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280zx 5-speed wont shift


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#1 NC280z

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Posted 02 December 2017 - 05:45 PM

Good evening all,

 

I recently purchased an '81ZX 5-speed to swap into my '75 280z, and found that the transmission will only shift into 1st and 2nd gear. I'm using the ZX shifter, and it's clearly engaging the shifter arm. The shifter won't move over to the positions for 3-4 and 5-reverse and any attempt is met with a huge amount of resistance. Unfortunately I did not find this out until the transmission was swapped into my 280. I've also found that even in neutral the engine and transmission are engaged.

 

I swapped back in the original 4-speed, but I'm curious as to what would cause the 5-speed to not be able to shift and basically always be in-gear. I initially thought it might be a clutch slave cylinder issue, but with the trans out of the car it still won't shift into any position other than 1-2. I've read that it may be a bent shift fork, or that it may have something to do with the striker rod. Anybody have any suggestions/fixes? My only experience with transmissions is doing the basic clutch change. 



#2 datzenmike

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Posted 02 December 2017 - 06:30 PM

 

 

  I've also found that even in neutral the engine and transmission are engaged.

 

 

 

This is interesting.

 

Can you actually start in first and shift into second gear? Can you down shift into first again? Are there two separate gears?

When in neutral what gear does it stay in?


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#3 NC280z

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Posted 03 December 2017 - 04:16 AM

I can only shift between what should be first and second. I have no way of telling what gear it's in while in neutral, but it's definitely stuck somehow and turning the driveshaft while in neutral also turns the engine over. Maybe i should disassemble it and check for stuck gears/forks?

#4 NC280z

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Posted 03 December 2017 - 04:16 AM

I can only shift between what should be first and second. I have no way of telling what gear it's in while in neutral, but it's definitely stuck somehow and turning the driveshaft while in neutral also turns the engine over. Maybe i should disassemble it and check for stuck gears/forks?

#5 Crashtd420

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Posted 03 December 2017 - 06:46 AM

I can only shift between what should be first and second. I have no way of telling what gear it's in while in neutral, but it's definitely stuck somehow and turning the driveshaft while in neutral also turns the engine over. Maybe i should disassemble it and check for stuck gears/forks?


That was gonna be my suggestion... when I bought a trans for my 521 I couldn't get it into 3rd or 4th.....
I opened up the bottom I was able to tap with a rubber mallet the shift forks and whatever they moved and everything worked fine after.
I assume it was just from sitting with no oil in it before I bought it....

#6 datzenmike

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Posted 03 December 2017 - 08:02 AM

My guess is that the rear case was removed but put back together incorrectly. With the transmission vertical, the shift rods must all be in the neutral position and the striker rod has to be turned and held clockwise. This will rotate the inside part away from the ends of the shift rods and (with some blind fumblings ) allow you to slide it into the neutral gate as the case is lowered into position on the adapter plate. It is very easy to bump any of the shift rods forward. The 'finger' should enter the 5th/reverse shift rod and slide across the neutral gate as the case mates.

 

aSXgN83.jpg

 

This is the internal end of the striker rod viewed from the front looking to the rear. With the shifter end turned clockwise that 'finger' pointing down to the left will rotate to the right out of the way.

 

e56Vc7b.jpg

 

Shift fork ends on right. Top is 1/2 then 3/4 and bottom is 5/R

 

 

Here they are with 1/2 and 3/4 in alignment, 5/R is not. It's in 5th gear.

 

LPi9nut.jpg


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#7 Stoffregen Motorsports

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Posted 03 December 2017 - 08:27 AM

Sometimes they overshift (discussion about limiting stops). If this happens, you can really hurt things by forcing it out of gear.

 

I would guess that Mike's suggestion of a problem in the tailhousing is correct. If you're pulling the cases, look for signs of overshifting too. Usually it can be spotted by looking at the detent pawls in the shift hub. If they're sticking out at awkward angles, then you likely found the problem.



#8 docbainey

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Posted 03 December 2017 - 09:36 AM

Wouldn't be surprised if you'll find a broken roll pin or two also. Very least the tail housing has to come off.



