2.45 gears??

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qwk dust

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The little tag on the rear end of my '74 Duster says 2.45. I can't believe that is a gear they would put in a 318 automatic car. I have never even heard of that gear. Has anybody ever heard of that gear? It is an 8 1/4 with a 2852905 case if that matters..Thanks
 
Thanks for the reply..And people wonder why the poor little teen cars had such a bad reputation for being underperformers. Oh well, I guess it doesn't matter for my purposes since we are going to be installing a new sur grip unit and either 3.91 or 4.XX gears. No wonder the little rascal felt so anemic.
All of this will make it that more fun when we get done and she approaches 400hp with an appropriate stall and the gears. Pick on the little baby teen then..LOL. As always thanks for all the FABO help I have been receiving on this Duster project!!
 
I replaced the rear in a 80 Mirada I had with an early b body 8 3/4. The original gear was 2.20! Yes it was a dog.
 
My 74 Duster has the 2.45 in an 8 1/4. It gets me 2,500 rpm at 65mph and around 16 MPG with a Edelbrock 600. I drive it to work everyday.

My 75 Dart with an 8 1/4 also had these gears till I put in the 4.10's.

I still have them (the 2.45's) if anyone wants them.
 
The 2.45 and lower gears have a different carrier. To do to a 4.10 you will need a new differential.

FWIW, I have 3.55 gears and an A833OD in my 68 Barracuda. The 360 gives me 17-18 mpg around town and 21-22 mpg on the hiway and still runs mid 13 sec at over 100 mph. 70 mph is a tick over 2000 rpm.
 
What exactly is involved in going from the 2.45 to 3.91 etc as far as additional parts/work is concerned. I will be buying a new sur grip unit anyway since the one in the car is an open diff. Is there more I need besides the gears and sur grip unit? Thanks for the help.
 
Bearings for the diff and pinion. Best bet is to get a master install kit at the same time you get the diff and gears.
 
Why so surprised it only has 2.45's..it's only a 318 car..
 
Well, 2.45's in a 318 car would make (does make) it pretty sluggish around town which I would think is where most of the economy type Duster were driven. I would think 3.23s would, at a minimum, give it a little pep. My only two other mopars ('70 T/A Challenger and '70 Cuda) both had more gear (3.93/3.55) although they obviously were more performance oriented. It just seems 2.45 is pretty anemic for an already somewhat anemic set up. It is all good. She will be a good bit more peppy soon.
 
The 3:23 gears will pep it up allot. I had 2.45 gears in a 70 Chevelle back when I was a kid and it was a real dog. I swapped in a 3:23 rear out of a GTO and it was like night and day. Went from running 18.80's to running low 15's.

I think they put in the
 
MY BUDDY IN HIGH SCHOOL HAD A 74 DUSTER 318 AUTO PS PB AC WITH THE 2.45 GEAR BUT IT WAS IN A 7 1/4 DIFF ??? BUT MY 73 DUSTER 225 AUTO AC PS CAR HAD A 3.23 GEAR WITH A 8 1/4...!!
WEIRD..
I WOULD HAVE THOUGHT ALL THE V-8 CARS WOULD HAVE GOTTEN THE 8 1/4:wack:
 
My '74 had 2.45s in a 9 1/4. It orginally had a slant 6 with a three-on-the-tree. It had a 318 in it by the time I got it. But, like others have noted, this was pretty sluggish. So, I pumped up the engine with the Edelbrock Performer Package and low-geared 4-speed. Holy crap! I had no problem smoking the tires after that. I could start off in second if I wanted to. I could fly on the highway and still get good gas mileage (over 25 MPG averaging 75 MPH. And it still had so much power at the top end. At 90 MPH, I could accelerate like I had been doing 35. Even at 4000 RPM, at which point I was doing well over 100 MPH, I still had lots of pedal & power left.

It's a good combination for my vote.
 
The main reason these new cars have any pick up is mostly the gearing from the transmission. 2 overdrives ratios means it can be geared great at lower speeds yet at high speeds turn few rpm's

There wasn't auto overdrive trans back in the 70's so in went 2.45 gears on many cars so the fleet of cars would pass smog and mileage rules. Cars with towing packages had better gears, 3.21's
 
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