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Rear Motor Mounts


keithb7

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Hi folks. While tranny and clutch are out in my ‘38!, I am planning to replace the motor mounts. The two rear are seen here. They are rotten.

Mounting bolts are out. Bottom rubber easily removed. 


 I’ve not done this job before. It seems to me I need to jack up the rear of the engine a little to get the bell housing up?  To probably give enough clearance to get the upper rubber mounts out?  Am I on the right track here? 
 

Are their other parts I should be loosening before I lift the rear of the engine? Suggested jack point on engine? Thx. 
 

 

447B00BD-04DD-4952-8D06-B63F6E0267DC.jpeg

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Do you have a manual?  There is a difference between the drvr side and pass side that has to do with where and which direction the metal washers fit.  Put a piece of two by four between the back of the oil pan and lift the rear of the engine.  Have some one watch the fan to radiator clearance because if you Jack to far to can push the fan into the core. Once you have the bellhousing up, you may need to rock it side to side with a pry bar to get the bolts out and then again when reinstalling.

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Thanks Greg. You eased my mind before I started jacking it up. 
 

 I had built a couple pilot studs to guide the tranny back in without putting any load on the pressure plate. As per the ‘38 shop manual. I threaded them in place, and  I put some blocking under them and jacked up. 
 

Mounts came our pretty easily. Right one is broken. I’ll clean it up and weld the tube to the washer.  Old  mounts were in very poor condition.  Glad I did this. 
 

Both rear mounts appear identical. I’ll check my manual to be sure. 
 

 

780B3080-D5C0-4891-A5C3-199BAE63F5A9.jpeg

Edited by keithb7
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Do not over tighten the new ones.  Snug and a nother half turn.  If you get them too tight they will transmit vibrations, and being too tight will shorten their service span.  The guide pins are a good idea when I did mine I pit them in the opposing diagonal corners.  Also use Allen head cap bolts with washers.  The Allen's on a couple extensions were easier to get the threads started with out worrying about potentially cross theading them. The top ones can be a pain even with the floor pan out.

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3 hours ago, keithb7 said:

Hi folks. While tranny and clutch are out in my ‘38!, I am planning to replace the motor mounts. The two rear are seen here. They are rotten.

Mounting bolts are out. Bottom rubber easily removed. 


 I’ve not done this job before. It seems to me I need to jack up the rear of the engine a little to get the bell housing up?  To probably give enough clearance to get the upper rubber mounts out?  Am I on the right track here? 

Are their other parts I should be loosening before I lift the rear of the engine? Suggested jack point on engine?


This thread may have some useful info:


https://p15-d24.com/topic/50844-engine-mounts-p15-caution/?tab=comments#comment-539481

 

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@greg g I spent time today going through every shop, and parts manual that I have here for several cars between '38 to '54. Also my Motors manuals. I can't find any info, instructions, or illustrations on these rear motor mounts. Your illustrations are helpful, but I am not sure what I am to learn form this. I'm not grasping something here, I think.

 

It appears both of the images in your illustration are labeled as left rear.

 

What are they implying when they say "add rubber insulator to left rear motor mount only"? I have an upper and lower rubber motor mount for the left, and right. Am I supposed to round up some other rubber insulator? Perhaps parts were missing from my mounts?  Below here is a pic one of my rear mounts, with all the pieces lined up, as it came out.

 

As mentioned, no diagrams and no instructions to reference. Thanks.

 

 

IMG_5455.jpg

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48 minutes ago, keithb7 said:

@greg g I spent time today going through every shop, and parts manual that I have here for several cars between '38 to '54. Also my Motors manuals. I can't find any info, instructions, or illustrations on these rear motor mounts. Your illustrations are helpful, but I am not sure what I am to learn form this. I'm not grasping something here, I think.

 

It appears both of the images in your illustration are labeled as left rear.

 

What are they implying when they say "add rubber insulator to left rear motor mount only"? I have an upper and lower rubber motor mount for the left, and right. Am I supposed to round up some other rubber insulator? Perhaps parts were missing from my mounts?  Below here is a pic one of my rear mounts, with all the pieces lined up, as it came out.

 

As mentioned, no diagrams and no instructions to reference. Thanks.

