cdub42 Posted October 20, 2012 Report Share Posted October 20, 2012 So I was driving home from work yesterday in my 79 620. It kept popping out of fifth gear. The last time It did it and i put it back in..fifth gear wasn't there any more. Thoughts? Looks like I'm in the market for another 5 speed! Quote Link to comment
Dat Lurka Posted October 20, 2012 Report Share Posted October 20, 2012 It probably ran away with my missing fan blade. 1 Quote Link to comment
wayno Posted October 20, 2012 Report Share Posted October 20, 2012 When you put it in 5th does it seem loose/differant, like the shifter moves farther than it used to? Quote Link to comment
cdub42 Posted October 20, 2012 Author Report Share Posted October 20, 2012 It does seem to go farther. Sometimes it won't go in at all. Feels like I'm hitting the spinning gear. If I put it in half way it feels like its kinda catching, but it's not transmitting power. Quote Link to comment
wayno Posted October 20, 2012 Report Share Posted October 20, 2012 I beleave there is a nut on the rear shaft that might have come loose, but I could be wrong. Quote Link to comment
cdub42 Posted October 20, 2012 Author Report Share Posted October 20, 2012 Inside the tranny? What are those things like to take apart Quote Link to comment
datzenmike Posted October 20, 2012 Report Share Posted October 20, 2012 Wa ha ha ha..... Does your speedometer still work? Reverse is OK? Quote Link to comment
ggzilla Posted October 20, 2012 Report Share Posted October 20, 2012 Those homeless guys will take anything not bolted down... Quote Link to comment
I'm BLUE Posted October 20, 2012 Report Share Posted October 20, 2012 I beleave there is a nut on the rear shaft that might have come loose, but I could be wrong. Inside the tranny? What are those things like to take apart Wayno is correct .. this is exactly what I was going to type. 7earlier 280z 5spd's are notorious for this. Big main-shaft nut on the rear works itself loose .... Nissan later reversed the thread pitch .. on the later 5spd's .. to prevent this from happening. pop off tail-housing ... not to bad ... I can't remember exactly as it's been a while since I've had to tighten one and my memory isn't so good these days. 30-something mm shaft nut ? ... can't remember it's been a long time ... might have to make a wrench or dedicate an adjustable one if one can't be found. Someguys spin it back on and tighten with loc-tite Quote Link to comment
cdub42 Posted October 20, 2012 Author Report Share Posted October 20, 2012 That picture makes the idea of taking it all apart not so scary. Quote Link to comment
datzenmike Posted October 21, 2012 Report Share Posted October 21, 2012 Order a rear seal #32136-U0100 only $5 and only seconds to change while the tail is off. Good drip insurance. Grease it before putting the tail back on. This will prevent tearing it or a dry start up. You should be able to do this without draining it.... unless it needs to be changed. Just forward of the shifter is that 'bolt'. remove it and the springs inside and save... This is what causes the shifter to to jump into the 3/4 position when in neutral. You have to pull the shifter towards you to get in the 1/2 shift gate and push away to get the 5th/rev gate. Remove the 10mm bolt and key, and pull the speedometer pinion straight out. Your '79 may have these two switches in the tailstock. Neutral switch just forward of the shifter with two yellow wires on it. The other (top gear switch) is lower down and to the right also with two yellow wires. Just remove and keep so they go back in the same positions. Stand the tranny up on two lengths of 2x4 to keep the nose out of the dirt and remove the case bolts around the adapter plate. Twist the shifter over to the left or driver's side , and tap case upward with a soft hammer. Have someone hold the adapter plate to avoid separating it from the bottom (front) case. You're half way there. . Quote Link to comment
Dat510_Chris Posted October 21, 2012 Report Share Posted October 21, 2012 If you do end up re-tightening that nut be sure not to over do it, My 5 speed ended up welding fifth gear to the spacer and tearing the tiny ball bearing holding the spacer through the main shaft, forgot to get picks of it after it broke but here are some before shots. Quote Link to comment
datzenmike Posted October 21, 2012 Report Share Posted October 21, 2012 I wonder if it would hurt to tack weld it to the mainshaft. Unlikely you would ever have to take off again. Just touch it with an angle grinder to remove. Quote Link to comment
wayno Posted October 21, 2012 Report Share Posted October 21, 2012 That is what the transmission shops are told to do, but my guys didn't like that idea, so they found a second nut and put it on behind the first nut. This was done to my 1968 datsun roadster 5 speed after the rear nut came loose. Quote Link to comment
Stoffregen Motorsports Posted October 21, 2012 Report Share Posted October 21, 2012 I beleave there is a nut on the rear shaft that might have come loose, but I could be wrong. Yeah, there is a nut. It is common for those to back off and sometimes come all the way loose. Then when you shift, you're actually pushing 5th gear away. Quote Link to comment
Stoffregen Motorsports Posted October 21, 2012 Report Share Posted October 21, 2012 I made a extension socket for building those transmissions. I cut a snap-on socket in half and welded a piece of 1.5" tubing in between, then I can hit the nut with my air gun. Always use red loctite on the threads and be sure to check for end play after you've tightened it all up. If the thrust washer is worn a bit, you can accidentially over tighten the nut and loose all your endplay. I've done this too! You end up welding the gears together by friction. You can also hit the thrust washer on a belt sander to make it fresh again. Quote Link to comment
cdub42 Posted October 22, 2012 Author Report Share Posted October 22, 2012 Is it safe to drive in its current condition? Quote Link to comment
datzenmike Posted October 22, 2012 Report Share Posted October 22, 2012 I would say so. The gear can't 'fall off' the mainshaft. It's simply just been pushed maybe 1/2" to the rear and just out of range of the shift fork. Because reverse is on the same fork just ease it in and out of reverse when using it to avoid jostling 5th. Otherwise treat it as a 4 speed.... which is what 5 speeds are really... with an extra gear added. If the nut should back off all the way it's possible that the speedometer may stop working. Quote Link to comment
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