck because stuff would roll all over in there and spill... but I will roll on down the highway a lot and um right up to but never over the limit

My 90 dak had a 360 magnum with an A-500,when the original 7 1/4 broke I installed a 2.94 ratio 8 1/4 rear. It was great on the highway,but even I think 2.45 gear would be just to far without a major torque lump under the hood.

One of my previous combos WAS 2.45 cogs with an OD 833. I was trying to eek some mileage out of my tired 360 with a Summit/SSI 204/214 cam. It made no better mileage in OD than 3rd, although it did lug down the road at 65-70 OK. Basically had to downshift every time you needed to pass, though.

Clair

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.

It'll be interesting to see if it works out that way. It may have just been a function of my tired 360, but no combo I ran netted better mileage at 65-70mph. Thtottle position plays in to how much air/fuel is getting in to the engine, so I think the lower mechanical advantage of the OD was forcing a deeper throttle and drop in potential mileage. The joys of driving a brick...

Clair