550 Transmission Issue

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Niobrara Charlie
MC crawler
MC crawler
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Joined: Sun Feb 19, 2012 12:59 pm
Location: Nebraska Panhandle Ranch

550 Transmission Issue

Post by Niobrara Charlie » Fri Mar 02, 2012 10:49 am

As a Newby to crawlers, am looking at a '78 550. Field Testing revealed a slight hesitation when engaging into Reverse, from all three Ranges. Rev clutch seems to hook up OK, after the 1-2 second delay. Very recent history on the machine showed documentation of $12.5k of drive-line work, including transmission, performed by JD Shop, (less than 100 hrs ago).
Just completed pressure testing with gauge at selector valve with following results: (Fwd & Rev included First & Second ranges)
Port #5, main pressure N=75psi Fwd=225psi Rev=225psi
Port #6, Rev Clutch Pack N=30psi Fwd=65psi Rev=210psi
Port #7, Fwd Clutch Pack N=30psi Fwd=200psi Rev=100psi

Any thoughts??? Maybe should increase pressures at
Main relief valve and Rate of Shift relief valve???
Ford 9N, JD 720G, JD 410B BH, Farmall Super M, IHC 986, CAT E120B Track Exc.

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digitup2
350 crawler
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Post by digitup2 » Fri Mar 02, 2012 11:41 am

You have a directional pack [forward-reverse] on a shaft .then you have a [1-2 gear] set on single shaft then a [3rd]by it's self on a single shaft .So here it is forward and reverse should test the same two pressures in all ranges if they don't then pressure differences will be in the range packs .So test 1F-1R then 2F-2R then 3F-3R.If the directional pressures are different and don't correspond across all 3 ranges then the problem is in the range shift not the directional.Digitup.

Niobrara Charlie
MC crawler
MC crawler
Posts: 2
Joined: Sun Feb 19, 2012 12:59 pm
Location: Nebraska Panhandle Ranch

Post by Niobrara Charlie » Fri Mar 02, 2012 12:53 pm

Thanks for the quick reply Digitup...

Clarification of pressure test results:

Port #5, Main N=75psi 1&2F=225psi 1&2R=225psi
Port #6, Rev Pack N=30psi 1&2F=65psi 1&2R=210psi
Port #7, Fwd Pack N=30psi 1&2F=200psi 1&2R=100psi

Guess I should check above ports at 3F and 3R.

Also Ports #8, 9 & 10 (1st, 2nd & 3rd Packs at N, 123F & 123R)???

So far it seems that final presure builds at same rate in Rev pack as in Fwd pack.
Ford 9N, JD 720G, JD 410B BH, Farmall Super M, IHC 986, CAT E120B Track Exc.

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digitup2
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Post by digitup2 » Fri Mar 02, 2012 8:32 pm

The story isn't only told by the pressure while in the gears but also pressure fluctuation between gears tells of seals and other problems .It may seem strange to some but the seal on the clutch pack piston will usually be the main pain on a John Deere power shift as the piston is aluminum and the seal tends to wear a grove in the slide area .And the o ring seal will even roll at a certain point showing good pressure again .I think this is the best way to say it without getting too technical.But as the grove is wore the seal will make the pressure change from one time to an other even in the same gear depending on the condition of the o ring and where it sits .Digitup.

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