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| 7 1/4 rear revisited https://slantsix.org/forum/viewtopic.php?t=13176 |
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| Author: | Murch [ Sun May 29, 2005 4:23 am ] |
| Post subject: | 7 1/4 rear revisited |
So I found out I have a 2.93 rear. It seems according to my research a 3.23 would benefit my applications. How difficult is it to do? Also does anyone know about part #'s for this and where I could find these reasonably priced ? Thanks, Dale |
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| Author: | SlantSixDan [ Sun May 29, 2005 7:12 am ] |
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The effort and expense involved in changing from 2.93 to 3.23 may not be worth the benefit gained—what are you hoping to achieve? There's not a whole huge lot of difference between 2.93 and 3.23 (it's 10% shorter). To put this into real terms, if you were running P205/70R14 tires, your engine speed at 60mph would be 2574 rpm with 3.23s, and it would be 2335 rpm with 2.93s. That's a difference of just 239 rpm—scarcely detectible from the driver's seat. Regarding the cost, it's highly variable. If you find a 3.23 rear axle in good condition and swap it in, the cost is only your time and effort plus whatever repair parts the new rear axle needs (oil seals, brake parts, gasket, etc.). On the other hand, if you're thinking of rebuilding your rear axle with a set of 3.23 gears, the parts and labor cost goes way up. 3.23 ring-and-pinion sets are still available from Chrysler, for a variant of the 7-1/4" rear axle was used on light-duty Dakota pickups. |
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| Author: | Murch [ Mon May 30, 2005 12:49 pm ] |
| Post subject: | |
When I purchased my Dart, I drove it to Illinois from Colorado doing about 80-85mph. I averaged around 22-24mpg (with a/c). It about floored me (obviously good). The majority of my driving is about 30-50 mph and stop and go. By what I've read the larger gear may inhance my around town mileage and "fun factor". If it was reasonable (the price of the parts) I thought it may be worth my time. I've been getting around 18-20mpg. I'm still tweeking (which I'm certain the majority of the people on this sight never stop) but I'm thinking by sound of it, it may not be worth it. Besides I'm bit by the bug and probably will keep continuing to "improve" what I have and might eventually get an 8 3/4. Thanks, Dale |
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| Author: | SlantSixDan [ Mon May 30, 2005 1:33 pm ] |
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Quote: When I purchased my Dart, I drove it to Illinois from Colorado doing about 80-85mph. I averaged around 22-24mpg (with a/c).
That's suspiciously good.What year is this car? Which engine? Which transmission? Which carburetor? And what rear axle? Have you, er, checked the speedometer for accuracy? Sounds like it may well be running fast... |
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| Author: | NewLancerMan [ Mon May 30, 2005 1:56 pm ] |
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Dale, if you're going to do the 8 3/4 eventually anyway, just save your money now. Or, you could get a slightly smaller set of tires and that would be the same as regearing. Maybe you can find someone to borrow from and give it a try? MJ |
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| Author: | Murch [ Mon May 30, 2005 2:36 pm ] |
| Post subject: | |
1964 Dodge Dart, original 170ci, bbs, 904 and I believe to be a 2.93 rear. No I haven't checked the speedo for accuracy. If there is tracking error I'm not that concerned (for a 40+ year old car to come close to matching our other car -01 Acura TL), and I'm not complaining. By the way I'd much rather drive the Dart. It has 60k on it. Also I currently have little 185 80 13 weenys on that don't do a whole lot for handling, but apparently help with the mpg. I think I'd prefer the trade off of mileage for better handling. I think I've decided to nix any further work on the rear. I had a 66 Dart (mint) with a 225 with 39k on it and remembered getting 22mpg on it (I was out of work and had to sell, before you start condeming me), that was also conservative driving. Does these figures seem too high? Thanks, Dale |
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| Author: | SlantSixDan [ Mon May 30, 2005 3:10 pm ] |
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Quote: 1964 Dodge Dart, original 170ci, bbs, 904 and I believe to be a 2.93 rear.
That'd be a bit of a strange combo; I'm fairly sure the factory spec w/170 and auto was 3.23 (2.93 with 225). But I could be wrong for '64, and a 170/2.93 combo would indeed be a good mileage-maker. Still 24mpg @ 85mph w/the A/C on seems suspiciously high.Quote: No I haven't checked the speedo for accuracy. If there is tracking error I'm not that concerned
My point wasn't so much related to whether the indicated speed is accurate, but to the odometer readings as they apply to your MPG calculations.Quote: I had a 66 Dart (mint) with a 225 with 39k on it and remembered getting 22mpg on it
Possible on a stock automatic Dart with a nice, fresh engine, skinny tires, conservative driving and an altitude at or below sea level.
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| Author: | Murch [ Mon May 30, 2005 3:39 pm ] |
| Post subject: | |
Oh. Yes it was pretty much (as traffic and police permitted) 70-85 mph up and down, but with a long stretch through the heartland-oh so flat and boring at 85 mph. The highest recorded was 24 mpg the lowest 21mpg. I did use premium and name brand gas. I drove about 1200 miles, hows that for trust in slant six, sight-unseen purchase (more like dumb luck and a trust for another fellow Mopar enthusiast). By the way for you wise guys---- don't try to sell me an NOS Mopar bridge or swamp land! I'll try the rear end trick again, maybe it does have a 3.23- I was babysitting a posse at the time. Thanks, Dale |
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