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Old 02-09-2010, 08:10 PM
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What size rear-end

I have a 1955 Chevy Convertible that I'm in the process of restoring. I put a Chevy 350 motor in with a 700r4 transmission. My tire size are 25" tall(P215 60/R16) any suggestions or web. sites I can go to to find the right type of rear end I should use. I have a 323's in now and it takes for every to shift. Would like to have something that is a little bit more responsive. Thanks for you help

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Old 02-09-2010, 09:28 PM
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Do you meen complete rear end or just a gear change?

Ok, just for the he-- of it I did some calc's, I'll assume you meant new gears. With the 700R4 and a 26" tire @ 70 mph...3.50 gears = 2216 rpm....3.73 gears = 2361 rpm.....4.11 gears = 2602 rpm. Now I don't know if anyone makes those gears sets for the old chevy rear but it gives you some idea where you would be...good luck.

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Old 02-09-2010, 09:50 PM
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Quote:
Originally Posted by 327NUT
Do you meen complete rear end or just a gear change?

Ok, just for the he-- of it I did some calc's, I'll assume you meant new gears. With the 700R4 and a 26" tire @ 70 mph...3.50 gears = 2216 rpm....3.73 gears = 2361 rpm.....4.11 gears = 2602 rpm. Now I don't know if anyone makes those gears sets for the old chevy rear but it gives you some idea where you would be...good luck.
Thanks alot. I was thinking on those lines. There was a 411 rear-end on e-bay(3rd Member) for around 220.00 which included shipping but I'm going to look around at swap meets there are getting harder and harder to find. I can buy a new ring and pinon for 150 and my friend can set it up for me. Might go that route. Tomorrow I'm goings to go in my truck and go 70 mph and see what I'm taching and make that chose. thanks again Nick
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Old 02-09-2010, 10:28 PM
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Does your truck have a 26" tall tire???? tire diameter makes a big difference. The 700R4 has a 3.06 low gear, with a 4.11 rear gear set your little old convert will have a great hole shot...but will just loaf along at freeway speeds.
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Old 02-10-2010, 01:14 AM
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I'd be a little suspect of the OEM '55 rear end with the 350 and 700r4. They aren't the strongest that's for sure. I had a 283 283 hp FI 4 spd that I wasted a number of rear ends with less tire than we have today. Broken axels, ripped R&P, blown spiders, broken caps, ripped pinion right out of the case just to name the common failures. Your 350 with 300-325 hp will have a lot more torque than my old 283 could ever dream of, especially at low rpm.

You will have more gear ratio with a 4.10 and 3.06 low gear than I had with a 5.38 and 2.20 low 4 spd. This was a good axel buster if the spiders didn't break first. Even with a good positraction you can still break parts.

If you promise to use some kind of traction bar and limit the standing starts to once in a while close to home, (walking dist) you can probably get away with 4.11. 3.55 was the standard gear and with your low gear it is pretty close to a 4.56 and a 2.2 low. It will still give you a good kick.

Best bet will be to have a spare pig and axels. If I'm not mistaken there is a 10 bolt that is close to a bolt in. Maybe from a Nova. I think it would be a bit stronger if you get after it occasionally.
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Old 02-10-2010, 06:59 AM
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I guess I can understand that folks want to keep an OEM differential. I worked may way through college (as well as via the GI Bill) in a garage. We generally did a change out of Tri Five Chebbie rear gears about once a month - and that was with 283/327 motors. They do not have a good life expectancy with more horsepower. A 10 bolt or better yet, a Ford 9" will guarantee better life expectancy. Of course, I do favor the Ford as it has ratios (and Equalocs) from the low 2's right up to the 7's with literally dozens of choices between where you can tailor the "sweet" engine RPM with performance. The width is no problem with dozens if not hundreds of people building these differentials to your specs. You also have good brake upgrades from the OEM ho-hummers - either the Ford drum or many disc selections. Cost wise - it might be a bit high to begin with, but after shedding a few sets of gear teeth - much better then a wash. (heck - even a Ford 8" will outlast a Tri Five Chebbie )

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