Maximum rpm with an MX?

Maximum rpm with an MX?

Joined: April 25th, 2006, 1:08 am

February 14th, 2012, 3:29 pm #1

I have a 1959 MX in my 390 Galaxie. The 59 MX does not have a vacuum modulator. When I floor it I can get up to 4200rpm before the shift. What I am wondering is if I put in a more powerful cam or engine, one that is supposed to top out at 5200, will the MX keep on going to that level? It seems like I would be wasting my money if it kept shifting at 4200.

Right now I have a 3.00 rear end and am planning on putting in a 3.50, if that makes a difference. My stall is around 2200 rpm.

puttster

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Joined: November 18th, 2004, 4:20 am

February 15th, 2012, 12:09 pm #2

It wouldn't matter if you put a jet engine capable of 50,000 rpm's in front of the transmission.

It will shift when the valves say so.

The 59 Cruisomatic is not the best transmission to start with.
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***no login***
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February 15th, 2012, 2:08 pm #3

To get the most out of a high-winding engine I need a transmission with a modulator? Is that what gives it the flexibility to shift higher rpms?
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Joined: November 18th, 2004, 4:20 am

February 15th, 2012, 3:44 pm #4

What you need is a transmission with more after market options.


Lighter governor, different spring tensions in the valve body, shift kits.

There isn't much available for a 1959 transmission.
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February 15th, 2012, 9:21 pm #5

So when folks (or maybe me) get stock C-6 it probably shifts at 4200 like the MX, but the advantage is the availability of parts. If you put in a bigger engine you can find the C-6 parts to get it to shift at 5000, if desired?

Puttster
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Joined: November 18th, 2004, 4:20 am

February 16th, 2012, 12:02 pm #6

Yes a C6 has more readily available parts.
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truck.doctor
truck.doctor

February 18th, 2012, 1:32 am #7

So when folks (or maybe me) get stock C-6 it probably shifts at 4200 like the MX, but the advantage is the availability of parts. If you put in a bigger engine you can find the C-6 parts to get it to shift at 5000, if desired?

Puttster
was using a fmx auto shift was able to tweek it to shift at 6600-6700 rpms (5000 rpms are for the boe-tie croud). now curently using a c4 with a manual vb i shift it at 7200 rpms with over 600 hps . you got to let them horses out sometimes. 351w-393 stroker.
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Joined: April 25th, 2006, 1:08 am

February 18th, 2012, 6:32 am #8

Can you tella little more about what's needed? Also, when driving around town are the points at the usual places?
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truck.doctor
truck.doctor

February 18th, 2012, 12:37 pm #9

delayed high rpm shift at street operation. although you can crank the shift points down a tad and maintain streetability.this is done by the modulator. note torque converter stall speed and camshaft efect the shift pionts. as the lower idel vacuum raise the shift point also the converter stall efect the shift feel (fimness) although it shifts hard it will not chip the tires on gear change. converters and shift kit parts are getting rare for this model. the C4 or c6 has more performance parts availble. now the aod and the aode are pecoming more popular.
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Joined: April 25th, 2006, 1:08 am

February 19th, 2012, 10:57 am #10

It wouldn't matter if you put a jet engine capable of 50,000 rpm's in front of the transmission.

It will shift when the valves say so.

The 59 Cruisomatic is not the best transmission to start with.
The tranny is in a 1965 Galaxie. Is it okay to use a rod instead of a TV cable with an MX? Is there a way to check or adjust the rod?
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