Datsun 510 Stuck in Reverse

[jcd0402]

So, yeah, like the title says, my transnission (oem 4 speed) won't come out of reverse. I've tried everything, I've pushed the lever into reverse, I've pulled hard and smaked the release arm, I've even moved the car while it being in reverde to see if maybe the rotationg of the engine would release the gear. 

*Quick info

The gear selector goes into first and second gear yet 3rd, 4th and reverse don't engage. This all happens while the transmission gear is still in reverse but the shifter isn't. 

Meaning, the shifter can be in neutral but the transmission is still stuck in reverse. 

 

Thank you

[datzenmike]

If you shift into 1st or 2nd and let the clutch out what happens? If it stalls then the rev shift fork might be broken and it's permanently in reverse.  If it backs up then striking rod is not selecting 1st or 2nd even though the lever seems to say it is.

 

Hail Mary.... take the dust boot off the shifter and look down in there for something broken or not moving

 

.

If nothing then the problem is internal. One way or another the transmission has to come out. Might be a good time to move up to a 5 speed from a 620 truck, 280z, 280zx 810 or Maxima.

[jcd0402]

1 hour ago, datzenmike said:

If you shift into 1st or 2nd and let the clutch out what happens? If it stalls then the rev shift fork might be broken and it's permanently in reverse.  If it backs up then striking rod is not selecting 1st or 2nd even though the lever seems to say it is.

 

Hail Mary.... take the dust boot off the shifter and look down in there for something broken or not moving

 

.

If nothing then the problem is internal. One way or another the transmission has to come out. Might be a good time to move up to a 5 speed from a 620 truck, 280z, 280zx 810 or Maxima.

When I disengage the clutch the car doesn't move. Yet, when I move the gear lever the second shaft, the one with the pin and lock in your pic moves forward and backwards. Also, I'm not turning the engine on I'm using the starter right now to rotate the transmission which does hesistate when I move it into first and second gear and the car won't move. But, when I do place it into neutral the car launches bakwards. 

 

Also, I already spent too much money on the transmission clutch and pilot bearing and flywheel resurfacing and throwout bearing to toss it out for a 5 speed specially after having a new driveshaft made for this transmission. 

 

Sorry, I know I may sound confusing. 

 

One last thing, I do happen to have another 4 speed transmission laying around but its from a datsun 1600 which has a different bellhousing. Yet, I believe everyting else is the same parts wise except gear ratio wise. Could this be my salvation?

 

[datzenmike]

OK to be clear... if in neutral it tries to back up. If in 1st or 2nd it does nothing.

 

It's jammed in reverse. Good news is you can remove the bottom cover plate (or oil pan) from the transmission and get a good look in there. With luck the shifter just jumped out of reverse without moving the shift rod with it. You can place the shifter in neutral and manually push the reverse shift rod back into the neutral position. This will fix it, HOWEVER....

 

 If the reverse shift rod is in the proper neutral position it may be the roll pin on the reverse shift fork has sheared off and the shift rod is now not moving the fork. The reverse shift rod is on the drivers side of the transmission and the reverse shift fork the one closest to the back of the transmission and is smaller looking that the other two. I'm not sure if the pin can be gotten at to remove and replace if it is broken.

[Stoffregen Motorsports]

It is very common for the nut on the tailshaft to come loose. When it does, it can cause all sorts of problems. It can only be accessed by removing the tailshaft housing.

 

I think I've mentioned how I "set the stops" on Datsun transmissions. Doing this keeps them from overshifting and getting stuck in a gear. Not so important on a road car trans (unless the factory set stops are worn out from years of abuse). It was something I did on all racing transmissions, and they at least got checked when building a street trans.

[jcd0402]

6 hours ago, datzenmike said:

OK to be clear... if in neutral it tries to back up. If in 1st or 2nd it does nothing.

 

It's jammed in reverse. Good news is you can remove the bottom cover plate (or oil pan) from the transmission and get a good look in there. With luck the shifter just jumped out of reverse without moving the shift rod with it. You can place the shifter in neutral and manually push the reverse shift rod back into the neutral position. This will fix it, HOWEVER....

 

 If the reverse shift rod is in the proper neutral position it may be the roll pin on the reverse shift fork has sheared off and the shift rod is now not moving the fork. The reverse shift rod is on the drivers side of the transmission and the reverse shift fork the one closest to the back of the transmission and is smaller looking that the other two. I'm not sure if the pin can be gotten at to remove and replace if it is broken.

Yup, it does exactly as you said in your first comment. In neutral it backs up but in 1st and 2nd it does nothing. 

Edited August 12, 2018 by jcd0402

[datzenmike]

The early 71B had this problem. Later ones had a special nut that had a shoulder on it that could be staked into a groove on the mainshaft. Usually a loose nut caused a loss of reverse (or 5th if a 5 speed)

 

 

I see now that the reverse gear and fork are in the tailshaft and not visible... but the reverse shift rod is. The roll pin securing the fork to the reverse rod may have sheared. Have someone place into and out or reverse while you watch. If the rod moves then the fork is not.

 

If the rod does not move, place in neutral and push the rod to the rear. This might reset it.

 

[jcd0402]

The shifter won't let me go into 3rd, 4th or reverse. Its like they don't exist in the gear selector. 

[datzenmike]

Well again take the bottom cover plate off and see what's moving and what's not. The top most rod is the 1/2 shift. It would seem that is working. It can't be in two gears at once so if in reverse it can't be going into 3/4 so 3/4 should be in the neutral position.

