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Datrot71

620 driveshaft troubles

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Hey everyone, so I am in a bit of a pickle. 

I have a 76" 620 with a 4 speed I assume the transmission is a F4W71B

I recently removed the stock driveshaft and asked someone to help me rebuild it and thought they knew how to do it since I was only use to replacing driveshaft as a whole. This is where things went south... long story short there are dents in the tube that cant be fixed, the front section of the driveshaft flange nut is stripped and doesnt want to loosen, its a mess. It's hard to find a driveshaft and the only one I found is out of a 78" 5 speed. I have read that the 5 speed is shorter. can this be extended ? and is the yoke that goes into the transmission the same in a 4 speed and 5 speed. Any help is appreciated thank you .  P.s. I would prefer not to go to a one piece driveshaft

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Did you guys put the dents in the shaft when you were working on it? Dents in a driveshaft tube are potential failure points and a probable vibration too.

 

4 and 5 speed slip yokes are the same, mostly.

 

Any driveline shop can re-tube a shaft. Usually only $100 or so, if the joints are usable.

 

If the nut is stripped, you may be SOL. Do you have the correct size socket or were you using one that was "close enough?" If you look inside the socket, there is usually a bevel. Cutting the bevel off in a lathe or with a grinder can help as it gives the socket some extra bite on the nut. Worst case scenario, you slit the nut with a plasma cutter and then chisel it off. I've had to do this before and it is a pain, but does work.

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F4W71B and FS5W71B are the same length on the 620. Splines are the same though there may be some minor difference in lengths, but I don't think so. Besides you can swap them.

 

The '74 and the '77  have to be the same wheelbase for the entire drive shaft to swap. The front half of the 2 piece drive shaft will be the same length regardless of the wheelbase so the front will swap.

 

A one piece driveshaft might work if the truck was lowered otherwise it will hit the cross member on suspension travel.... and there is no one piece for the 620.... So forget that.

 

Let this be a lesson to do your own work. Well meaning friends are just that.... well meaning. They should know to NEVER hammer on the drive shaft tube.

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42 minutes ago, Stoffregen Motorsports said:

Did you guys put the dents in the shaft when you were working on it? Dents in a driveshaft tube are potential failure points and a probable vibration too.

 

4 and 5 speed slip yokes are the same, mostly.

 

Any driveline shop can re-tube a shaft. Usually only $100 or so, if the joints are usable.

 

If the nut is stripped, you may be SOL. Do you have the correct size socket or were you using one that was "close enough?" If you look inside the socket, there is usually a bevel. Cutting the bevel off in a lathe or with a grinder can help as it gives the socket some extra bite on the nut. Worst case scenario, you slit the nut with a plasma cutter and then chisel it off. I've had to do this before and it is a pain, but does work.

The rear section of the shaft has not one but two defined dents in it, unfortunately my friend decided to progress without me there and I come back to two flat spots on the shaft from him hammering the u-joints out. Sucks but things happen I suppose and its trash now. 

 

I'm most likely SOL because I used the correct size socket ( 27mm ) but it's the threads that are an issue. The nut started tightening when loosening the flange nut ,maybe because I not only reused it a second time but also used it to press the new carrier bearing in with the flange * cringe*. I'll give you credit and say you are brave using a plasma cutter to cut the flange nut lol . I was thinking of ways to cut it but the chisel and plasma cutting sounds promising if I'm careful enough haha.

I'll admit this was just a snowball of inexperience lol but now I gotta dig myself out and hopefully the "new to me" shaft from ebay will get me back on track. FYI I'm going to a driveline shop this time around to service it.

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52 minutes ago, datzenmike said:

F4W71B and FS5W71B are the same length on the 620. Splines are the same though there may be some minor difference in lengths, but I don't think so. Besides you can swap them.

 

The '74 and the '77  have to be the same wheelbase for the entire drive shaft to swap. The front half of the 2 piece drive shaft will be the same length regardless of the wheelbase so the front will swap.

 

A one piece driveshaft might work if the truck was lowered otherwise it will hit the cross member on suspension travel.... and there is no one piece for the 620.... So forget that.

 

Let this be a lesson to do your own work. Well meaning friends are just that.... well meaning. They should know to NEVER hammer on the drive shaft tube.

Great! I may just swap them then , also depending on the condition of the yoke on the used  drive shaft I ordered.

 

That's what I figured, my 620 is stock height. Everyone on other group just tell me to go one piece without explaining other implications, glad I choose to stay with a two piece shaft

 

I won't be making the same mistake twice, I'm going to a drive line shop  this time around 

 

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It is also possible to drill the nut and chisel it off. Either way (with plasma or drill) you need to be careful of the threads.

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