The Stovebolt Site Forums The Shop Area Driveline Custom rear motor mounts TH700R4

Mating a th700r4 to an early 235 and installing in a '48 2 ton.

I'm making up the new rear cross member for the trans mount. Next will be making the new rear side engine mounts, since they were on the old bell housing.

I'm guessing I'm not the first person to do this. Does anyone have pictures of how they did it?

I'm keeping the original (but new) rubber mounts on the same frame location.

Thanks

with the trans bolted on the rear and the engine mounted toward the front, you do not want a 'middle' mount at the bellhouseing, so NO "rear" engine mounts, or rather the trans mount is the rear mount - hopefully you have the side [front] 235 mounts

Bill

No, I said early, center front mount.

I thought it would be easier to adapt the rear side mounts than change the front around.

If anyone says changing the front is easier, I'm listening.

I have been toying with the same idea on my pickup. I have not talked to Steve at Buffalo Enterprises, but have been told by several people, including Tom Langdon, to give Steve a call because he may have a solution.
To do what you want to do, you have to have an adapter plate and Steve at Buffalo makes them. It is possible he makes one or can make one with acceptable mounts to "replace" you current belhousing mounts.

I can't say changing the front would be easy, unless the engine has the provision for that, but you do not want the drive line fixed at 3 points, front/center/rear, it might work for a while if they're all aligned perfectly, but eventually something will break .... OTOH, I think the original front mount and the automatic tail mounts are too far apart, same situation with my TF trucks and the 'bird leg' front mounts for the 283 .... how did the factory mount the Hydramatic equipped AD's?

Bill

I would recommend using the side engine mounts if your engine has the mount bosses. As Bill stated there would be too much distance between the standard front mount and the rear transmission mount. I have seen people make this mistake with
V-8 conversions by using the existing front mounts and a rear trans mount. It usually results in broken mounts and everything flopping around. In some cases the only thing containing the engine is the exhaust system. Danchuk makes a bracket kit (for cars)for those inclined to use the aforementioned set up. It mounts from the frame horns to the bell housing and apparently keeps stuff in place.
Fred

Since the block doesn't have provisions for front side mounts and the existing cross member wouldn't align with then, I ruled that out. The 700R4 with the short tail shaft has a good mount right behind the pan and I don't think that span is too much.

I agree a pair of mid mounts could cause problems with weight distribution.

What I did was add was add a single torque stop mount.

I moved one of the bell housing mounts further up on the side of the original cross member. I chose the passenger side because that is in compression from the torque roll. The position and mounting angle makes it perpendicular to the thrust line of the engine under torque. I then welded up a bracket to attach to the transmission to adapter mounting bolts.
The addition of single mid mount doesn't cause weight distribution problems (3 legged stool) and transmits the torque to the frame to keep the block stable.

http://s1276.photobucket.com/user/jsdesign2/library/?view=recent&page=1

The top member of the bracket was left long for now because I will be building a mounting adapter for the hand brake and might need another support point. If not I will trim it.

When I remove everything for paint and powder, I am installing a safety cable across the rubber mount. If it collapses it will just lay on the frame like any other motor mount. However there would be nothing to keep the motor from tipping the other way if it separated. The cable will be the backup.

Hi Jim,

A couple of questions if I may...

Is that an adapter from Langdon's? It looks like the one I am using on my conversion - I'm adapting a 700R4 to my (1957) 235 in my '37 pickup.

I was told that "plenty of folks" have done this modification (including removing the main transmission support X-member) but the thing that bothers me is that I do not believe that the original engineers ever intended that much weight to be supported by the bolts that hold the transmission to the back of the block. That's why they designed a true three-point mount (front of engine, front of trans, rear of trans).

I'm still in the process of re-engineering and am looking at your bracket with interest. It it hard-bolted to the transmission or do you intend a cushion mount?

~rocker~

Hi Rocker,

Yes that is Langdon's adapter.

The '48 had a front center motor mount on the front cross member and a pair of rear mounts on the bell housing and resting on the 2nd cross member. The 4 speed transmission hung off the end with no mounts.

In the 50's the 6cyl changed to the same configuration as the V-8's, two front mounts a few inches further back on the block and a single transmission mount.

I don't actually remember working on a car with 4 motor mounts and a transmission mount. Large diesel trucks, yes. Some straight 8's has 2 front and 2 bell housing and no transmission. I'm sure someone will point out some.

Anyway, Langdon's adapter is held to the block with 6 grade 8 flat head bolts. More than sufficient.
The transmission is held to the adapter by 6 - 3/8" user supplied bolts. Grade 5 would be fine.

The adapter is aluminum and I'm sure Langdon would have used a T-6 grade. 5/8" thick again, more than sufficient for road use, up to the full capacity of the truck. If you were going off road I would upgrade to cast steel.

The bolts holding the transmission to the adapter have 5/8" thread engagement. This a good amount, but if you wanted a belt and suspenders, use grade 8 bolts that are 3/8" longer and put a jam nut on the engine side of the adapter (no washer).

My problem was front and rear center mounts and no side mounts. Nothing to keep the block from falling over and no torque transfer to the frame. This is how most new front wheel drive cars with transverse engines are mounted. That's why most have a top mount between the engine and firewall/frame.

The bracket I added is hard mounted to 2 transmission mounting bolts. The bottom of the bracket bolts to the original bell housing mount relocated higher on the 2nd cross member. This rubber mount provides the isolation.

This transfers the torque to the frame and actually supports a percentage of the engine weight when under load.

The 3rd cross member I added to hold the transmission mount is 1-1/2" x 1-5/8" .125" wall square. The end plates are mounted to the walls of the frame, not to the bottom.

Probably a bit long answer, but almost 30 years as a design engineer, occupational hazard.

Here's an idea for you, automatic trans side mount kit from Danchuks. Will not be a bolt in, but an idea in any case, similar problem solved re. 55 56 & 57 Chevys with less than optimal factory side trany mounts.
http://www.danchuk.com/ItemForm.aspx?Item=870

Jim - thanks for the detailed explanation - I do appreciate it!

It sounds like the difference between the way Chevrolet engineered my '37 and your '48 is that my features a cross-member for the rear of the transmission - right under the u-joint. It doesn't look like it carried much of the weight - that was handled by the bellhousing supports.

For my project when I removed the bellhousing I needed to cut the transmission X-member for clearance. I stubbed it just in case I figured out a method of attaching to the 700R4 or the adapter:

http://i1098.photobucket.com/albums/g369/J-reb/1937_Chev_Pickup/Trans-Adaptor1_zps876e3fc1.jpg

Then I removed the rear X-member and channeled it so that the 700R4 would fit. Amazingly it still fits up to the original frame mounting points!:

http://i1098.photobucket.com/albums/g369/J-reb/1937_Chev_Pickup/X-Member1_zpse07f1f37.jpg

Here's it all painted and ready for installation:

http://i1098.photobucket.com/albums/g369/J-reb/1937_Chev_Pickup/X-Member2_zpsdbbeb668.jpg

I still need to address the torque issue so I'm going to scrutinize your photos some more!

Thanks for the link - I'm going to give this a close look ;')

Rocker

The 2 ton has a 2 piece drive shaft. There is a cross member about 2 ft. further back that the center bearing hangs from. That takes away any loading from the rear axle and drive shaft.

The clearance is close on the cross member/transmission. After all is finished I might have to add a little relief.

Frame is going out for powder this week. Then I can start putting it together for real.

Good luck.