Cruising RPMs?

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arunice
Posts: 24
Joined: Thu Jan 25, 2018 10:02 am

Cruising RPMs?

Post by arunice »

What rpms are you all seeing when running at about 55mph? I want to determine if mine is not shifting to 3rd. I feel only 1 shift when taking off in green dot mode. 1963
Cliff Rankin
Posts: 318
Joined: Tue Jan 20, 2015 12:24 pm

Re: Cruising RPMs?

Post by Cliff Rankin »

I don’t have a tach on May 63. My work car (for now ) is an
05 Town Car. So compared to it a little. With the high rear end gears the 63 has ,70 Is comfortable. 1st is a little short , 2nd , you would definitely know it if it did not come out of 2nd by...40?
Count your gears as they shift during moderate acceleration from a light. I can’t smoke tires , but I can
Do a loud peel out and tell the mad Honda next to me he’s number 1. Does that help any ?
Aaron65
Posts: 107
Joined: Mon Oct 22, 2018 10:48 pm

Re: Cruising RPMs?

Post by Aaron65 »

My only car with a tach is my '65 Mustang, but it would have similar overall gearing (when taking tire size into account) to my '63 T-Bird. At 55, you're looking at about 2500 rpm or so in high gear. In second, you would be getting up toward 4000 rpm, which you'd certainly notice.
1963 T-Bird Hardtop
1965 Mustang
1965 Skylark
1965 Corvair Monza
1965 Dodge Dart wagon
1953 Buick Special Riviera
1974 Firebird Esprit
MN63Tbird
Posts: 223
Joined: Mon Nov 02, 2015 12:38 am
Location: Minnesota

Re: Cruising RPMs?

Post by MN63Tbird »

arunice, If you start in the small green dot Drive you will have only one shift since in that gear you start in second. In the Large Green Dot Drive you will shift through first gear to second around 20 MPH and second to third around 40 MPH. If you do not hear the transmission shifting the first thing I would check is the vacuum to the vacuum modulator on the transmission. The hose and modulator have rubber parts that get old and brittle with age. The hose goes from the modulator unit mounted on the bottom outside of the transmission to the vacuum supply at the engine . The vacuum line can be hooked to the Brake booster or to the plate under the carb. You can disconnect it and test for a good vacuum. When Hooking up a vacuum to the line it and the modulator should hold 18inches of vacuum. If not then the hose or the bladder in the modulator is bad. Ensure you have a good tight fitting on the hose when hooking it back up. The modulator is relatively cheap but it is a little pain to get to and remove.

With respect to the rpm at cruising speed. That rpm depends on your tire size and the rear gear ration. Most likely your Tbird has a 3.00 to 1 rear gear ratio. As mentioned in another thread the 64-66 mustangs have gear ratios of 2.83 to 4.11 and one option does have a 3.0. I have attached a table for speed tire size and RPMs to give you an idea. As you see when you change to Radial tires the tire diameters are slightly smaller. This will cause your speedometer to read higher than you are actually traveling.

MN63
Attachments
Effect of Tire sizes  800.jpg
1963 Thunderbird Hardtop
1966 Mustang Coupe A code
arunice
Posts: 24
Joined: Thu Jan 25, 2018 10:02 am

Re: Cruising RPMs?

Post by arunice »

Thank you for your help. I'll see what I can find now from your advice.
arunice
Posts: 24
Joined: Thu Jan 25, 2018 10:02 am

Re: Cruising RPMs?

Post by arunice »

Update- I can't tell its shifting 3 gears at all. In L it certainly is low. Both green dot and white dot shift the same. The car feels like a 2 speed oh well, Rpms at 55mph is about 2000. Good enough for me. Thanks guys.
Cliff Rankin
Posts: 318
Joined: Tue Jan 20, 2015 12:24 pm

Re: Cruising RPMs?

Post by Cliff Rankin »

Pull the air cleaner and look at the throttle linkage
I believe your car has kick down linkage for the transmission, make sure it’s All the way up.
Something simple to check.
Cliff
arunice
Posts: 24
Joined: Thu Jan 25, 2018 10:02 am

Re: Cruising RPMs?

Post by arunice »

Will do. Thanks.
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