1965 mustang gears..question

synthartist69 · Jan 28, 2010

Hey everyone! My 65 fastback has a 4 speed with 3:73 gears. It is really wound up at 70mph. Not sure what the rpm is at 70mph, but it feels like at least 3k. I won't be going to the drag strip, but I do want it to be a street racer. What would be the best way to get the rpms back down so that I can cruise on the interstate but still have some punch on take off? How many rpms can I drop by going with a 3:08 or 3:27 rear? What about going with a 5speed instead? My 4th gear is 1.00 as is the 4th gear on the 5 speeds. I have seen that certain 5 speeds have a .80 or .67 fifth gear. How much of a drop can I expect from one of those and how can I locate a 5 speed with the .67? All comments appreciated!

Jim

tx65coupe · Jan 28, 2010

I would recommend a 5 speed conversion or swap the 3.73 for 3.20 ish gears.

Why no tach?

gjz30075 · Jan 28, 2010

As a point of reference, I have a .68 5th gear, 3:55 diff gears and 26" tires and I turn 2100 rpm at 70 mph. It's a pretty good built 331 so, I really only use 5th from about 50 mph on.

ultrastang · Jan 28, 2010

A 3.73 rear ratio with an overdrive ratio of .68:1 would be a final drive equivilent of 2.54:1. --In 5th gear [overdrive], it would be like the rear end ratio is 2.54:1.

3.73 x .68 = 2.5364

RPM-charts

Torque Multiplication

68RCodeConv · Jan 29, 2010

I have a .62 OD with 3.89 rear gears. 2200 rpm at 70 mph.

Going to a 5-speed was one of the best things I ever did.

synthartist69 · Jan 30, 2010

68RCodeConv said:
I have a .62 OD with 3.89 rear gears. 2200 rpm at 70 mph.

Going to a 5-speed was one of the best things I ever did.

Did you initially have a 4 speed manual? If so, what were your rpms at 70mph before the 5 speed was installed? Thanks!

Jim

synthartist69 · Jan 30, 2010

68RCodeConv said:
I have a .62 OD with 3.89 rear gears. 2200 rpm at 70 mph.

Going to a 5-speed was one of the best things I ever did.

I agree, the 5 speed seems to be the way to go. If I go down from 3:73 back to 3:08 I only shave off 600 rpms at 60mph. If I go with a 5 speed and keep the 3:73 gear, I shave off about 1000 rpm at 60mph. If I could get a 5 speed out of a cobra or svo, I could shave off even more, that is if those will work. The cobra and svo have a .63 final drive whereas the other 5 speeds have a final drive of .68.

Thanks for the input!

Jim

65FBE2 · Jan 30, 2010

First of all you need a T5 tranny or it will not fit properly in a 65-66. The tranny tunnel is smaller. There are ways to make a TKO fit but for your application not worth the hassle IMHO. Get a late model 5.0 bell-housing and a custom cross member. Then you need a custom clutch pivot spacer to use your current clutch linkage or you will need to convert to a cable clutch or hydraulic set up. I've done this conversion on two cars now and it is the single best mod you can make. You get the added benefit of a lower 1st gear, making your 3.73 act more like 4.11-4.5 and the 5th gear that is O.D. Just make sure you you get a world class tranny or better yet a T5z model.

synthartist69 · Jan 30, 2010

Great advice! Is there a number on the world class or the T5Z that I should be looking for? I currently have a top loader 4 speed, with a hurst shifter. Will my shifter work with the T5? I want to have the same look on the interior as I do now with the 4speed. Thanks!

jim

Z06killinSBF · Jan 31, 2010

you can swap the handle over to the t5. The shifter itself is not the same.

woodsnake · Jan 31, 2010

Post # 23 has a lot of links for parts and other information for doing this swap.

1967 converstion to 4 speed - Page 2 - Classic Cougar Forums

65ShelbyClone · Feb 1, 2010

synthartist69 said:
If I could get a 5 speed out of a cobra or svo, I could shave off even more, that is if those will work. The cobra and svo have a .63 final drive whereas the other 5 speeds have a final drive of .68.

Actually, not all of the SVOs have a World Class T5 and none of them have .68 OD. '84 came with a non-WC T5 that had a 4.06 first gear and a 0.82 fifth. '85-86 had a WC T5 with a 3.50 first and 0.78 fifth. None of them have the same input shaft as a V8 T5.

Due to those differences and the fact that only ~9800 were made, it's not a good donor candidate.

68RCodeConv · Feb 2, 2010

Z06killinSBF said:
you can swap the handle over to the t5. The shifter itself is not the same.

Handle is not a bolt on swap. T5 shifter rods are internal so the 4-speed linkage will not work.

I bought a T5Z and replaced the delivered shifter with a Tri-Ax. Then I installed the 65-67 "stock appearing" shifter handle with a 1969 Mustang shifter boot. Looks stock, shifts great.

Z06killinSBF · Feb 4, 2010

68RCodeConv said:
Handle is not a bolt on swap. T5 shifter rods are internal so the 4-speed linkage will not work.

I bought a T5Z and replaced the delivered shifter with a Tri-Ax. Then I installed the 65-67 "stock appearing" shifter handle with a 1969 Mustang shifter boot. Looks stock, shifts great.

Maybe I am taking this wrong but, that is exactly what I said.

1965 mustang gears..question

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