Classic Audi Technical Mech/Tech Transmission » Problem with gearbox

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Old 11-04-18, 10:49 AM   #1
SPYROS29
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Default Problem with gearbox

Hello to the team,

I would like to post you my problem seeking for some answers from your valuable experience at classic Audis!
I have an Audi 80 typ 81 and last year I converted from 1.3 (EP engine) into 1.8 (DR engine). Also I changed the gearbox from the 4 gears 6V to the 5 gears ET.
My problem is this: The car runs fast with the first 3 gears and then falls gradually. I don't have the same torque on the 4th and 5th gears. Especially the 5th is like not exist. That means that I barely can achieve 150km/h.
I suspect that the problem might lies to the flywheel or the camshaft. What is your opinion?
I know for sure that the mechanic changed the flywheel during the conversion but I dont know what he put instead. Any suggestions?
I appreciate any proposal to solve the problem.
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Old 11-04-18, 06:01 PM   #2
4v6
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Start with the basics, Do a leakdown or compression test, check all initial settings like plug gaps, distribitor cap and rotor arm are correct, then check ignition timing and fuelling are all correct.

The flywheel wont have any effect on power output, the camshaft certainly will, so also try to ensure its the right one for your application.
What you will notice with a lighter flywheel is that acceleration in gear will be faster where a heavy flywheel will result in a slower in gear acceleration, thats due to it resisting being accelerated, refer to newtons laws of motion..
You wont have the same torque in higher gears as thats precisely what occurs when you make the gear longer, less torque but higher speed, lower gear gives higher torque but lower speed.

Make sure all the basic stuff is correct with the engine firts as its the source of all your power.
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Old 11-04-18, 06:40 PM   #3
SPYROS29
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Quote:
Originally Posted by 4v6 View Post
Start with the basics, Do a leakdown or compression test, check all initial settings like plug gaps, distribitor cap and rotor arm are correct, then check ignition timing and fuelling are all correct.

The flywheel wont have any effect on power output, the camshaft certainly will, so also try to ensure its the right one for your application.
What you will notice with a lighter flywheel is that acceleration in gear will be faster where a heavy flywheel will result in a slower in gear acceleration, thats due to it resisting being accelerated, refer to newtons laws of motion..
You wont have the same torque in higher gears as thats precisely what occurs when you make the gear longer, less torque but higher speed, lower gear gives higher torque but lower speed.

Make sure all the basic stuff is correct with the engine firts as its the source of all your power.
Thank you very much!
I have already done most of the things you proposed. I put the proper distributor plus the 1.8 inlet and outlet manifold. The main body of the engine was fully rebuild during the conversion and all the old engine flanges were replaced with brand new.
The only difference is that we replaced the original camschaft with the mechanic valves, with the newer audi 80 1.8 camschaft with the hydraulic tappets so that we dont have to adjust the valves in the future.
So far so good. I also checked that as long as I operated the car with the 4 gear box the car had much better top speed. When I changed it with the 5speed and the mechanic replaced the original engine's flywheel the car started to have this behaviour. I think that he didn't have to change the original flywheel as it is exactly the same to all 4 cylinder Audis of that era. And I believe that the problem lies there. Just to mention that the 3T gearbox is a mate with the DR engine. It is not an irrelevant gearbox and came off the same donor car.
I hope the problem lies there...otherwise I will have to seek for another engine

Last edited by SPYROS29; 11-04-18 at 07:16 PM.
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Old 11-04-18, 08:36 PM   #4
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Well, I doubt the flywheel theory very very much. Yes, lighter vs heavier flywheel makes some difference, but mainly where the acceleration is highest - in lower gears, and surely it shouldn't affect top speed. So either the gearbox is too long [which I doubt], or your new valvetrain setup sucks very badly, due to too mild camshaft, improper cam or ignition timing or something else.

In any case, in order to get more fun, I would suggest you to get some different engine indeed - either mk2 golf GTI 8v engine, or B2 DZ, or, if you aren't affected by increased taxes, which caused your car to have that damn VW engine in first place, 2.0 out of B3 A80 or B3/B4 passat or mk3 golf. 2.0 feels really good in car of such weight - I've such engine in a mk2 golf Alternatively, if you can make sure that compression ratio is ok, as found by some VW folks, it's enough to put GTI cam, dizzy [from K-jet engine] and some better carb, to have power of GTI.
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Old 12-04-18, 09:01 AM   #5
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Quote:
Originally Posted by msh View Post
Well, I doubt the flywheel theory very very much. Yes, lighter vs heavier flywheel makes some difference, but mainly where the acceleration is highest - in lower gears, and surely it shouldn't affect top speed. So either the gearbox is too long [which I doubt], or your new valvetrain setup sucks very badly, due to too mild camshaft, improper cam or ignition timing or something else.

In any case, in order to get more fun, I would suggest you to get some different engine indeed - either mk2 golf GTI 8v engine, or B2 DZ, or, if you aren't affected by increased taxes, which caused your car to have that damn VW engine in first place, 2.0 out of B3 A80 or B3/B4 passat or mk3 golf. 2.0 feels really good in car of such weight - I've such engine in a mk2 golf Alternatively, if you can make sure that compression ratio is ok, as found by some VW folks, it's enough to put GTI cam, dizzy [from K-jet engine] and some better carb, to have power of GTI.
I think that you are absolutely right my friend. I think that maybe he put the wrong cam into the cylinder head. Today I have the 026 103 373 Q cylinder head (from PM engine). I must have the 026 109 101 Q cam. If he put the 049 109 101 K cam from the DR engine then this is the problem. I will check this then.
Otherwise.......
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Old 15-04-18, 11:09 AM   #6
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Rather than wrong cam being the issue, most likely to have been timed up wrong, itll still run if its installed a tooth out of sync but itd create definite power issues.
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Old 15-04-18, 06:36 PM   #7
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Quote:
Originally Posted by 4v6 View Post
Rather than wrong cam being the issue, most likely to have been timed up wrong, itll still run if its installed a tooth out of sync but itd create definite power issues.
Thank you very much for the tip! I have already checked the timing when I replaced the distributor. So the last things to do are to check if the cam is the proper one, to put back the engine's own flywheel and then if the problem insists to change the whole cylinder head with the DR's original one. Fingers crossed then.....
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Old 21-04-18, 12:21 PM   #8
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Hello guys!

Finally, I solved the problem. I went to a different mechanic too....the one I made the final adjustments the other day.

We open the cylinder head and the cam was the right one! But the timing up was completely wrong. Two whole teeth late
Now the car is a rocket and accumulate km very fast with all gears!
Thank you very much all for your tips.
They saved my a....indeed!
Thank you all!

Last edited by SPYROS29; 21-04-18 at 01:38 PM.
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