Engine alignment? - Alfa Romeo Bulletin Board & Forums
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post #1 of 25 (permalink) Old 01-02-2017, 04:10 AM Thread Starter
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Engine alignment?

I think that my engine may be sitting too high at the back. I fitted an early gearbox bush and it went in slightly twisted (ie rotated by a around 10į off centre. The fan is touching the bottom of the radiator shroud wich makes me think that it is maybe too low at the front/high at the back. All of the engine mounts are new. I also have a transmission vibration which could maybe be from the donut having to flex?

Should the early and late gearbox bushes put the gearbox at the same height relative to the mount? Is there a datum point to check how the engine is sitting?

If this is the problem, would be ok to use longer bolts and packing pieces to drop the gearbox mount (I guess by around 10mm)?
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post #2 of 25 (permalink) Old 01-02-2017, 06:00 AM
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Quote:
I also have a transmission vibration which could maybe be from the donut having to flex?
The vibration may be from U-joint mis-alignment if the engine is tilted so much. Shimming the rear mount bracket with washers may be necessary to align the U-joints but 10 mm is a lot. I suspect that there is a cause for the tilted engine. When the suspension is normally loaded the front section of driveshaft should be parallel to the input shaft of the differential. I posted my alignment method a few days ago in one of the threads about the one piece carbon fiber driveshaft.

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post #3 of 25 (permalink) Old 01-02-2017, 06:36 AM
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What year car, and which trans mount did you use? Can you post a pic? You got it in right way up? Lots of them get installed upside down.
Is the radiator the right one for the year, and the shroud too? Plastic shrouds get mangled, bent over time, especially across the bottom.
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post #4 of 25 (permalink) Old 01-02-2017, 08:19 AM
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I think you are saying that you installed one of these:
instead of one of these:

If that's the case, the earlier mount would drop your transmission - not raise it - since the later mount goes in with its bolt hole oriented below its center (e.g., as pictured above). I'm not saying that your engine-trans isn't misaligned; I'm just questioning whether the incorrect trans mount could be the cause.

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Originally Posted by tomcotez View Post
I also have a transmission vibration which could maybe be from the donut having to flex?
Might be - donuts weren't designed to flex. And as alfaparticle wrote, U-joints are also sensitive to the relative axes of the transmission and differential.

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post #5 of 25 (permalink) Old 01-02-2017, 08:32 AM Thread Starter
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Yes, thatís the one. I assumed that they would work out more or less the same level as the late type mount must spring down a lot under the weight of the transmission given how little rubber is in there.
Yes, Iím pretty sure the radiator and fan shroud are original or at least original spec.
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post #6 of 25 (permalink) Old 01-02-2017, 08:41 AM
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Yes, that’s the one. I assumed that they would work out more or less the same level as the late type mount must spring down a lot under the weight of the transmission given how little rubber is in there.
You're right - the later mount will settle, shifting its bolt hole towards the center (similar to the hole's location in the earlier mount). In fact, as the later mounts become old and oil-softened, they will usually collapse, shifting the bolt hole upward, which drops the transmission. All that is probably what motivated you to substitute the earlier mount.

I guess my point was that substituting an earlier mount for a later one shouldn't raise the transmission.

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would be ok to use longer bolts and packing pieces to drop the gearbox mount
Yea, that's a good idea. It can't hurt anything and will help isolate the problem; if the vibration goes away with the transmission lowered, you will have learned something.

Jay Mackro
San Juan Capistrano, CA

'65 Guilia Sprint GT
'67 Duetto
'91 164L

Last edited by Alfajay; 01-02-2017 at 08:47 AM.
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post #7 of 25 (permalink) Old 01-04-2017, 02:51 AM
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Just an info, but I'm sure you know :

Did you used the correct center bearing in the transmission ?

If the bearing is too thick, you have vibration.

Now, the supports for trans and gearbox are directly screwed onto the chassis, contrary to 750 and 101 series fitted with washers between them.

