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Allison MT643 Cable Modulator Reseal

October 22, 2020, 10:12:10 pm

Info in this link suggest there is a service kit for the Morse Modulator (pn 310820) http://www.sealandpower.com/Industrial%20Catalog/Modulator%20Control%20Cables(2).pdf
Mine weeps just a bit of fluid, has anyone attempted to service these modulators?

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Re: Allison MT643 Cable Modulator Reseal

Reply #1 – October 23, 2020, 10:00:02 am

No. But I adjusted a little more slack into mine hoping  that the trans shifts a little sooner. Sometimes it shifts at 2200 if you lift a bit, and some times it shifts at 2500..

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Re: Allison MT643 Cable Modulator Reseal

Reply #2 – October 23, 2020, 12:49:21 pm

Modulator in 643 was set for a 45,000 fire truck.  Can be readjusted by an Allison dealer

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Re: Allison MT643 Cable Modulator Reseal

Reply #3 – October 24, 2020, 09:40:05 am

I'll probably wait until it's time to service the fluid to mess with this, the weep is very slow and takes a week to make a drip on the driveway. My understanding is that when you remove it from the trans you get a lot fluid coming out that port..

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Re: Allison MT643 Cable Modulator Reseal

Reply #4 – November 13, 2020, 06:05:48 pm

I was able to find a new modulator and cable assy (cable is not the same but I don't really need a new cable) from Findit Parts. Plan is swap in only the new modulator valve and then double check the adjustment measurements. Per the instructions (I scanned and attached them)  you can switch these from push to pull with just a small change under the cover plate.  Mine appears to be working fine, just a little leaky...for $84 shipped this is worth a shot...these things are not easy to find..

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Re: Allison MT643 Cable Modulator Reseal

Reply #5 – November 13, 2020, 06:18:43 pm

Here's the part number info off the original Morse cable. I'm sure these are available somewhere, pretty sure Teleflex bought out Morse..

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