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OPEL-LESS!!!
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2,116 Posts
Discussion Starter · #1 ·
is there any way to tell what the gear ratios are in a stock 4 speed transmission for a GT? or are they all the same? i have to change the transmission in my car because its noisy and pops out of 4th gear all the time. it did 3500 RPM at about 70 mile an hour is this about right? i'm hoping i can take numbers off the transmissions and compare the gear ratios to see if i'm goin higher or lower gear....i have a few transmissions to choose from so i can get the gears i want hopefully unless they're all the same.........thanks in advance for any input.
 

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Detritus Maximus
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2,839 Posts
As far as I know, all American 1.5/1.9 Opel transmissions are the same. The only thing that changes is the rear end ratio in the other Opels (but not the GT).

3500 rpm at 70 is right for a stock opel trans and 3.44 rearend with approximately stock tire size.
 

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OPEL-LESS!!!
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2,116 Posts
Discussion Starter · #3 ·
so i'm not goin to change my gears transmission or rear end wise with the stock GT parts i have laying around?
 

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Detritus Maximus
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2,839 Posts
Not a sausage. A 1.5/1.9 Kadette rear axle will bolt right in (unless I have my info wrong). They have a couple benefits, one is they are equipped with sway bars and the Rallye has the 3.67-1 rear ratio. The disadvantage is they have (at least the early ones) 'c-clip' rear axles. A little 'c-clip' holds the axle in the housing. Break one and the axle comes right out.
 

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OPEL-LESS!!!
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2,116 Posts
Discussion Starter · #5 ·
ya i know what happens when a c clip breaks.......cousin races factory stocks at the local 3/8 mile track and out came the left rear witht he axle and all and then the next thing you seen was a 75 monte carlo on it roof. anyway got my transmission in last night along with the new clutch kit and finally took it out today. seems to be the same gear ratio but the speedo dont think so. it had all 1972 drive train in the car when i got it. fan blade to tailshaft. now it has all 1970 drivetdrain from fan blade to tailshaft and thats what it should have. but the where the speedo goes into the tranny is on the opposite side of the car as the previous transmission and cable would not reach. so i used the gear reducer i belive thats what it is anyway to make my cable reach and now the speedo says 55 at 3500RPM cant be right. any ideas on how to fix that. changing the speedo gear? i have a few trannys left over and the one that used to be in the car had a blue gear so should i make sure i still have a blue gear in the tranny?
 
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