Good luck.
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post #8 of 25 (permalink) Old 08-17-2017, 01:23 PM
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I have a vibration in the same general vicinity that comes on at 40 mph then goes away. Then comes on again at 60mph and up and I don't quite know how to eliminate it.
I have new u-joints, new support and bearing and flex joint. U-joints are in phase and when the flexj was installed I didn't remove the metal band until after the ds was in place. I have since removed the ds to have it balanced but when I got to the shop they didn't have the correct fixtures for the transm side to hook it up.
So, I remounted the ds. My GTV6 buddy said that one must use a hose clamp and crank down the flexj so that the bolts will move back and forth freely in their respective fittings. Once that is in place you can tighten them all down. So I wrapped a 5 1/2" clothes dryer hose clamp around the flexj and tightened it till it started to skip then tightened the six nuts. I could not get the bolts to move freely fore and aft before tightening. The vibration is gone from 40 mph. In fact, it is as smooth as silk but comes on at one click after 60mph and sticks around as I accelerate. I can modulate the vibration with the foot feet.
I am going to try to find a more heavy duty hose clamp but may have to pull the whole ds again. Anyone had this problem? Am I moving in the right direction? TIA db

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post #9 of 25 (permalink) Old 08-17-2017, 07:24 PM
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C'mon y'all. Show me some love........
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post #10 of 25 (permalink) Old 08-17-2017, 07:48 PM
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If you got the bolts in ok I don't see how the method of installment has anything to do with the vibration.

Ed Prytherch
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2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #11 of 25 (permalink) Old 08-17-2017, 08:47 PM
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Is the splined slip joint between the front and rear section of the d/s worn out? Do you have flat washers between the three bolts heads and three nuts where they touch the flex joint? Is the exhaust/trans bracket properly installed? (is the exhaust touching something somewhere?) I know you said the U-joints are phased properly, did you keep all of the d/s pieces in exact the exact alignment to themselves as found when initially removed from the car, or are some of the pieces 180 degrees out?

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post #12 of 25 (permalink) Old 08-18-2017, 09:05 AM
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alignment

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Originally Posted by alfaparticle View Post
If you got the bolts in ok I don't see how the method of installment has anything to do with the vibration.
My GTV6 friend, who obviously has a totally different driveshaft configuration, was only suggesting that in his case, when he had the flex joint compressed correctly so that, when installing the ds, the bolts slide into place without being encumbered by the flex joint, he was able to eliminate ds vibration above 60mph.
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post #13 of 25 (permalink) Old 08-18-2017, 09:28 AM
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I would be looking at the olive on the trans output shaft and the bushing in the driveshaft.

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post #14 of 25 (permalink) Old 08-18-2017, 10:15 AM
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Originally Posted by rogerspeed View Post
Is the splined slip joint between the front and rear section of the d/s worn out? NO, I DON'T BELIEVE SO.
Do you have flat washers between the three bolts heads and three nuts where they touch the flex joint? NO, NONE OF THE SIX DO. 3 CONNEC THE FJ TO THE TRANS YOKE AND THREE CONNNECT THE FJ TO THE DS/UJOINTS. THEY ALL HAVE SELF LOCKING NUTS.
Is the exhaust/trans bracket properly installed? I DIDN'T INSTALL IT THE MECHANIC THAT REBUILT THE ENGINE IS AN ALFA GUY. DEFINE PROPERLY? WHAT SHOULD I BE LOOKING FOR THERE?
(is the exhaust touching something somewhere?) NOPE
I know you said the U-joints are phased properly, did you keep all of the d/s pieces in exact the exact alignment to themselves as found when initially removed from the car, or are some of the pieces 180 degrees out?
I KNOW THE REAR IS NOT 180 OUT BECAUSE I MARKED IT WITH A FILE YEARS AGO WHEN I HAD U JOINTS REPLACED. AND I MARKED THE FORWARD PIECES WITH WHITE OUT WHEN I TOOK THEM OUT A COUPLE YEARS AGO WHEN I STARTED THE REBUILD. I APPRECIATE YOU GUYS GETTING BACK TO ME.

See my reponses in the quote above.

Last edited by dlbehrns; 08-18-2017 at 10:18 AM.
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post #15 of 25 (permalink) Old 08-18-2017, 03:26 PM
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hope you find the problem. by the factory instruction, using nylock nuts on the six bolts securing the the donut, where the donut touches either the bolt head (three) or nut (three) there should be a flat washer. no washers are used where the donut touches and secures to a flange. this way when tightening the nut (or bolthead) it is not twisting (distorting) the donut.

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