Interference between transmission and brake cross-shaft

Al 29Tudor

Al 29Tudor

Well-known member
Just installed a newly built rear end with a Mitchell and noticed binding with brake peddle all the way down. No wheel brake rods are attached yet but while looking for the interference noticed that the cross shaft actually raises the transmission a tiny bit. There are four depressions in the top of the cross shaft from the contact so it has happened before.
Maybe when the rods are attached and adjusted there will not be any interference.
Anyone ever of this happening?
Thanks,
Al
 
Your rear motor mounts may be cracked and out of shape if they are the original style. If they are the after market motor mounts with the rubber pucks, the pucks may need replacing.


Tom Endy
 
Also, if you have a Float-a-Motor rear mount, or decide to install one, there is a yoke that bolts to the clam shell and supports the rear of the transmission/engine assembly.

It's shown here at the rear of the transmission, with a rubber insulator on the cross member.

It may help.
 

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Not related to the above question but I just wanted to say thank you for the photo of the rear rubber mount.Have been tearing my hair out for days trying to figure out to fit the thing...a picture is worth a thousand words.cheers Vic
 
My first Model A, many years ago, the brakes worked OK but it was very hard to push the brake pedal. One day I noticed that when I pushed the brake pedal the transmission lifted up a bit. After I fixed the rear motor mounts the brake pedal wasn't so hard to push.
 
Thanks for your input everyone.
There isn't any obvious frame sag as the hood lines are even.
I've looked at the rear mounts and nothing is obvious but I'm planning to order the rubber kit on Monday just in case those rubber parts are compressed. It does seem there is some space at the top of the rubber to the under side of the mount.
As for the Float-A-Motor I've never wanted to change from the original design but that rear bracket that supports the ****** from the frame is interesting. Even though after market I'm giving that more thought along with replacing the rubber parts.
Al
 
Al, some early 29's had a lip on the top part of the u-joint housing. It rested or had a gap between it and the crossmember. If you use that part of the float-a-motor, you will have to cut it off and grind down to get the float-a-motor housing to fit. I did all of that and wish I had left it alone because I went back to original mounts.
 
The early u joint cover with the hook should be above the cross member, and not resting on the lip. Mine has a good 1/4" to 3/8" gap.


I'd look for frame sag as the cause of the problem. My friend had the same problem, and once the frame sag was fixed, the brake cleared fine.
 
If the float-A-motor rear mount yoke pictured in post number 4 is used it will raise the transmission and torque tube so that it doesn't drag on the service brake cross shaft even if the rest of the float-A- motor kit isn't even used and even if the frame is sagged . If the float-A-motor kit is used without the rear mount it will eventually float the complete running gear . In other words without the rear yoke assembly the motor and transmission can slightly move when the brakes are applied .
 
1955cj5 and Purdy,
Did you guys find the rear transmission to frame mount separately or do you have to buy to whole kit?
I want to use the stock mount with new rubbers and this transmission mount.
Thanks,
Al
 
I bought the whole kit at the same time.

You might try Steve at Bert's...he may have just the yoke....

1-800-321-1931

They are closed on Monday's...



.
 
I also bought the whole kit . I don't think that the rear transmission mount is sold seperately . A lot of people leave this part off . you may have some luck finding one by advertising in the parts wanted section on this site. I found one at a swap meet and installed it on a car with a sagged frame and it served the purpose well
 
Thanks guys.
I ordered the set today and will have it on Wednesday along with new rear engine mount rubber parts.
Looks like it will go a long way toward taking some of that cantilevered load of the ****** off the engine mounts.
 
As said by others, usually interference of the brake cross shaft is caused by frame sag at the motor mounts.

When I restored my 30 Coupe I checked the frame before setting the body on and found 1/4 inch sag in the frame on the driver side and 3/16 inch sag on the passenger side at the motor mounts.


After straightening the frame there was no more interference of the cross shaft and had full brake pedal movement.

This is a common problem, after many years with the engine and transmission weight of 475 pounds, to cause the frame to sag at the motor mounts.

Ron
 
Most body shops have floor tie downs that can be used to straighten frame sag . If a person has a cross tie or I beam that is long enough to chain down the frame , front and back and use a bottle jack to jack up the frame , under the rear motor mounts they can straighten the frame themself .
 
Update on the issue:
I bought the rubber pads for the original mount and the Float-A-Motor package.
I decided not to use the rubber pads since it looked like a lot of work and I was concerned that I might need a frame spreader and they looked as thick as the old ones.
Here is the good part - I used the transmission yoke with a washer under the plate allowing for less compression and less lift of the motor. I just wanted to take some of the load of the ****** off the engine mounts.
The way that worked out was just what I wanted.
Now I have the rest of the Float-A-Motor kit that's not needed and would like to sell.
If anyone would like to purchase just the rear engine mount components with all the hardware still in sealed bags that would be good.
Al Leach
941-497-4747
al.leach3@gmail.com
 
Y-Blockhead thanks good idea
Never posted there and spent 20 minutes looking for how to create a swap meet post
so I posted a question to the boss
 
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