6 Speed manual Trans S-640 Replacing a 4+3 [Forums - C4 Technical]

C4 Technical > 6 Speed manual Trans S-640 Replacing a 4+3	« 1 (2)
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bogus	Re: 6 Speed manual Trans S-640 Replacing a 4+3	#51
Grand Imperial Pooh-Bah San Pedro, CA 20859 Posts Member since: 2005/9/7 0:00	All I know is that machining the LT1 flywheel down works. And the distance is .090, not .080. I doubt, tho, that the difference matters. I always thought it came from ZFDoc.com...
	Posted on: 2008/6/28 20:50
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FATED	Re: 6 Speed manual Trans S-640 Replacing a 4+3	#52
Guru Newb Texas 157 Posts Member since: 2007/12/30 0:00	I've been thinking about this noise thing. I read somewhere that someone swore by 75wt gear oil in an 84 with a ZF swap. I don't think that could stop the noise but I just bought a gallon of 80-140.
	Posted on: 2008/6/29 0:38
	_________________ 1985, Performance Chip, hole in muffler, and other Mods
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CentralCoaster	Re: 6 Speed manual Trans S-640 Replacing a 4+3	#53
Senior Guru San Diego, CA 9454 Posts Member since: 2007/10/28 0:00	I don't think you'll find anyone that would recommend that. Even the rear end just uses 75w90 gear oil (which is about as thick as 5w30 motor oil, which is the weight GM used originally) The thicker 10w60 Castrol some use will be quieter.
	Posted on: 2008/6/29 1:11
	_________________ 1985 Z51, ZF6
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FATED	Re: 6 Speed manual Trans S-640 Replacing a 4+3	#54
Guru Newb Texas 157 Posts Member since: 2007/12/30 0:00	I tried the light weight high shock Red Line. The noise is really incredible. The clutch feels just like the 85 push though.
	Posted on: 2008/6/29 2:03
	_________________ 1985, Performance Chip, hole in muffler, and other Mods
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CentralCoaster	Re: 6 Speed manual Trans S-640 Replacing a 4+3	#55
Senior Guru San Diego, CA 9454 Posts Member since: 2007/10/28 0:00	Its hard to say. Maybe you had different expectations than most. The fix is usually to turn up the radio.
	Posted on: 2008/6/29 8:26
	_________________ 1985 Z51, ZF6
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FATED	Re: 6 Speed manual Trans S-640 Replacing a 4+3	#56
Guru Newb Texas 157 Posts Member since: 2007/12/30 0:00	I have not done the final timing. Maybe that will help. This noise level would require straight pipes and 400 watts of bass to cover. ZFDOC says this can be normal. It shifts easy to 4 th. and reverse is good. Will try 5 & 6 when I get some room.
	Posted on: 2008/6/29 13:05
	_________________ 1985, Performance Chip, hole in muffler, and other Mods
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pappyfreebird	Re: 6 Speed manual Trans S-640 Replacing a 4+3	#57
Senior Guru 1028 Posts Member since: 2007/12/26 0:00	no input ceptin thought id read that yer 4+3 was fine??? ifn so whats left of it fer a buyer to have on a shelf?
	Posted on: 2008/6/29 15:49

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FATED	Re: 6 Speed manual Trans S-640 Replacing a 4+3	#58
Guru Newb Texas 157 Posts Member since: 2007/12/30 0:00	I have already sold it on the big auction site. Left a week ago.
	Posted on: 2008/6/29 17:18
	_________________ 1985, Performance Chip, hole in muffler, and other Mods
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anesthes	Re: 6 Speed manual Trans S-640 Replacing a 4+3	#59
Master Guru Boston, MA 646 Posts Member since: 2008/6/18 18:02	Quote: bogus wrote: All I know is that machining the LT1 flywheel down works. And the distance is .090, not .080. I doubt, tho, that the difference matters. I always thought it came from ZFDoc.com... I spoke with Bill. He sent me a lot of scans of some articles on converting things. The ZR1 pressure plate was the ones in the scan. Either way, he said hes never done either swap and does things with OEM parts. So no reported reasons? -- Joe
	Posted on: 2008/6/30 11:39

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FATED	Re: 6 Speed manual Trans S-640 Replacing a 4+3	#60
Guru Newb Texas 157 Posts Member since: 2007/12/30 0:00	I think that somewhere in this string I said that I had to cut the 3/8 master Cyl. shim to fit up the clutch. I didn't have to. Put the rest of the shim back in and the clutch works fine. Drove it this morning and noticed the clutch engaged a little high. Thought about that and put the shim back in. Also the noise is not that bad if you never let it idle in neutral. After all is done I am going to start pulling it all apart for a rear oil seal leak.
	Posted on: 2008/7/2 18:11
	_________________ 1985, Performance Chip, hole in muffler, and other Mods
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FATED	Re: 6 Speed manual Trans S-640 Replacing a 4+3	#61
Guru Newb Texas 157 Posts Member since: 2007/12/30 0:00	I have reassembled after repairing oil leaks (none so far) and it all works well. Just never let it idle in neutral.
	Posted on: 2008/7/12 22:09
	_________________ 1985, Performance Chip, hole in muffler, and other Mods
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88BlackZ51	Re: 6 Speed manual Trans S-640 Replacing a 4+3	#62
Senior Guru 481 Posts Member since: 2008/10/2 8:40	Central. So I cant use a bellhousing from a 89-91? If so why not?
	Posted on: 2009/5/26 12:49