 

Just to be clear it moves forward and back into 1st and 2nd. It does not move to the right through the neutral gate to 3/4 or farther to reverse???

[jcd0402]

1 hour ago, datzenmike said:

Just to be clear it moves forward and back into 1st and 2nd. It does not move to the right through the neutral gate to 3/4 or farther to reverse???

Yup, and it doesn't move further right through the neutral gate. 

[datzenmike]

Weird combination. Was it hard to get out of reverse when this happened?

 

 

I had the same transmission in my '71 521 and it stuck in 4th. No amount of work could get it free. I replaced it.

[Stoffregen Motorsports]

The stock roll pins are notorious for shearing off. I replace them with a "dual roll pin" that you can get from McMaster Carr.

 

Here's a thread just about roll pins:

 

 

[jcd0402]

5 hours ago, datzenmike said:

Weird combination. Was it hard to get out of reverse when this happened?

 

 

I had the same transmission in my '71 521 and it stuck in 4th. No amount of work could get it free. I replaced it.

I never got it out of reverse, I guess I got it like that from the previous owner. Yeah, I even used my feet to push it further right and nothing. I might just swap the bell housing from the roadster transmission and the 510 transmission to fix it if its badly messed up. 

[jcd0402]

1 hour ago, Stoffregen Motorsports said:

The stock roll pins are notorious for shearing off. I replace them with a "dual roll pin" that you can get from McMaster Carr.

 

Here's a thread just about roll pins:

 

 

Thank you, I'll take a look at it today, I don't know much about transmission but the online diagrams help out a lot. Also the youtube videos that I've managed to find. 

[datzenmike]

5 hours ago, jcd0402 said:

I never got it out of reverse, I guess I got it like that from the previous owner. Yeah, I even used my feet to push it further right and nothing. I might just swap the bell housing from the roadster transmission and the 510 transmission to fix it if its badly messed up. 

 

The shift forks, reverse gear and the shift rod gates are in the rear case. If anything is messed up it will most likely be here.

[jcd0402]

I'll go ahead and disassemble it tomorrow, really sucks having to un mount the trany and driveshaft again. ? I'll keep you updated. 

[Stoffregen Motorsports]

Yeah, it sucks, but this has got to be one of the easiest cars to work on. I once replaced my clutch in my 510 race car in under 30 minutes, by myself.

 

If you can't find the problem, post lots of pics. Someone will be sure to spot the problem from a good pic.

[jcd0402]

I'll make sure to post a pic once I'm done uninstalling it. Had to leave town for work, will be back by friday hopefully. 

[jcd0402]

So yeah, i got the tailshaft apart and found 3 pins just laying there. Where could they be comming from? Linkages seem to be moving without any problems. 

 

https://imgur.com/a/0PJ3KfP

Edited October 6, 2018 by jcd0402

[jcd0402]

[datzenmike]

WTF????? is that beef gravy???? I hope it's just a bad blurry picture. How much oil was in the transmission?

 

 

The screw driver like slot, middle bottom of this picture, is the end of the reverse shift rod. The shift fork is attached to it and moves the reverse gear forward to engage and back to dis-engage. Looks like the reverse fork is forward.

 

Can you clean this off with brake fluid and take some more pictures???

[jcd0402]

Yeah it was forward, somehow the main shaft was seized and I tapped it with a hammer and wuala off it moved and now it shifts perfectly fine. Been moving the gears 20 plus times and they shift perfectly fine now,  reverse also works and all the forks for all the gears move. 

 

Edited October 6, 2018 by jcd0402

[datzenmike]

Again, what does the oil look like? From here it doesn't look too good. Maybe water contaminated.

 

Take the pan off the bottom and rinse it and the main gears with brake fluid.

 

 

2 hours ago, jcd0402 said:

So yeah, i got the tailshaft apart and found 3 pins just laying there. Where could they be comming from? Linkages seem to be moving without any problems. 

 

 

 

This still needs to be addressed. The reverse idler gear that drives the reverse gear, spins on needle bearings. The shift fork for reverse is held onto the shift rod with a roll pin. Reverse has a mechanism that holds it in place from jumping out of gear using a pin, a spring and a check ball. The striking rod above the fork that's in the tail you removed is held on with a roll pin. It looks like a finger sticking down and moves with the shifter. Might be a good idea to check they are in.

 

A roll pin looks lie this.

 

A needle bearing like this.

[jcd0402]

Yup, they look like pins from the bearings. The roll pin from the reverse fork was installed I did check that one. Also the springs that held the shafts from the gear selectors too. Those work fine after cleaning them up, the reverse fork is held in neutral position now. If i were to run the transmission without the bearing pins would something go bad even if I never run into reverse?  Just want to move it home. 10mile drive ??

Edited October 7, 2018 by jcd0402

[datzenmike]

Oh  yes that's a better picture. Doesn't look bad now.

 

When the oil pan was removed was there any metal 'parts' in the bottom?

 

 Well the reverse idler is turning any time the car is moving but not under any load because reverse is not engaged. If the needle bearings are from that I don't see any problem.

 

Grab the mainshaft and wiggle it around. It should turn but not move side to side. There are needle bearings in front of the reverse gear where the mainshaft is supported by the transmission case. In the picture above, the counter shaft (has the 4 gears on it) give it a tug and see if any looseness. It should only rotate like the mainshaft.

 

10 miles should be ok. Fill it with 80w90 gear oil. I use 2 feet of garden hose and a dollar store kitchen funnel. Slide it down from the engine compartment and into the fill hole on the side. When it spills out it's full. Holds 2 liters.