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Rear End Ratio Guys on the forum are always saying they drive their cars 50 to 60 miles/hour and feel their cars are cruising.
Well, I know we are comparing apples and oranges most of the time because of the variety of mods people have done to the engine, and rear end, not to mention those who have put in over-drives. I have an an early '28 (AR) coupe which was bone stock until I put a different set of gears in the rear end a while back. (Can't remember the ratio). The car would go faster, but I still feel that 45 is the comfortable cruising speed. My '31 pu has a lower ratio rear end and feels rushed at 45. The engines in both cars run reasonably well, they just don't seem to like higher rpms. How about the rest of you that are running stockers. Is 40 to 45 still too slow for a cruising speed. Should I be looking for a problem? Running 'em harder? |
Re: Rear End Ratio I have a '29 Coupe that is all stock with the 3.78 rear end. Betsy runs good and smooth @ 45mph but she has alot of throttle left. I will run her faster if I'm holding up traffic or something, then back down to 45 when I can.
I have had her up to 60mph but I didn't like the vibrations. I had to do it just to see if it would!:D p.s. I live at 5800ft elevation. |
Re: Rear End Ratio wow, the only time my car ever breaks 55 is on a long steep down-hill in neutral. Looks like I'll have to go racing this w/e just to see if the speedo even has a 60.
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Re: Rear End Ratio my 30 coupe also cruises at 45, but will only pull 60 down hill. Put me on any grade and its down to 27 mph
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Re: Rear End Ratio 45 to 47 MPH most of the time without watching the speedo. My Tudor just seems to like that speed. I punched it up to 62 once on level ground and felt she would have gone faster but we ran out of road. Checked with a GPS.
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Re: Rear End Ratio I have a good engine w/ high compression head and touring cam. With 3:78 gears it would do 60 no problem but there was vibration and I am sure it was tough on the engine,
I installed 3:54 gears and it helped a little to ease the vibration. I have now installed a Mitchell and shift down at around 45 mph. I can cruise at 50-55 no problem and the balance of the Mitchell drive line runs smoother even when out of OD. It makes the coupe a lot more comfortable and enjoyable to drive. This is a daily driver and travels extensively. Steve |
Re: Rear End Ratio BroBrian, I think where a lot of this confusion comes is the difference between someone saying "I drive my car 45 mph." vs. someone saying "A Model A will only run 45 mph and anything faster is unsafe." If you only feel comfortable driving your car 45, then that is a perfectly acceptable speed for you. I also think your locale and driving conditions largely dictate what should be a safe speed however confidence in your car should be the utmost priority. I think knowing that your brakes and steering are within factory specifications will give you that confidence.
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Re: Rear End Ratio Brent,
Yeah, maybe, but I personally feel the car is cruising at 45. It's running with less vibration, the gas mileage is steady, doesn't overheat etc. So, it's not just a subjective thing. I've run my car up to 55, but there's no way in hell I'd keep it up for long. I'd be asking for trouble. I guess what I'm looking for could only be learned by driving another stocker that, as you say, is perfectly up to spec. in other words, "like new." If it turned out that the other car really ran so much better than mine at 55+, I'd have to conclude that my car was somehow worn and in need of help. It's just hard to imagine that other stock cars are running at that high an rpm and not being pushed to the limit. |
Re: Rear End Ratio My coupe's speedo says I am going 50 or 55 MPH-wow! But--my GPS says it is only 40 MPH or so! Looks like the old speedo needs some work.
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Re: Rear End Ratio Tom, what do you mean "wrong gear for the cable"?? Are you talking about the gear on the drive shaft? It is a 19 tooth and if I remember that checks with my rear end ratio.
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Re: Rear End Ratio Quote:
Your speedometer probably needs to be lubed and may need adjustment. |
Re: Rear End Ratio Thanks Tom. Will get around to working on it a little later. Have a number of other things to get done first.
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Re: Rear End Ratio So what is the ratio in a stock rear end? No doubt not as simple a question as it sounds. Seems my pickup is geared lower than the coupe was even before I changed it.
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Re: Rear End Ratio 3.78 is standard for the cars. Your pickup might have 4.11.
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Re: Rear End Ratio Ahh, that's why when my son and I went for a spin ( race) the other day, the car was slower off the line :) but drove right by the truck until we hit the hill. It was a dead heat on the "speed-coast" back down, however. Loads of fun, but the two A's performed very differently. Even so, neither one reached more than 52 ish.
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Re: Rear End Ratio Today I took mine out for sea trials with a stock B I just installed. Ran smooth but I kept reaching for higher gear. It really started winding up at anything faster than 45. Just about what it did with my A engine. I heard that their were different ratios for different areas of the country (mountain west vs. midwest?) and had a stamping on the banjo??
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Re: Rear End Ratio I have seen several threads disscussing "speed driven". I know most don't have tachometers,but I am wondering what RPM's these motors are running at the speeds given. What is the "perfect RPM" on these motors?
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Re: Rear End Ratio Most A's have a "sweet spot', a speed at which the car runs smooth without excessive vibration. As many have pointed out there are many reasons why. Bottom line, the car is talking to you and we should listen. Personally, I beleive that an addition of overdrive is the easiest way for higher highway speeds.
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