4 speed + 2 speed rear
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Junior User
Joined: Aug 2003
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4 speed + 2 speed rear
Alright guys i have an interesting ? today, here it is! I have a 48 F-6 grain truck w/ a 4 speed non sync. and 2 speed rear. When the truck is not loaded i can start in high and run through gears no prob. Now when i eventually fully load the truck to max gvwr of 15,500 will i be able to start in low, then shift into high and run back through 3rd and and forth to acheive max speed, OR am i stuck with running the truck in low gear when loaded. Max speed in LOW is only about 30-35 mph. Hope u guys can help! TY!
jeff
jeff
Laughing Gas
Joined: Feb 2002
Posts: 932
Likes: 9
From: DFW, TX
I'm not sure how the sync/non-sync plays in this equation, or if it does at all, but you should start in the trans in first gear, diff in low, then shift the diff to high, then shift the trans to 2nd and the difff to low at the same time, then the diff to high, then third and so on. If you've got it loaded to max GVW, you may not be able to run it fast enough to pull the diff into high with the trans in 4th. My dad always called this "split shifting" and insisted that we do it when the truck was loaded, but we could put the diff in high and just use the tranny with the truck empty.
Good Luck!
Good Luck!
Post Fiend
Joined: Sep 2004
Posts: 5,231
Likes: 1
From: Near Fresno, California
I agree, split shifting is the way to go. You might be able to skip a few gears, depending on load and grade. I used the rear end as a passing gear - cruse in high/high, but drop to high and low in the rear when I needed power to pass.
Laughing Gas
Joined: Mar 2005
Posts: 1,109
Likes: 10
From: Thornton, Colorado
The first stick I ever drove was a 5/2 62 CH%^y dumptruck, with a 305. Split shifting is the only way to get it moving with a load. When you opened the hood on that truck you had to look for the engine. I thin I could have rode under the hood without being burned.
Broomfieldbum
Broomfieldbum
Elder User
Joined: Feb 2002
Posts: 910
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From: Maryland
Shifting 2 speed rears can be trickey. They are still using those on trucks made today. If you do not shift it correctly it can mess things up in the rear. When you are going throu the gears lets say you are in 2nd low the engine is wound up and you want to shift into 2nd hi. Shift the 2 speed leaver into hi and let off the gas you should feel it shift. When you are ready for 3rd. This is the hard part, When you shift the trans into 3rd, 3 things need to happen at the same time 1 the shifter going into 3rd gear 2 the 2speed into low 3 as soon as the clutch pedel is 3/4 the way out you need to hit the gas.
If you want to down shift if you are climing a hill lets say your in 4 th gear you can at the same time let off the gas tap the clutch and shift it into low then hit the gas.
Most people start out in low then shift to hi and leave it until they stop. Hope this made sense. I change a lot of rears because the drivers don't understand them.
If you want to down shift if you are climing a hill lets say your in 4 th gear you can at the same time let off the gas tap the clutch and shift it into low then hit the gas.
Most people start out in low then shift to hi and leave it until they stop. Hope this made sense. I change a lot of rears because the drivers don't understand them.
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Junior User
Joined: Aug 2003
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Thanks for the advice everyone! Does anyone know where u can get the 2 speed diaphragm rebuilt? Mine leaks so it will not keep the 2 speed engaged.
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Junior User
Joined: Sep 2005
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Take it apart ant take all the goddies to a power brake shop, or a heavy truck dealer and see if they can help you.I rebuilt one years ago and that is what I did.And I have a 51 F-6 that I am going to have to do it to also.So let me know what you find.
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Junior User
Joined: Sep 2005
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2-Speed
The one that was on the 48 I did you could seperate.I havn't crawled under the one I have now to see if you can seperate it.Check with a local New truck garage and see if any of the old guys there know anything that you could do.In the meantime I will check mine and with a couple of locals I know. I may have the same problem you have.
Senior User
Joined: Aug 2005
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This is going back a few years and I hope you can find the parts needed. I was just told the other day that frame mounted boosters - replacements - will be discontinued in 2006 by one of the large suppliers. This post also reminded me of an old compressor truck that my employer had years ago - a KB 8 International that still had the hand lever for the 2 speed rear end. Good luck with your parts search.