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anesthes	Re: 6 Speed manual Trans S-640 Replacing a 4+3	#63
Master Guru Boston, MA 646 Posts Member since: 2008/6/18 18:02	Oddly enough, I did a clutch on my '96 Z28 last week and didn't bother measuring the thickness of the flywheel. stupid ass. -- Joe
	Posted on: 2009/5/26 18:35
	_________________ '79 Z28. 412 CID, NP 833 transmission, 3.73 10.5" rear end.
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CentralCoaster	Re: 6 Speed manual Trans S-640 Replacing a 4+3	#64
Senior Guru San Diego, CA 9454 Posts Member since: 2007/10/28 0:00	Quote: 88BlackZ51 wrote: Central. So I cant use a bellhousing from a 89-91? If so why not? The 89-90 bellhousing should work. I'm not sure why I removed that from the list. I also don't know what effect the slight difference would have on the clutch engagement. A slightly thicker bell (+1/10") means the fork pivot is pulled back slightly, meaning the fork is at a steeper angle, meaning there's more preload from the clutch slave, less fork travel, and slightly less force on the pressure plate. All of this is depending on flywheel as well. Some have said it even fits the old 84-87 starter. Obviously if you have a 89 flywheel and 89 bellhousing, it should function no different than any other 89 did off the showroom floor.
	Posted on: 2009/5/26 19:26
	_________________ 1985 Z51, ZF6
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88BlackZ51	Re: 6 Speed manual Trans S-640 Replacing a 4+3	#65
Senior Guru 481 Posts Member since: 2008/10/2 8:40	Quote: CentralCoaster wrote: Quote: 88BlackZ51 wrote: Central. So I cant use a bellhousing from a 89-91? If so why not? The 89-90 bellhousing should work. I'm not sure why I removed that from the list. I also don't know what effect the slight difference would have on the clutch engagement. A slightly thicker bell (+1/10") means the fork pivot is pulled back slightly, meaning the fork is at a steeper angle, meaning there's more preload from the clutch slave, less fork travel, and slightly less force on the pressure plate. All of this is depending on flywheel as well. Some have said it even fits the old 84-86 starter. Obviously if you have a 89 flywheel and 89 bellhousing, it should function no different than any other 89 did off the showroom floor. Thanks. I am just trying to figure what I need to fit the black tag ZF in my 88 car.
	Posted on: 2009/5/26 19:47

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CentralCoaster	Re: 6 Speed manual Trans S-640 Replacing a 4+3	#66
Senior Guru San Diego, CA 9454 Posts Member since: 2007/10/28 0:00	You have the 1-pc seal crank. So your crank flange should be in the same spot and fit the same flywheel options as any other 89-96 car. I believe your 88 also would have the ministarter.
	Posted on: 2009/5/26 20:08
	_________________ 1985 Z51, ZF6
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88BlackZ51	Re: 6 Speed manual Trans S-640 Replacing a 4+3	#67
Senior Guru 481 Posts Member since: 2008/10/2 8:40	Quote: CentralCoaster wrote: You have the 1-pc seal crank. So your crank flange should be in the same spot and fit the same flywheel options as any other 89-96 car. I believe your 88 also would have the ministarter. It does have the mini-starter? I wasn't quite sure. So do you know exactly what I need, and where I can order this stuff? I have a funny feeling the 4+3 won't last long behind the 421.
	Posted on: 2009/5/26 20:36

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88BlackZ51	Re: 6 Speed manual Trans S-640 Replacing a 4+3	#68
Senior Guru 481 Posts Member since: 2008/10/2 8:40	Also Kevin... Do you know the weight difference between the 4+3, and the ZF6?
	Posted on: 2009/5/26 20:47

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CentralCoaster	Re: 6 Speed manual Trans S-640 Replacing a 4+3	#69
Senior Guru San Diego, CA 9454 Posts Member since: 2007/10/28 0:00	I haven't weighed them, but the ZF6 is considerably heavier. I would guess 20 lbs extra based on picking them up.
	Posted on: 2009/5/26 22:45
	_________________ 1985 Z51, ZF6
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CentralCoaster	Re: 6 Speed manual Trans S-640 Replacing a 4+3	#70
Senior Guru San Diego, CA 9454 Posts Member since: 2007/10/28 0:00	This list will help you with the salvage yards. Most people find it interesting that with exception of 92-93, every year uses a different combination of parts! So yeah, L98 ministarter was 88-91. In 92 they changed it, but it's still a minstarter. I think I'm still running a 88-91 starter. The LT1 starter fit with a little massaging to mount flush against my starter pad because my block has the 3 holes and some webbing between them. At some point GM changed this. The LT1 starter sucks though because the terminals are a little further away and almost impossible to reach with the stock battery cable. Attach file: clutchpartslist.gif (24.83 KB)
	Posted on: 2009/5/26 22:46
	_________________ 1985 Z51, ZF6
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