 

Keith,

 

In my 1946-54 Plymouth Service Manual the illustration posted by greg g along with the description is in the engine section, page 151. If I recall correctly, beginning in the early '50's the additional rubber washer was added to prevent the left mount bottom metal washer from touching the frame during hard acceleration as the engine torques to the right. I doubt the little Six in your '38 will develop enough torque for this to be a problem.  :)

 

I recommend you read all the thread I linked earlier in this thread for a lot of info about the mounts. I ended up deleting the bottom mounts in order to eliminate harsh vibration. Many aftermarket mounts are made of rubber that is too firm.....this is discussed in the thread I linked. There is a lot of confusion about the mounts, the ones we purchase now do not resemble the lower mounts in the manual illustration. Also detailed in my thread.  :)

Edited by Sam Buchanan
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All chrysler and desoto cars and most dodges use the two lower thick rubber donuts with a taller matching washer "T-tubes" ....that being a 3" welded washer and tube assembly

The washer T-tube is pushed down into the top of the upper motor mount .

Then that mount assembly is set into the cross member...the bell housing rests on the two mounts.

The lower under side rubber donuts are then pushed up onto the protruding steel motor mount washer T-tubes.

The bolts dropped down through the bell housing and mounts...then the large 3" steel washer,  lock washer and nut are installed and tightened...TIGHT!

The original two factory rear mount bolts and T-tube washers are a specified length/height. That being so when the mount bolts are bolted tight they cannot crush the rear mounts so tight that a vibration occurs.

On the plymouths mopar cheaped out on most models..not all and did not use the  thick lower rubber donuts.

Instead they only used that 1/8" lower 3" diameter anti-clunk or vibration prevention washer. Once again the correct  dimensions of OE bolts and T-tube washers and factory correct height top mounts all need to be used to prevent crushing tight the rear insulator mounts.

The left rear engine mount rises when accelerating hard from a start..the reason for the 1/8" +   rubber washer on the drivers side only.

The bigger and heavier FD engines supposedly needed the full upper and lower soft rubber mounts.

The plymouths didn't.

I have seen original p15's though with upper and lower mounts.

As long as the right soft mounts, non damaged washer T-tubes of the correct height for the type of upper lower mounts you can install any style of rear mounts aand not crush them tight.

Remember that driving over rough roads also causes the trans and engine to bounce up and down on that rear cross member...so properly assembled rear mounts will prevent the excessive drive train motion and keep it noise and vibration free.

I'm done?

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Hi Dodgeb4ya,

 

I'm not sure what you mean by "T-tubes" ....that being a 3" welded washer and tube assembly.

 

I'm having my engine rebuilt ('39 Ply) and have purchased new upper and lower rear mouths, washers, and bolts. These are all separate parts. I haven't taken off the old mounts yet. Should there be a tube that the bolt fits in that is welded to the washer?

 

Attached is a scan of the rear mount parts for the 1939 Plymouth Passenger Car Parts List.

 

Pete

 

2020-01-26-0001.jpg

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As for 39 Plymouth's I am not familiar with them too much...

There are several different rear motor mounts used by Chrysler corp through the years all slightly different...

Welded one piece washer T-tube washer...that's what I call them is also shown...

The makers of mounts today don't know all the different styles hardness and sizes of these rear mounts. They mostly make one that kinda fits IMO.

Motor Mounts Chrysler and Plymouth.JPG

Motor Mounts Chrysler and Plymouth (4).JPG

Motor Mounts Chrysler and Plymouth (3) - Copy.JPG

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@Sam Buchanan I read your earlier post about motor mounts thoroughly. I too have a pretty stiff set of modern production “good enough” mounts. I am planning to not install the lowers as you did. 

Am I to just install the washer and nut as seen here? The lower washer does not contact the cross frame member at all. It bottoms out on the inner center metal spacer tube seen in pic 1. Is this correct? Nothing else needed here? Thanks. 

 

 

963E164B-25E2-4B93-9B21-4BE01D192C27.jpeg

7D40D7B6-D9DD-4A12-9085-D89FBE41AC70.jpeg

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Keith, that’s how my mounts are installed and the engine is smooth. I haven’t detected anything that feels like the bottom washer touching the crossmember. The tranny just rides on the upper mount.

Edited by Sam Buchanan
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Ok Thanks.

 

 I guess I won't want to take the car over any jumps. Upon landing, the tranny and rear engine may rise up...On second thought that would probably be the least of my concerns. LOL

Edited by keithb7
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Ok Thanks.

 

 I guess I won't want to take the car over any jumps. Upon landing the tranny and rear engine may rise up...On second thought that would probably be the least of my concerns. LOL

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10 hours ago, keithb7 said:

Ok Thanks.

