Dime Dave Posted June 28, 2013 Report Share Posted June 28, 2013 I've been doing my research and I have some questions about the driveshaft modifications when swapping a dogleg 5 speed into a 521 pick-up. Both transmissions are the same length, but the 521 4 speed has a flanged output on the tailshaft. The dogleg 5 speed has a slip yoke. The first u-joint on the 521 driveshaft is the same as the u-joint that fits the slip yoke that goes into the dogleg 5 speed. If you were to swap the flange connection for a slip yoke at the 1st u-joint of the 521 driveshaft would the driveshaft work? The only issue I could imagine is the slip joint in the middle of the 521 drive shaft might move, shortening the effective driveshaft length and pull the slip yoke to far out of the transmission for proper engagement. I would suppose a sleeve could be installed over the slip joint in the 521 driveshaft, which would keep it from shortening. What have other folks done to get the driveshaft to work when converting from a drive flange to slip yoke connection at the transmission? Quote Link to comment
erichwaslike Posted June 28, 2013 Report Share Posted June 28, 2013 yes you can i have the setup in my truck... just swap flanges.....and mines a 521 also Quote Link to comment
Jayden71 Posted June 29, 2013 Report Share Posted June 29, 2013 When my front ujoint blew up and took out the back of my stock 4spd with it, that flange piece slid right off the output shaft. SOooooo....when I put the dogleg in, I slid that flange piece onto dogleg output shaft and bolted my flanged driveline up. Works like a charm. No leaks or nothin Quote Link to comment
datzenmike Posted June 29, 2013 Report Share Posted June 29, 2013 Take the 521 4 speed out by unbolting the flange from the driveshaft. In the center of the transmission half of the flange is a large nut. Remove it and the flange will slide back and off the transmission The nut holds the flange and spline to the output of the transmission.... Here's the same 521 4 speed with the flange removed and the nut spun on for safe keeping... Here is a dogleg 5 speed with the flange output installed. Note that because there is no nut or way to use a nut on this transmission there is an uncovered hole that needs to be plugged or oil will seep out past the spline. To fix this get a 40mm frost or core plug for an engine block or the equivalent. Put a little sealer on it to be sure. Install and bolt it up. . Quote Link to comment
Phixius Posted June 29, 2013 Report Share Posted June 29, 2013 You can also use a 520 driveshaft as a one peice upgrade after you put the flange on... Quote Link to comment
skyblue Posted July 1, 2013 Report Share Posted July 1, 2013 I have what datzenmike just explained with the plug as well as a one-piece from a 520 as phixius stated. works great. no oil leaking from flange and no carrier bearing to deal with. small note, if you do go with the 520 one-piece get it balanced before you install it, unless you know for sure its fine. I got mine from a PnP and it needed balancing. Quote Link to comment
Dime Dave Posted July 1, 2013 Author Report Share Posted July 1, 2013 Regarding a 520 single piece driveshaft, is is the same diameter as the 2 piece? (and 520's are like finding hen's teeth 'round my parts).The 510 Wagon drive shaft uses the same u-joints as as the 2 piece 521, but with the 510 wagon they increased the shaft's tube diameter just right up to just before the U-joint ends. The bigger shaft diameter allows for more RPM before hitting the shaft's design limit. The 2 peice shaft, even with a smaller diameter, will run higher RPM's because the driveshaft tube lengths are shorter.Critical speed on a drivbeshaft is determined by tube diameter and length of tube. Go to a longer length and/or smaller diameter and the RPM limt goes down, bigger diameter and/or shorter length, the RPM limit goes up.The driveshaft in my Datsun 1200 racecar at redline in 5th is turning around 10K. That is something you do not want coming appart.Here is a picture posted by CarterB showing the stock wagon d-shaft (bottom) compared to other 510 shafts. Quote Link to comment
erichwaslike Posted July 9, 2013 Report Share Posted July 9, 2013 are you going to be spining your 521 at that rpm... if not, dont worry about it..... and if you are id chose something besides a dogleg..... Quote Link to comment
Dime Dave Posted July 10, 2013 Author Report Share Posted July 10, 2013 No plans to run the 521 engine over or anywhere near 8K. I was just using my 1200 racecar as an example of how in some applications the drive shaft can get to ludicrous speed. Quote Link to comment
datzenmike Posted July 10, 2013 Report Share Posted July 10, 2013 The driveshaft in my Datsun 1200 racecar at redline in 5th is turning around 10K. That is something you do not want coming appart. . On a one to one 5th gear the engine would be at 10K!!!. If you have an overdrive 5th a bit less maybe 12 -15% Quote Link to comment
Dime Dave Posted July 10, 2013 Author Report Share Posted July 10, 2013 Mike, Overdrive turns the output faster than the input or it "overdrives" the output shaft so you are correct the engine is less than the 10K shaft speed. The .854 OD in my 63 series dogleg at 8300RPM (the redline for my A15 race engine) turns the driveshaft at 9718.97 RPM (8300/.854) Quote Link to comment
datzenmike Posted July 10, 2013 Report Share Posted July 10, 2013 That's a lot of spinning energy. Within a foot of your ass... Quote Link to comment
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