Lumina Z34 Transmission issues

[d12x12d]

I just bought a 1992 Chevy Lumina Z34 with the 5-Speed manual transmission with only 63 ,000 miles, it needed a windshield, fuel pump, i replaced the plugs and wires. When i finally took it out for a test drive the gears would grind as im shifting normally, but if i waited for a couple minutes and then shifted it seemed to be fine . i did some research on older transmissions and i believe i need to use the double-clutch method, seeing as ive only encountered newer manual transmissions, i was hoping to encounter someone who knows around what rpm i should be shifting at in each gear as not to grind the dog teeth
-thanx

[Tinman238]

Double clutching is a techique needed for REALLY old transmissions. Your transmission is a fully sychronized, modern transmission. Specifically, it is a Getrag 284 transaxle.

Check the fluid level in the transmission and make sure its the correct type. GM recommends manual transaxle oil no. 12345349, or equivalent. You might want to drain and refill it to make sure its the right type, and to get rid of any contaminants (including metal shavings). The manual calls for 2 quarts.

If all that checks out, make sure the clutch is fully disengaging when you shift. If the clutch hydraulic system (master cylinder and slave cylinder) doesn't have enough fluid, or the system has air in it, the clutch won't completely disengage and you will have a tough time shifting and will wear out both the transaxle and the clutch.

[blazes9395]

I agree with tinman, flush out that fluid and replace it with fresh fluid and see how it goes. Also, you have quite a rare car on your hands with a manual trans, 3.4 engine for '92.

[jeffcoslacker]

Yeah you are either not getting a full release outta the clutch or the synchros are not working right...that car has obviously sat around a lot, do what the others suggested and it may improve with some road time as well...

In the mean time if it resists shifting you can float gears without the clutch if you are really good with a manual gearbox, but learning to do it usually involves a lotta metal trauma and I don't advise it...unless the car belongs to a relative you hate or something

Basically the theory is on the upshift you anticipate what rpm the engine would sound like in the next higher gear for current road speed and allow rpm to drop down to that range, pulling the shifter out of the current gear when the torque on the driveline is minimal, then guide it to the next gear gently and if you matched rpms right, it'll drop it easy...if not, it will grind or crunch, and maybe knock a tooth or two off...

Downshifts are a little harder to master, the procedure is reversed, so when downshifting on decelleration you bring the rpms up slightly as you pull the shifter out of gear, anticipate the higher rpm in the next lower gear, and try to get the shifter to drop in...it's tricky...I've driven cars and motorcycles home with no clutch many times, so it's a useful skill, and makes your friends think you are some kind of machine god

Anyway, if double clutching seems to produce a smoother gear change, the problem is that you are either purging a small amount of air from a hydro clutch by pumping (in which case it's leaking somewhere) or you are forcing sluggish synchros into action...true double clutching with a car tranny produces no effect if you aren't floating the ranges as I described above...double clutching simply breaks the torque on the driveline momentarily and allows time to rev-match...

[d12x12d]

Well, I finally changed out the tranny fluid, did some other minor repairs, took it for a test drive and it still grinds with the clutch fully depressed. Talk about rare, after some research it turns out there were only 200 Luminas manufactured with a manual transmission, furthermore there was only around 900 of the Getrag 284 transmissions made. Every tranny shop I've called has told me that they cant service it. I'm kind of in a bind because part of the frame of my daily driver basically just broke (long story). I guess the next step would be to find a transmission that would bolt up? I was really hoping to avoid doing that :/. Oh, and I have barely any expirience with manuals, so floating gears wont work too well. Thanks guys

[john51md]

Originally Posted by d12x12d

Well, I finally changed out the tranny fluid, did some other minor repairs, took it for a test drive and it still grinds with the clutch fully depressed. Talk about rare, after some research it turns out there were only 200 Luminas manufactured with a manual transmission, furthermore there was only around 900 of the Getrag 284 transmissions made. Every tranny shop I've called has told me that they cant service it. I'm kind of in a bind because part of the frame of my daily driver basically just broke (long story). I guess the next step would be to find a transmission that would bolt up? I was really hoping to avoid doing that :/. Oh, and I have barely any expirience with manuals, so floating gears wont work too well. Thanks guys

Well, you could find a wrecked Z34 with a good auto and change it over...
and if you want to find out what will fit, try www.v6z24.com.. these guys swap everything into Z24's 3.4's, 3.8's all kinds of 5 speeds from diff Chevys, they can tell you what might be a doner car for a tranny for yours.

[j cAT]

replace clutch fluid old fluid will not work as well........

[loosenut74]

Ok.... 16 years old, 63,000 miles and no one has mentioned that maybe the clutch master cylinder might be bad?... I would start off by replacing that... if that dont work, replace the "slave" cylinder <---long as your doing the "slave replace the clutch, pressure plate, pilot bushing and resurface the flywheel, but do yourself a favor replace the clutch master cylinder first, i bet that solves your problem... but thats just the words of a 20 year A.S.E. certified mechanic...