Hi everyone,
Two issues if I may,
A). I get a very loud vibration and noise when I back off the throttle after doing about 70-80 mph, (3,000 -3,500 or so rpms. The U-joints are good, the center bearing and related parts are new, the trans mount is also good, and the rear end is also good. I did use sections of driveshaft from two different sources when putting in my od trans though. So...I am assuming that the driveshaft is not balanced. I took it out and re-aligned the two halves 180 degrees, but that just slightly changed the rpm and loudness of the vibration.
Am I correct it is the drive shaft? Is there something else I should check?
Is there any way to check or balance the shaft w/o taking it to a shop?

and...
B). I would like to put in a 164 motor mount as a trans. mount but when checking my tranny mount I noticed on the 142 that the holes for the bolt ends are smaller and there doesn't seem to be as much room. My thought is to drill out the bolt holes slightly and cut the mount bolts just a bit so it will fit, (with the bolt ends the 164 mount looks too long to fit between the trans and that folded end on the cross member). Has anyone done this?

any input, suggestions, or opinions?
Thank you,
Chris

You say the vibration changed but didn't improve with a 180° change in
the driveshaft. Do you have the splined slip joint aligned so the yokes
are together like this:



If not, that could be your problem. If they are not aligned right the shift
in rotational velocity is NOT canceled out and you'll get a 1 or 2 per rotation
pulsation in the drive train.

I have put 164 rear mounts in 122s and 140s both. It is pretty tight but you
can do it. Loosening the front motor mounts where they bolt to the frame will
give you a bit of slack. Also you can loosen the crossmember on both ends and
take the vertical bolts out (tranny supported by a jack) to get the mount in
and then pry the boltholes into alignment with an alignment tool (a long skinny
punchlike tool) and put one bolt in while holding it with the tool, tighten the
first bolt and then put the second bolt in. Then tighten the bolts on the other
side.
--
George Downs Bartlesville, Heart of the USA!

Hi George,
Yes, I will double check, but I am pretty sure that I have the drive shaft aligned like that.

It's good to know that getting a 164 mount in there has been done. It looked tight but it is something I would like to do. I am going to change my current motor mounts to the 164 mounts also.One of them looks very tired, though not broken, so that may be the source of the vibration?
Thanks,
Chris

Hey Chris,

I used a 164 mount for the overdrive transmission on my 144. Without question, it is a great upgrade in my opinion. What a difference that one mount made to stiffen up the whole drivetrain. I will also use the 164 mounts on the engine from now on.

I didn't have to drill out the crossmember or the transmission mount.

I did shorten (cut) the studs that protrude from the rubber mount though to give me a little more working room.

I am not using a 140 w/ overdrive specific crossmember though. Instead I modified a non-overdrive crossmember.

Hopefully your vibration problem will turn out to be the engine mount.
--
Tom - '60 544, '68 220S, '70 145S, '86 745T, '06 Mazda MPV