I've got a decision to make

Engine, Transmission and related drivetrain.
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loungin112
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Joined: 05 Mar 2014 21:34
Location: Colorado

I've got a decision to make

Post by loungin112 »

Hey there Realm.

I've got to make a decision about my transmission. Currently, I've got a dogleg 5 speed in my 510 that is hooked up to my L20b.

I think I need to replace the throw out bearing. Symptoms: I've got a slight shimmy when engaging the clutch with light rpm. Also, pretty good leak going on from the bellhousing.

What I've got: In the garage, I've got a 5 speed from an NA 280zx and a 5-speed from a 93 240sx. The condition of the 240sx is unknown. The NA 280zx was used in racing so the syncros are in rough shape.

The quotes I've received here in CO to get the dogleg fixed is ~$900.
The quote I've received to rebuild the 240sx is $1100.

To install the 240sx I would use the bellhousing from the 280zx, modified by Ermish racing, for about $300. Plus a shortened drive shaft for maybe $300 (?) Total: $1700 Or, should I try to rebuild the 240sx myself, saving about $900 or so? (I have never rebuilt a transmission before, so....)
I could get the dogleg fixed
I could install the 280zx and live with the bad synchros.

Using the 240sx would be ideal, but also the most costly option, and I'm really on a tight budget. Plus, I'm trying to avoid downtime during the summer.

Suggestions and discussion is appreciated.
datzenmike
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Re: I've got a decision to make

Post by datzenmike »

Release bearing won't cause shimmy on engagement. Most likely the clutch disc and/or pressure plate.

Leak could be from rear engine seal or the transmission front seal. Check the transmission oil level regularly. If not going down then has to be engine oil. Have to take the transmission out to fix either.

Forget the dogleg. The 71C from the S13 is the better choice. It's much stronger so won't have as much wear as you might think and has better ratios than the zx. Any reasonably competent local machine shop can modify the zx front case. It may be cheaper and you can avoid shipping it.

Image

Just run a 16mm drill through the hole for the 1st/2nd shift rod. Either remove the 62mm counter bearing and put a new 56mm from a zx transmission on it, OR bore the zx counter bearing hole to 62mm. The case has to be thinned in the area shown anyway, so bore it out to 62mm. This is because the 71C gears are wider and the case will tighten and jam on them.

Should look like this when done...

Image
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs
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icehouse
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Joined: 17 Jul 2005 17:06
Location: Everett Wa

Re: I've got a decision to make

Post by icehouse »

datzenmike wrote: 30 Apr 2022 10:00 Release bearing won't cause shimmy on engagement. Most likely the clutch disc and/or pressure plate.

Leak could be from rear engine seal or the transmission front seal. Check the transmission oil level regularly. If not going down then has to be engine oil. Have to take the transmission out to fix either.

Forget the dogleg. The 71C from the S13 is the better choice. It's much stronger so won't have as much wear as you might think and has better ratios than the zx. Any reasonably competent local machine shop can modify the zx front case. It may be cheaper and you can avoid shipping it.

Image

Just run a 16mm drill through the hole for the 1st/2nd shift rod. Either remove the 62mm counter bearing and put a new 56mm from a zx transmission on it, OR bore the zx counter bearing hole to 62mm. The case has to be thinned in the area shown anyway, so bore it out to 62mm. This is because the 71C gears are wider and the case will tighten and jam on them.

Should look like this when done...

Image

Mike couldn't a guy use the B bearing on the counter shaft to avoid machining? My buddy Tegan did that then he just dewalt drilled the shift fork holes bigger. I mean a mill would be a better option but it worked.
"People don't like it when shit doesn't match their rule of thumb." Sam
datzenmike
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Re: I've got a decision to make

Post by datzenmike »

It's mentioned in the text between the two pictures.

If it's being milled thinner anyway and mounted in the jig, might as well go out to 62mm for the improved bearing.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs
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icehouse
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Re: I've got a decision to make

Post by icehouse »

Aww. That the route I always go. Easy and cheap route.
"People don't like it when shit doesn't match their rule of thumb." Sam
loungin112
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Joined: 05 Mar 2014 21:34
Location: Colorado

Re: I've got a decision to make

Post by loungin112 »

I'll be making some phone calls again this week to see if I can find a local machine shop. Last time I made the calls, no one would take on such a project.

I'm guessing the clutch kit would be for the KA trans? Starting to research rebuild kits for the KA trans. Any supplier better than the other?

Aside from the 280zx bell housing, I'm guessing the rest of the unit doesn't have much value?
datzenmike
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Re: I've got a decision to make

Post by datzenmike »

Clutches and transmissions have no relation to each other. They don't care which one you use. If you have an L20B then stab the transmission in and go. Just remember that the current throw out bearing collar is actually part of the clutch assembly and it must stay with the L20B. You could throw a F4W63 4 speed from a 510 on there, or the 71B 4 speed from a z car, the 71B 5 speed, the dogleg from an S10 or even the T5 from a 280zx turbo.... all will work with that L20B clutch and pressure plate. This includes a hybrid 71C as well

As to the clutch on the L20B it's either a 200mm for a car or a 225mm from a truck. The flywheel determines which. Unlikely, but possible, a 240mm flywheel from a 720 Z24 or Z20 engine was put on.
"Nissan 'shit the bed' when they made these, plain and simple." McShagger510 on flattop SUs
loungin112
Posts: 294
Joined: 05 Mar 2014 21:34
Location: Colorado

Re: I've got a decision to make

Post by loungin112 »

Thank you all for your insights, suggestions, and knowledge.

As I progress on a direction, I'll post some updates.

And, please, if there are additional considerations/knowledge, please do provide here on this thread.

Cheers
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