Clifton Posted August 17, 2008 Share Posted August 17, 2008 This is the second one I've broke. The roll pin just breaks off on the top. It is still in the shaft and bottom of the fork. It didn't shear off clean. It was in two pieces but that may be from getting caught in a gear. I don't know if it is a roll pin problem or fork problem. I might drill it out and use a shoulder bolt. Has anyone else sheared a roll pin and/or broke a shift fork? Quote Link to comment Share on other sites More sharing options...
rxsleeper Posted August 18, 2008 Share Posted August 18, 2008 Sortof a common problem when racing. I haven't broke one "yet" but have observed another racer break one. FWIW, I have been told to use bolt stock instead of the roll pin and drill/safety wire the bolt stock. I have one tranny at the shop now waiting on a rebuild. I plan on pinning and safety wire. Quote Link to comment Share on other sites More sharing options...
gregkring Posted August 18, 2008 Share Posted August 18, 2008 we would double pin them using a smaller roll pin inside the larger one, or a nail or dowel pin in a pich. Never broke the fork casting, but we would shear the roll pins. This was in a 240Z with a 4 speed and 250 shot of nitrous. Horsepower wouldn't do it, but aggressive shifting trying to get into the 10's would. Quote Link to comment Share on other sites More sharing options...
260DET Posted August 18, 2008 Share Posted August 18, 2008 Nissan uses double roll pins eg in Z32 gearboxes. Its a standard upgrade for early boxes that did not have doubles. Quote Link to comment Share on other sites More sharing options...
Nigel Posted August 18, 2008 Share Posted August 18, 2008 The 240SX transmission also uses double roll pins... Nigel '73 240ZT Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 18, 2008 Share Posted August 18, 2008 We had this discussion on another forum and Don Potter's solution was to use two solid roll pins from a Ferrari I believe. Later Dennis Hale suggested that the problem can be solved by safety wiring the stock pin, as I guess the theory is that problem usually happens when the pin vibrates halfway out of the shift fork, then shears. I suppose you might see part of the pin hanging out the bottom of the rail if this were the case. I've never seen that happen personally, although I have seen vibrations move the 5th gear rail and so the trans can get stuck in 5th gear and 2nd or 5th and 3rd gear at the same time. This then locks the rear tires instantly. I watched my friend slide sideways past a concrete corner worker's stand at fairly high velocity when this happened in my car. There is another possibility... when I see broken shifters and sheared roll pins, I tend to assume the guy driving is shifting like a gorilla on meth. Putting extreme amounts of force on the lever is not the way to shift faster, and if you need to do that to get into the next gear, there is probably something wrong in the transmission, or you're just being overaggressive with the stick. Quote Link to comment Share on other sites More sharing options...
JIM73240Z Posted August 18, 2008 Share Posted August 18, 2008 looking at his vids, it looks like he is fast but smooth in his shifts. playing in his car on saturday i was running through the gears and there was nothing sticking. i was in the parking lot playing like a little kid. i think it is t5 time. jimbo Quote Link to comment Share on other sites More sharing options...
Clifton Posted August 18, 2008 Author Share Posted August 18, 2008 . Later Dennis Hale suggested that the problem can be solved by safety wiring the stock pin, as I guess the theory is that problem usually happens when the pin vibrates halfway out of the shift fork, then shears. I suppose you might see part of the pin hanging out the bottom of the rail if this were the case. It is sticking out some but not much. I shift quick but not with alot of force. I use atleast twice the force when going through the gears on the on the R154 Toy trans but they use a large bolt. If it is the roll pin breaking that causes the fork to break it's an easy fix. If it's the fork breaking first then the pin, it's not so easy. I just talked to a friend that was a Nissan tech for years. He said he's seen a few aluminum ones break along with the roll pins. He said they changed the design of the roll pin too. He had a box of trans parts he's also going to look for. Until now I have run the early boxes with the steel forks and never broke anything. If I can get a steel fork in there I think my problems will be solved. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 18, 2008 Share Posted August 18, 2008 Looks like Dennis might be right on this one. Tough to say for sure, but it definitely looks like it has vibrated part of the way out. Quote Link to comment Share on other sites More sharing options...
Nigel Posted August 18, 2008 Share Posted August 18, 2008 It is sticking out some but not much. I shift quick but not with alot of force. I use atleast twice the force when going through the gears on the on the R154 Toy trans but they use a large bolt. If it is the roll pin breaking that causes the fork to break it's an easy fix. If it's the fork breaking first then the pin, it's not so easy. I just talked to a friend that was a Nissan tech for years. He said he's seen a few aluminum ones break along with the roll pins. He said they changed the design of the roll pin too. He had a box of trans parts he's also going to look for. Until now I have run the early boxes with the steel forks and never broke anything. If I can get a steel fork in there I think my problems will be solved. You can run the steel forks from the 4 speed. That's what I had in my old '82 ZX 5 speed. All you have to do is drill out the roll pin hole for the larger diameter pin used in the aluminum forks. I also used the steel front cover from the 4 speed as well. I've heard of the aluminum ones breaking (although, that's probably due to something binding in the clutch mechanism). Nigel Quote Link to comment Share on other sites More sharing options...
katman Posted August 19, 2008 Share Posted August 19, 2008 Broke lots of pins with various ITS racers. Tried the double Comp pins (pin inside another pin) and the ZX stock pins (single piece of steel rolled into 2 layers). Safety wire wouldn't do anything. Eventually went with 4m solid bolt stock. End of problem. Time spent shifting is time wasted.... Quote Link to comment Share on other sites More sharing options...
Clifton Posted August 19, 2008 Author Share Posted August 19, 2008 Eventually went with 4m solid bolt stock. End of problem. Time spent shifting is time wasted.... I'm getting a box of 81+ trans parts tomarrow, has aluminum forks though. When you went with the 4mm solid rod, was that with aluminum forks or steel? I can keep looking for a 4spd box for steel forks. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 19, 2008 Share Posted August 19, 2008 I think the early 5 speed up through 79 has steel forks too. I thought you were using a T5... Quote Link to comment Share on other sites More sharing options...
Clifton Posted August 19, 2008 Author Share Posted August 19, 2008 No T5 here. I've heard they aren't much better than the Nissan boxes. I have a pre 79' trans and ran it forever without any problems, other than breaking 5th once. This year I went with the later box for the taller 2nd ,3rd, and 5th gear. I could rob a fork out of it but then I wouldn't have a spare trans. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 19, 2008 Share Posted August 19, 2008 No T5 here. I've heard they aren't much better than the Nissan boxes. I have a pre 79' trans and ran it forever without any problems, other than breaking 5th once. This year I went with the later box for the taller 2nd ,3rd, and 5th gear. I could rob a fork out of it but then I wouldn't have a spare trans. You could swap the aluminum forks that your friend has into the spare... Quote Link to comment Share on other sites More sharing options...
Clifton Posted August 19, 2008 Author Share Posted August 19, 2008 I could but then the spare would be a risky to run. I have a month to find a steel one or try the aluminum fork with a solid pin. Quote Link to comment Share on other sites More sharing options...
katman Posted August 23, 2008 Share Posted August 23, 2008 I'm getting a box of 81+ trans parts tomarrow, has aluminum forks though. When you went with the 4mm solid rod, was that with aluminum forks or steel? I can keep looking for a 4spd box for steel forks. Aluminum forks. Never broke any forks. Did wipe the teeth off of 3rd gear once. Downside of having to use 30 year old tranny's.... Quote Link to comment Share on other sites More sharing options...
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