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Opeler
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Has anyone had an Opel 4-speed transmission which works ok on first gear, but on 2nd and 3rd gear somehow always fails at 4000-5000rpm when accelerating? I've not tested how 4th gear works on high revs. Acceleration slows down noticeably and car just doesn't sound as healthy as usual (sorry I can't describe it well) when engine should give its best torque.
I first experienced this problem after changing transmission which makes me suspect that. (But the old trans was so poor I always was very gentle with it.) However, it doesn't make any noticeable noise, shifting works always very well and my friend who sold it said he never had a problem with it but he didn't have a tuned engine then. I changed transmission oil after buying it and didn't notice any metal particles in the old oil.

I looked at transmission forum but didn't find anybody reporting problems like this. Performance of the car is quite poor: engine should have at least 120hp (dual carbs, ported head, hot street cam, etc. there should potential to 140hp, likely more) and rear tires are 215/50 R13 but best 0-100km/h acceleration time I've measured was 12.5 seconds! :( Luckily it works better when accelerating 80km/h -> 110km/h on 4th gear, for example. I guess other parts to suspect would be fuel system or rear exle.
 

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That is unusual, I would look at timing and resync of the duals first. Fuel pressure may be an issue to look into as well.
 

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It sounds more like an engine/carb problem than a transmission problem. Who installed your setup? Maybe because you "babied" the last tranny your never got to see that the setup wasn't correct for higher revs when running with a good tranny. I would go over everything again from the carb and engine setup and bet you will find your problem there.
 

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I have problems that have some similarity to this problem.

My Gearbox works fine in 1st and 4th. But in 2nd and 3rd it makes a squealing sound, the problem started after I have the gearbox taken out to change some clutch parts. And when i put it in again, there was some noise from the gearbox when driving, And after about a week the described sound came

Can anyone help me with a solution, what have i done wrong?
 

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If the problem persists after checking your fuel delivery/ignition, double check your four transmission bolts. If these have backed out, you'll lose 2nd & 3rd, then eventually 1st and 4th as the transmission torques around.

But again, check your fuel & ignition systems 1st as these areas are much more likely, and prone, to fail.

One other area to check; with the engine off, have a buddy press the accelerator to the floor while you look down the carb. I've found that the funky linkage on Opels can be out of adjustment and your secondary may not be opening all the way.
 
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