#9 DanielC

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Posted 03 December 2017 - 11:56 AM

Those are great pictures for explaining what is going on inside a transmission when shifted.

 

There are also two detent balls that fit into notches in the shifting rods in the transmission.  These detents prevent  two adjacent shift rods from both moving.  However, is is possible  to move the 1-2 shift rod, and the 5-R shift rod if the 3-4 shift rod stays in neutral.  This puts the transmission into two different gears at once. 



#10 NC280z

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Posted 03 December 2017 - 12:13 PM

Thanks for the photos and advice! I'm going to pull the tailhousing either tonight or next weekend and see what's going on

#11 datzenmike

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Posted 03 December 2017 - 01:43 PM

Make a stand from two pieces of 2x4 laying flat on the ground. Probably ok but just in case remove the speedometer sleeve. The reverse check sleeve on the left side you can leave. In advance get a new $4 rear seal and replace it while the case is off.

 

 

Is there any evidence that the transmission has been apart? like red or blue RTV used for sealer?


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#12 NC280z

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Posted 03 December 2017 - 04:11 PM

I've got an old wooden pallet and a plastic tub to use for storage as I disassemble it. There's no evidence that it's been taken apart before, so I'm not sure what could've happened. The seller says it shifted fine when he took it out of the donor car, but I didn't think to check how well it shifted when it came in through FedEx. I've got a new rear seal in the trans, but I'll need to pick up a gasket for the tailhousing. 



#13 datzenmike

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Posted 03 December 2017 - 04:27 PM

 

 and found that the transmission will only shift into 1st and 2nd gear. I'm using the ZX shifter, and it's clearly engaging the shifter arm. The shifter won't move over to the positions for 3-4 and 5-reverse and any attempt is met with a huge amount of resistance.

 

 

I have to ask does the shifter move forward into first and travel back about 5" for second???

 

Was it shipped with the shifter installed????


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#14 NC280z

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Posted 03 December 2017 - 06:04 PM

So it looks like the 5-R shift rod was slightly engaged, which is why I could only shift 1-2, and could not move the shifter to the 5-R position. I've put the tailhousing back on and can shift through all gears, now I just need to figure out how to seal it.

 

I'm thinking that maybe the 5-R shift rod was gummed up and prevented it to returning to the fully neutral position? Or maybe it got rocked out-of-place during shipping. Datzenmike, those photos you posted were a lifesaver! If you find yourself in the D.C. area of Virginia I owe you some beers!



#15 datzenmike

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Posted 04 December 2017 - 07:53 AM

Glad to help.

 

Permatex sealant. Make sure it says sealant not that RTV stuff. I used a gray color. Use sparingly as it squeezes out inside too. Let set for 10? min and join. I swapped a diesel tail onto my 5 speed took 3 tries so... If you have it together you can try prying apart just enough to rub some into the crack.


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#16 NC280z

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Posted 10 December 2017 - 10:41 AM

In the rush to diagnose my transmission's shifting issues, I pulled a plug and forgot to index it's original position. Should the curve be facing toward the engine, or toward the diff on this thing? Also, what the hell is it?

 

https://imgur.com/91xKIO6



#17 datzenmike

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Posted 10 December 2017 - 10:51 AM

91xKIO6.jpg

 

This is the reverse check sleeve and fits into the hole on the left in the picture below...

 

aSXgN83.jpg

 

See that short stubby 'finger' sticking down to the left? The check sleeve prevents the striking rod from moving forward into reverse when shifting out of 5th gear. It will allow the striking rod to move sideways and then forward into reverse. It's like a little gate half open that you have to walk around to get through. It's to prevent downshifting into reverse.

 

 

 

1..3..5

---N---

2..4..R

 

 

 

I would say that the left side faced the rear and the right faces the front. Easy enough to check when in. Put into 5th and try pulling straight back into reverse. It should stop you at the neutral gate. Shift sideways to the left and then go full right and you should be able to select reverse.


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