Weak return to center spring

[Mikes Z car]

Does anyone remember reassembling a 4 or 5 spd transmission from a Z from the 4 spd era to the 5 spd 280ZX transmission era and remember the ease of putting in the return to center bolt? I am wondering if I can pull that bolt out and put it back in without taking the transmission out of the car. My return to center is weak so I tap reverse sometimes when pulling out of 5th. This also makes it hard to find 3rd sometimes. I understand from the two rear ears on my 5 spd that it is the older 5 spd transmission if that helps. I have read of someone else cleaning and greasing the spring and whatever it pushes on (I don't remember it being a ball bearing) and that fixed their weak return to center.

I THINK I remember on my 4 spd from 30 years ago that the return to center bolt can be pushed in with hand force, so that no mechanical help from a vise etc was necessary.

I am assuming that I have correctly identified the purpose for the bolt in the attached picture.

Thanks,

Mike

[Zed Head]

There's little if any pressure on the spring when the big retaining bolt is started. I've had one out a couple of times. If there's room to slide the parts out without hitting the tunnel, it should be pretty easy. I think there's three parts, the bolt, the spring and the "pin".

Can't remember if there's an orientation but I don't think so. Eyeball it as you're removing to be sure. Interested to see if a new spring or some preload will change things. I didn't like that feature of the older transmissions, it was aggravating.

[Captain Obvious]

My return to center is weak so I tap reverse sometimes when pulling out of 5th.

I'll be watching your progress with this as I frequently clip reverse coming out of 5th. I've been inside trannys in the past and it annoys the crap out of me that I do this when I so much know better. I don't know if a stiffer detent spring would fix it, but if it does help and is that easy to put in, that would be excellent!

I didn't like that feature of the older transmissions, it was aggravating.

Zed Head, What do you mean by "feature"? Do you mean the feature of clipping reverse on your way from fifth to fourth? Or the feature of having an anemic detent?

[Zed Head]

The feature of a weak design leading to both things you mentioned. My old 5 speed would drop in to 5th way too easily. The newer 5 speeds (mid-80 and up) have a "reverse avoidance" gizmo added to the tail-shaft housing and a corresponding piece on the shift rod. Helps knock it over to center when dropping down from 5th.

[EuroDat]

Hi Mike, If you are having problems hitting reverse, the spring in your photo is not the problem. I would look at the "Ball checks" and "Popet springs" in the middle section of the transmission. The two on the side can be removed while in the car. The one on top is not so easy. I have never tried to get them out while its still in the car. Maybe someone has done it and can share their experience?

The springs are POS#9 in the drawing.

The spring you are pointing to is used to centre the gear stick. If you push it left or right it will re-center using this spring. Its easy to remove with the transmission in the car. The bolt is a cap and the spring fits into a cap with a flat tab about 3mm wide, 16mm long. That tab fit in a V section which gives it the centering action.

Chas

Link to Carpartsmanual give a good overview of the springs and such.

http://www.carpartsmanual.com/datsunS30/DatsunZIndex/PowerTrain/TransmissionControl/5Speed/tabid/1718/Default.aspx

Edited June 10, 2013 by EuroDat
Link to Cap Parts Manual

[Zed Head]

I see that I missed the part in the first post about up to the ZX transmission. Thought you had an early 4 or 5 speed. Eurodat covered the gizmo I mentioned, with a picture. Introduced in 1980 I believe.

I usually hate the "there's a reason" comments but in this case I think that there is a reason that the engineers added the device shown in Eurodat's picture. It's called the "reverse check sleeve" in the 1982 FSM.

The only thing that I could find on the early transmissions that might help to avoid reverse on the way down from 5th (what I meant to say in my other post) is called the "reverse check spring" in the 1978 FSM. So, apparently, it's supposed to help.

[Captain Obvious]

Zed Head,

I'm not sure you missed anything... Mike says his five speed has two ears on the rear housing which according to this site (Differential Ratios) means that it is an early five speed from a Z:

I've got two ears on mine as well, so I'm thinking that Mike and I have the same genre.

