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Case Tractors Discussion Forum
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70 series powershift

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Ron Sa

06-21-2012 04:45:31




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Does anyone have a picture that can be posted showing the cross section of a 70 series powershift--any 2 wheel drive model? Thanks.




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JHH

06-22-2012 16:30:13




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 Re: 70 series powershift in reply to keithhorton, 06-21-2012 04:45:31  
third party image

Here you are, Ron. Sorry about the split images, they are foldout pages and my scanner isn't big enough to get them all on one scan.

https://picasaweb.google.com/JHH1346/CasePowerShiftHowItWorks?authuser=0&authkey=Gv1sRgCPKLo_Op6cbulgE&feat=directlink

As you can see the power shift is ahead of the 4 speed range transmission.

Enjoy - Jhh
This post was edited by JHH at 03:39:52 06/23/12 2 times.

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JHH

06-21-2012 10:38:43




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 Re: 70 series powershift in reply to John Saeli, 06-21-2012 04:45:31  
On each up shift or down shift in the Case power shift, one cluth releases and one clutch picks up the load. The smoothness of the shift is controlled by a needle valve that controls how fast the clutch that drops the load releases.



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Adirondack case guy

06-21-2012 08:52:04




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 Re: 70 series powershift in reply to Ron Sa, 06-21-2012 04:45:31  
third party image

Ron,
Ihave this cross section. It's not big. This is in a very unique Case sales brosure which has a series of six plastic overlays, that show the innerds of the 70 Series tractors. It was published in 1970. I may pull the staples and scan the entire book for you guys. It's pretty neat.
Loren

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Ron Sa

06-21-2012 10:04:44




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 Re: 70 series powershift in reply to Adirondack case guy, 06-21-2012 08:52:04  
I would be interested in any additional innerds of the powershift that you might have. One 70 series, that I have run for a friend, had one very rought upshift and I could possibly figure out why if I had details of the powershift mechanism. If there are two load pickup clutches actuated on an upshift that usually causes a rough upshift.



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Adirondack case guy

06-21-2012 16:26:34




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 Re: 70 series powershift in reply to Ron Sa, 06-21-2012 10:04:44  
Ron,
As stated there are no two clutch shifts in an RPS34 Tranny, other than when the clutch pedal is depressed and the pack comes to a hault, momentarly. Your friends tractor could have a simple issue (needle valve set wrong, sorry I can't remember if the needle controls flow, or discharge) There are also 3 feed tubes that supply a rotary manifold with 3 steel metal sealing rings, similar to piston rings, that send presurized oil to the clutch pistons, via porting in the center shaft. Newer 70 series tractors had a metal expansion ring that sliped into the nylon piston rings in the clutch packs, sealing them up better. A weak pump or faulty flow divider valve could also cause harsh shifting. I often wondered if a small acumilator teed in after the flow divider valve would make the RPS34 shift precisely.
Loren.

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Ron Sa

06-22-2012 08:12:39




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 Re: 70 series powershift in reply to Adirondack case guy, 06-21-2012 16:26:34  
No two clutch shifts makes me even more curious about the 70 series PS configuration. Would appreciate it if someone would scan a cross section of the RPS34, or its update, out of a service manual and post it.

Typically, powershift tranny clutches operated in pairs or triples in order to provice a specific ratio.

Without seeing a cross section of the RPS34, I would have guessed four clutches working as pairs to provide the three PS ratios of LOW, MEDIUM, AND HIGH.

I was guessing that----Clutches A and B both are engaged to provide LOW but the master clutch picks up the load causing travel forward or reverse. I understand that releasing the master clutch puts the PS in LOW.

For MEDIUM, Clutches A and C both are engaged to provide MEDIUM-- the master and A stays engaged and B drops out and C picks up. This is what I call a single clutch load drop and single clutch load pick up and these tend to be smooth shifts.

My guess was that HIGH is provided by dropping two and picking up two--- A and C drop out and B and D engage. Here, two clucthes drop out and two clutches pick up. As I recall, upshifting into HIGH was the very rough shift on the tractor that I ran. It is tricky to juggle more that two clutches during a shift.

I interept that you are saying that only two clutches are juggled during either of the two shifts up or down--- one drops out and one picks up. I know that a countershaft PS can do this for two consequetive shifts but I thought it takes a complex planetary in order to do the one drop out and one pick up sequence for two shifts in sequence.

Looking forward to better understanding the 70 series PS.

PS My 8830 Ford has an 18 speed countershaft full powershift with 17 upshifts--all computer controlled shifts. For any one ratio, three clutches are engaged.

For 12 of the shifts, one clutch is dropped and one picks up the load--very smooth.

For 4 of the shifts, two clutches are dropped and two pick up--a tad rough.

For one of the shifts, three clutches are dropped and three clutches pick up--very rough even for the computer to handle.

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