Driveshaft
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Senior User
Joined: Aug 2008
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From: Tuscumbia , Al
Driveshaft
78 F150 460 C-6 LWB one piece driveshaft from factory now that i made a few mods the shaft is warping . Took shaft to shop had it straightened and re balance i was told the shaft was good for 3800 - 4000 RPM didnt run it 3 days now warped again !! 
I would like to be able to turn it up to 5000 - 5500 RPM has anyone converted to 2 piece or {One piece ALUM or Carbon Fiber if so who do you recommend }
Mine seems to warp at shift points @ 4500 RPM
I would like to be able to turn it up to 5000 - 5500 RPM has anyone converted to 2 piece or {One piece ALUM or Carbon Fiber if so who do you recommend } Mine seems to warp at shift points @ 4500 RPM
Post Fiend
Joined: Jul 2006
Posts: 6,948
Likes: 44
Tak it to a different shop. WHy would they make a claim based upon rpm? In low gear, your driveshaft is turning far greater than the rated rpm. I have only heard of such a thing for balance purposes.
You can have an aluminum shaft built, but these are a little on the expensive side. The tube diameter has to be larger to prevent them from vibrating.
You can and probably should change the driveshaft and step up to a shaft with a thicker wall tube.
Where exactly is your shaft failing? Are you bending the tube? This clearly indicates a shaft that is too thin.
Think you need to find a better shop. I suspect this shop making your repairs might need to stick to doing other things. They sound like they may need a little more experience with d-shafts.
You can have an aluminum shaft built, but these are a little on the expensive side. The tube diameter has to be larger to prevent them from vibrating.
You can and probably should change the driveshaft and step up to a shaft with a thicker wall tube.
Where exactly is your shaft failing? Are you bending the tube? This clearly indicates a shaft that is too thin.
Think you need to find a better shop. I suspect this shop making your repairs might need to stick to doing other things. They sound like they may need a little more experience with d-shafts.
Thread Starter
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Senior User
Joined: Aug 2008
Posts: 124
Likes: 0
From: Tuscumbia , Al
Tak it to a different shop. WHy would they make a claim based upon rpm? In low gear, your driveshaft is turning far greater than the rated rpm. I have only heard of such a thing for balance purposes.
You can have an aluminum shaft built, but these are a little on the expensive side. The tube diameter has to be larger to prevent them from vibrating.
You can and probably should change the driveshaft and step up to a shaft with a thicker wall tube.
Where exactly is your shaft failing? Are you bending the tube? This clearly indicates a shaft that is too thin.
Think you need to find a better shop. I suspect this shop making your repairs might need to stick to doing other things. They sound like they may need a little more experience with d-shafts.
You can have an aluminum shaft built, but these are a little on the expensive side. The tube diameter has to be larger to prevent them from vibrating.
You can and probably should change the driveshaft and step up to a shaft with a thicker wall tube.
Where exactly is your shaft failing? Are you bending the tube? This clearly indicates a shaft that is too thin.
Think you need to find a better shop. I suspect this shop making your repairs might need to stick to doing other things. They sound like they may need a little more experience with d-shafts.
In fact it seems that in a C-6 or any tranny that 1st or 2nd is turning slower than the engine RPM but in 3rd gear it is almost 1-1 Ratio give or take 3 - 500 RPM
Post Fiend
Joined: Jul 2006
Posts: 6,948
Likes: 44
How would a C6 be any different than any other auto trans? Regardless of the math, your yokes have to spin at some pretty extreme rpms. The problem is not here, or associated with the rpm. Your problem is related to the tube diameter and wall thickness.
If you are bending shafts, you need a shaft with a thicker walled tube.
U-joints should be your weakest link, not the wall of the shaft. Beef them up and get some thicker walled tubes in there.
If you are bending shafts, you need a shaft with a thicker walled tube.
U-joints should be your weakest link, not the wall of the shaft. Beef them up and get some thicker walled tubes in there.
Laughing Gas
Joined: Dec 2007
Posts: 1,052
Likes: 2
From: Alvarado, TX
How would a C6 be any different than any other auto trans? Regardless of the math, your yokes have to spin at some pretty extreme rpms. The problem is not here, or associated with the rpm. Your problem is related to the tube diameter and wall thickness.
If you are bending shafts, you need a shaft with a thicker walled tube.
U-joints should be your weakest link, not the wall of the shaft. Beef them up and get some thicker walled tubes in there.
If you are bending shafts, you need a shaft with a thicker walled tube.
U-joints should be your weakest link, not the wall of the shaft. Beef them up and get some thicker walled tubes in there.
I'm running decent power, a shift kit and tall rubber all of which put extra strain on the DS and I've never bent one. My '68 Cougar has a wild big block and the stock DS has survived side stepping the clutch countless times. If just driving around town is bending them it's just too weak or the shop is not doing quality work.
Cargo Master
Joined: Jul 2005
Posts: 2,309
Likes: 364
From: Kansas
ignoring any torque converter slippage, etc. the max driveshaft RPM equals the max engine RPM on a non-overdrive transmission (and occurs in top gear). On an overdrive transmission, divide the max engine RPM by the overdrive ratio to get the max driveshaft RPM...
In lower gears, the driveshaft RPM is lower.
The end of this doc has a chart for determining the max driveshaft RPM for diff sizes of tubes/lengths:
http://www2.dana.com/pdf/J3311-1-HVTSS.PDF
In lower gears, the driveshaft RPM is lower.
The end of this doc has a chart for determining the max driveshaft RPM for diff sizes of tubes/lengths:
http://www2.dana.com/pdf/J3311-1-HVTSS.PDF
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