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Mattman 
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Joined: 20 Dec 2012
Location: Plover, WI
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 Topic: 7040 torque limiter question
Posted: 16 Oct 2024 at 2:31pm |
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Can I replace a 7040 powershift 4 pad torque limiter with a 6 pad 12"? Is there any modifications necessary? I am looking to get more bite. I also plan on doing the extra washers. Any help is appreciated.
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DrAllis
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Posted: 16 Oct 2024 at 3:44pm |
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You can, but six pads (of the same size) will slip easier than 4 pads. From the school of hard knocks back in 1975.
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Lynn Marshall
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Posted: 16 Oct 2024 at 6:30pm |
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You can, but it shouldn't be necessary. If you're adding a second Bellville spring, slipping won't be a problem. I've done a couple of tractors where I had the machine shop mill the surfaces a little bit under the spec so that it made things tighter.
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Mattman
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Posted: 17 Oct 2024 at 7:46am |
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Anyone know the agco # for the powershift torque limiter in an 76' 7040?
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Alvin M
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Posted: 17 Oct 2024 at 8:03am |
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70268718V
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Mattman
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Posted: 17 Oct 2024 at 8:05am |
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Thank you!
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ekjdm14
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Posted: 17 Oct 2024 at 9:13am |
 DrAllis wrote:
You can, but six pads (of the same size) will slip easier than 4 pads. From the school of hard knocks back in 1975. |
This ^
More pads = bigger surface area = less overall pressure on the pads. This is why high-HP car builds often go with "puck" type clutch discs over a traditional "full" disc, less surface area gives more bite for the same spring pressure hence a clutch that's not overly heavy but grabs a lot better. (and in the case of dry clutches, wears a lot sooner).
Not sure what the reason is for trying to gain bite, but if it's "mission critical" & you don't mind the prospect of reduced maintenance intervals I'd consider looking into having the puck material machined (either grooved or just area reduced). Bearing in mind this comes from purely theoretical thinking & I have no experience of doing this, but seems a sound idea to me. YMMV
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Kevin in WA
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Posted: 17 Oct 2024 at 10:16am |
I know we have been down this road before but for what its worth, yes there is less pressure per pad on a 6 but there is also 6 pads holding vs 4, I have replaced dozens of torque limiters over the years and for me the 6 pad always require less slipping on break in to get them to hold, The heavy duty cummins conversion torque limiter from Hy-Capacity has 6 pads for a reason.
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DrAllis
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Posted: 17 Oct 2024 at 11:02am |
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My premise is 6 pads versus 4 pads of the IDENTICAL size/shape/thickness and also with the exact same pressure plate squeeze.. The OP wants to tractor pull this unit and 3 pads will transmit more torque than 4 before slipping any. 4 pads will transmit more torque than 6. I learned this a looooong time ago with a custom made tractor pulling button clutch. The disc had 6 or 8 pads on each side and that clutch wouldn't even move the sled. Disassembled and removed HALF of the pads and then the clutch worked acceptably. This advice was given to me by a veteran puller who said "more pads ?? you need waay more squeeze to get them to hold". He was right. I was wrong.
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