Duetto Rear Trans Mount ? - Alfa Romeo Bulletin Board & Forums

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post #1 of 16 (permalink) Old 05-12-2017, 03:01 PM Thread Starter
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Duetto Rear Trans Mount ?

So a few weeks ago when my tech was installing new Miller's Classic Green gear oil in my trans, he notices that the rear trans mount looks poor at best. He recommended that we change it the next time up on the lift, so I ordered a new replacement mount from Classic Alfa in my last parts order.

For the last couple of years, I had noticed a bit of a growl from 5th gear occasionally, 1 thru 4 smooth as silk, no noises whatsoever. So I figure, maybe since my rear mount was bad, AND 5th gear is at the rear of the gearbox, maybe that is where my periodic 5th gear noise was coming from.... hey alignment is everything sometimes, right.

So this morning we change out the mount.... so on the way home...... 5th gear is now also smooth as silk... no noise or growl at al.... BUT I now have a bit of a vibration under the car at all times..... like the drivetrain is now back in alignment and the car doesn't like it ! My tech previously has checked my motor mounts and driveline doughnut and gave me the thumbs up..... so what gives ?

Let me know what you think, and thanks in advance.

Bob

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post #2 of 16 (permalink) Old 05-12-2017, 03:29 PM
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How is your middle drive line bearing? Maybe the bushing in it went soft like the rear mount? Now the tail of the tranny is stable and the bearing bushing is taking up the slop--or not. Was the new bushing identical to the old one? On some bushings the center pin hole sits higher or lower than the original throwing everything a little out of alignment. Just a couple of thoughts from your description--

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post #3 of 16 (permalink) Old 05-12-2017, 06:52 PM Thread Starter
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Middle drive line bearing and support was replaced 90 days ago....when the trans oil was dumped.

We didnt compare the trans mounts.... bagged one that came out was almost in pieces. Ordered the correct early 105 variant from Classic..... I assume their parts are well known/used all over. I have used quite a few parts and components from them over the years with zero issues. I do recall the cross member bolt lined up pretty close, and we did make sure the mount was oriented the correct way before pressing in.

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post #4 of 16 (permalink) Old 05-12-2017, 07:54 PM
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Yeah I haven't had an issue with classic parts. The old mount was probably taking the vibration out because it was so loose and now you can feel it in the tranny. I hate driveline vibrations. U joints? Sometimes they feel good from an inspection while installed but one of the cups dried out and causes vibration. And then there's ujoint out of phase. Did you break down the driveshaft when installing the mount?

BTW--did changing out the gearbox oil fix the problem you had with redline?

Frank Livesay Huntsville, AL
Green Alfa - 68 Canadian 1750 Spider Veloce (driver)
White Alfa - 68 Euro 1750 GTV (needs a refresh)
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post #5 of 16 (permalink) Old 05-12-2017, 08:00 PM
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The mechanical clutch cars use a stiffer mount than the later hydraulic cars. It allows less movement of the tranny but it is less tolerant of driveshaft misalignment. I have one in my 79 and in my opinion it is an upgrade but I had to spend a few hours measuring and correcting misalignment that was not apparent with the soft mount.

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post #6 of 16 (permalink) Old 05-13-2017, 06:45 PM Thread Starter
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Quote:
Originally Posted by flivesay View Post
BTW--did changing out the gearbox oil fix the problem you had with redline?
Yes... but had to flush twice and now running Miller Classic Green Gear oil..... back to normal.

Thanks,

Bob

1966 Duetto
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post #7 of 16 (permalink) Old 05-13-2017, 06:49 PM Thread Starter
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No did not break down the driveshaft when installing the trans mount.... but it was when the center support and bearing were changed not long ago.

I drove the car almost 100 miles to a show in the mountains today..... under 3000 rpm its not too bad.... above 3000 is another story.... but I agree, its somewhere in the drive line.

How can I be sure ?

Thanks

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post #8 of 16 (permalink) Old 05-15-2017, 03:43 PM Thread Starter
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UPDATE

I have driven the car a couple more times.... and the vibration is lessening, and the rpm range where there is a little remaining vibration is increasing....... it trying to go away on its own.

Is this possible......?

1966 Duetto
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post #9 of 16 (permalink) Old 05-15-2017, 04:24 PM
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Probably not!! Back to basics. Just because it was changed awhile ago doesn't mean that it can't be at fault. Rear/front wheel balance, u joint play, driveline out of balance, carrier bearing, flex donut, transmission mount. All need to be check for correctness.
Cheers, Jon
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post #10 of 16 (permalink) Old 05-16-2017, 07:07 AM
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Vibration

Several things have to be correct or they will cause vibration.
1- the driveline must be "in line" and often the engine & transmission isn`t aimed directly at the pinion flange. Correct by shimming the trans in the correct location. Pics of how to check this have been posted on the BB.

2- the pinion angle MUST match the angle of the front section of the drive shaft to phase the u-joint`s movements correctly.

3- the u-joints should be correctly aligned. If the splined joint was separated this could be the problem. There is only 1 correct fitment in this part, but it can be assembled in multiple incorrect positions.
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post #11 of 16 (permalink) Old 05-16-2017, 08:00 AM
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Originally Posted by oldcanuck View Post
UPDATE

I have driven the car a couple more times.... and the vibration is lessening, and the rpm range where there is a little remaining vibration is increasing....... it trying to go away on its own?
Probably not but this is the least expensive option. I'd give it a couple of thousand miles to see if the vibration continues to lessen.

Mark
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post #12 of 16 (permalink) Old 05-16-2017, 01:46 PM
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first thing I'd do in your position, is get under the car and check the alignment....as others suggest above!

diagram here that illustrates it:
Gearbox mount orientation

oh, and, don't forget to grease the slip (splined) joint...frequently, I do it every oil change at latest

Dom - Alfa Spider 1990 S4 - formerly: Alfa 101 Sprint, 2600 Sprint, Montreal - family classics: Jensen Interceptor II, '58 Hooper RR Silver Cloud I, Shadow II, '60 Corvette.
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post #13 of 16 (permalink) Old 05-17-2017, 04:53 AM Thread Starter
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I do know the splined joint on the driveshaft was marked prior to splitting apart to install the new center support and bearing. It has received a once a year greasing at minimum while I have owned the car.

Since this vibration continues to lessen... I am going to give it a little more time, but first chance I have to get it back up on the lift, I will have Skip check alignment of the driveline since I'm sure this is where the vibration originates from.

I think I am going to re-new the center muffler here soon, so this would be a perfect opportunity to check it.

I appreciate everyone's input.

Bob

1966 Duetto
1976 Spider Veloce
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post #14 of 16 (permalink) Old 05-18-2017, 07:33 AM
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How is that mount replaced with the transmission in the car? Is there a tool that "presses" the bushing out within the tranny tunnel? thx.
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post #15 of 16 (permalink) Old 05-18-2017, 08:27 AM
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Quote:
Originally Posted by hoodmeister View Post
How is that mount replaced with the transmission in the car? Is there a tool that "presses" the bushing out within the tranny tunnel? thx.
yes, the special tool seen here:
Replacing transmission mount

but a few things from the local hardware store does the same job!:
Trans mount

Dom - Alfa Spider 1990 S4 - formerly: Alfa 101 Sprint, 2600 Sprint, Montreal - family classics: Jensen Interceptor II, '58 Hooper RR Silver Cloud I, Shadow II, '60 Corvette.
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