So does that revelation do anything to the suggestions about what to do about clipping reverse on the way out?

[EuroDat]

Hi Guys,

LeonV ran a thread a month or so ago about the differences in the 5 speeds trannys. Can't find it now on my phone. It didn't cover the reverse lock out (Gizmo), but there are enough good photos to see which one you have.

The early model doesnt have the reverse lockt out which means the detents play a big roll keeping it out of reverse. If the popet springs pushing these ball checks are weak it will easily slide through to reverse. See POS#9 in the drawing I posted.

I changed my last year and the gear lever feels like new. Pitty the rest of the tranny is crape:disappoin

Chas

[Mikes Z car]

Zed Head, Captain Obvious, EuroDat,

Thanks to all of you for your great observations. It had never occurred to me to look for a popet detent as having a role in returning the shift lever to neutral. My DD has a 5 spd but is not a z car, it has a strong return to center (but I don't know if it has a reverse avoidance kind of sleeve) so if I pull straight out of 5th with a flat hand giving it freedom of movement it pops over to neutral by itself readily, I want that action on my Z. I am studying LeonV's thread on transmission ID, didn't realize there are different ratios for the same transmission model number. May try a new spring or preload the one I have, hopefully find a solution useful for anyone else, may need help identifying what that solution might be when I get further with this. Thanks for the help!

Mike

LeonV transmission ID thread: (Found with advanced search using LeonV username, his posts are listed then, easier search with a desktop)

http://www.classiczcars.com/forums/engine-drivetrain-s30/49070-transmission-id-quiz.html

Gear chart LeonV references:

gearing2

[EuroDat]

My DD has a 5 spd but is not a z car, it has a strong return to center (but I don't know if it has a reverse avoidance kind of sleeve) so if I pull straight out of 5th with a flat hand giving it freedom of movement it pops over to neutral by itself readily, I want that action on my Z.

Now reading this, you may have a problem (weak springs) in both the popet detents and the centering detent. The springs dont cost much. Less than €12.00 you have all four. In the states they are probably cheaper.

The centering detent is easy to replace.

Mine had very little tension when I unscrewed the cap nut. I could easly start it by hand to get it back in. The new spring needed a lot more pressure to get it started.

The popet detents on the selectors are a bit more of a challenge. The two side detents are the "easiest" to remove. Just be carefull not to lose the ball. Its about 6mm in diameter if I remember correctly. The lowest of the twoo side plugs is for the fifth/reverse action. There is a third one On top. This one will be hard to get to with the transmission in the car. You will need a paper clip of such to hook the spring out. Getting it back in will be a PITA considering the space (or lack of it) you have to work in. You could try just changing the bottom one first and see what the difference is.

That and the centering detent should help solve your problem a lot.

While your at it, you can change the gear lever bushings. That helps tighten up the lever and gives you better control.

They are still avaiable a Nissan.

2x 32855-H1010 (Pos#31) €3.41ea

1x 32861-N4200 (Pos#32) €3.67

Chas

[EuroDat]

Just looking through the links and found my photo of the centering detent. If you look in the "Transmission ID thread in post 10 I posted some photos. In the second last photo you can see a container. The centering detent is just visable in the photo.

Chas

[Mikes Z car]

EuroDat,

Thanks for the great detailed information. I see the spring assembly now in your picture. I will order new springs. Hmm, a longer bolt might compress the spring further giving more force on the pin negating the need for more finger force to start pushing a new spring in; don't think I will try that though. If my fingers can't push the new spring in, I might have to lower the transmission tail end so I can push harder on the new spring to get the spring in as you describe, or could make a temporary pry bar of some kind or, (shudder) drill a temporary hole. Will report back what happens.

Bolt,spring and pin: (EuroDat's picture)

Edited June 10, 2013 by Mikes Z car