 

 I guess I won't want to take the car over any jumps. Upon landing, the tranny and rear engine may rise up...On second thought that would probably be the least of my concerns. LOL

 

As you are doing your best Dukes of Hazard imitation the tranny would only rise up enough to pull the lower washers against the cross member, maybe 3/16"? You'll need to be more concerned about how Daisy critiques your driving technique.  ?

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@Sam Buchanan I am not sure about the motor mounts I used. They seem to be making noise still, even though I left the lower mounts out. The upper one the left side did not set down nice and flush. The right one did. I am going to see what else I can do. Maybe take it back out some day and try reshaping it a little with a dremel or something until it sits flush in position. After completing the tranny job, I think I could get in there and re & re a mount pretty quick now. It's a shame that new parts today for our old Moparare made to a crappy standard and considered "close enough" or "good enough". It's unacceptable as I paid to get those mounts from a supplier and I paid dearly for the freight to get them here. They're fodder.

Edited by keithb7
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On another forum I was just reading about how the big block mounts for musclecar era Mopars are made wrong.

 

We are reaping the results of sending our manufacturing overseas.  I suppose an opportunity for a cottage industry type operation to make the correct mounts has arisen.  Though to be honest I would have no idea how to do them. 

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25 minutes ago, keithb7 said:

@Sam Buchanan I am not sure about the motor mounts I used. They seem to be making noise still, even though I left the lower mounts out. The upper one the left side did not set down nice and flush. The right one did. I am going to see what else I can do. Maybe take it back out some day and try reshaping it a little with a dremel or something until it sits flush in position. After completing the tranny job, I think I could get in there and re & re a mount pretty quick now. It's a shame that new parts today for our old Moparare made to a crappy standard and considered "close enough" or "good enough". It's unacceptable as I paid to get those mounts from a supplier and I paid dearly for the freight to get them here. They're fodder.

 

Keith, you should be able to jack up the tranny enough to slip the mounts out to replace them. However, I don't know the solution for obtaining a mount with the proper resilience, may take some experimentation. I've seen Chrysler mounts with holes drilled in them, might be worth getting a couple extra next time you order some parts and try modifying mounts until you get what you want.

 

Congrats on the trans overhaul and getting your neat car back on the road!

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The mounts with the holes in them are generally found on the DeSoto and Chrysler Six Cylinder heavier FD cars.

They are also soft pliable rubber.

Recently pulled a set out of a 50 Windsor.

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  • 2 years later...

My new to me 47 Dodge D25C (Canadian model) seems to be a hybrid following some of comment above.

Dodgeb4ya and others have provided great explanations.

My problem started with the proper fan belt rubbing on the upright that holds the front engine mount/insulator.  The previous owner installed a narrower belt to overcome this.  This skinny belt rides in the bottom of the groove which is less than ideal.

Looking down at the pulley on the engine I can see the groove is partially obscured and using a straight edge it shows that there is no clearance between the edge of the correct belt and the upright mount.

The real problem as I see it is that the engine has shifted a few degrees to the drivers side and is no longer perpendicular to the crossmember or the upright.  The car has never been in a collision but I thought after 75 years something else must be worn or broken.

It turns out that the often mentioned left rear mount is worn to the point where the bolt is near the back of the opening.  This would explain the shift off the engine to the left.  The other mounts of the same age are worn as well.

On both the left and the right rear mounts there is no lower rubber cushion.  Whether there ever was or not is unknown but the length of the “T” tube indicates there may have been.  The nut that goes on the bolt that passes through from the top has a bevel washer ahead of it and it tightens against the tube.  However the bolt is still loose.

Comments in the many threads indicate that this is the case to prevent the rear from jumping out of position and that the weight of the engine and transmission simply holds everything down.

I’m thinking that since the T section seems long enough to accommodate a lower mount that there should be one there, even if it is just to prevent side to side movement of the bolt.

Some of the photos in the threads no longer load so I am unable to see what they were showing.

My questions are:

1)  What is the actual clearance measurement between the side of the OEM 5/8” belt and the upright for the front motor mount?

2)  While waiting for an answer from AB about the differences between part # L-348 and L-346 Rear Upper Engine Mounts as well L-347 and L-349 Rear Lower Engine Mounts as they all state they are for Dodge and 1947.  Does someone know which are the correct ones?

3)  Is L-338 Front Engine mount the correct one?

I need to figure out how to reduce my photo size before aI can post them.

 

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