Tremec install in a 65 Mustang fastback…
Ok folks… strap on you seat belts. Let me warn you right now, this is not for the faint of heart…
My donor car gave up its engine and the Tremec 3550 that I am about to install in the Mustang. The donor had seen better days and from the look of it, so had some of the other components of the car.
After much digging and question asking, I was not able to get a straight answer if the Tremec would fit in the 65. I got comments from that it would not fit, to it is a simple bolt in… it fits better than the T-5. I can tell you, both of the above statements are wrong!!! The Tremec will fit, but if you choose to use the aftermarket parts, you will never get a proper engine angle. The best you can hope for is about 6 degrees. Just to let you know, 3 degrees is the factory specification on engine angle. At 6 degrees, you will be replacing U-joints every 10k miles… Not something I wished to do…
Now for the bad news… To make it fit correctly, the back of the transmission needs to be raised about 2 inches above where it hits the rear cross member! First you will need to remove the existing cross member. Trust me, this gets scary from here on out…
After removing the cross member, It is time to put the trans back up in the car and scribe out the top of the transmission. After doing this, from the bottom, drill holes at each transition or corners, and then whip out he saber saw… Here is a picture of how far up the Tremec needs to come up to get a 3 degree tilt on the engine.
Well, since I had to do that much work, I decided to move the engine back ½ an inch. Think about this… I just moved close to 800 pounds of the car’s total weight to the rear ½ inch. This will provide much more improvement on handling than moving the battery to the trunk. Something to think about… The other benefit is that the transmission lines up with the existing shifter hole. Like that is a benefit =). Actually, it will reduce the reach to the shifter.
Here is a picture from the bottom of the car with the transmission in place. I still need to fabricate a new cross member, but that is coming soon, along with a new top to the existing tunnel and some new floor pans.
Note where the old cross member was. It really needs to be about 2 inches further back in order for the Tremec.
At this point, the car has turned into a street rod.
More progress. The meaty stuff… Next came the decision as to how to support the transmission.
An opportunity presented itself. Us the old double hump cross member from the 90!! So, step one is to fabricate new mounts to the subframes for the cross member. This was done by taking some 3/16 bar stock and cutting and forming ears to mount it to the subframe. Next, weld them in completely. Note: the floor pan in this picture had to be move up about ½ an inch to clear the hump on this side (passenger) Also, note above the cut line that was needed to clear the top of the transmission.
Here is the Driver’s side…
After forming the mounting locations, the next step was to fabricate the top of the tunnel that had to be cut out to clear the top of the transmission.
The tunnel had to be raised about 2 inches in order to get the proper clearance. After forming the 16gauge sheet metal, it was then spot welded into place. The welds have not been cleaned up in this picture, nor has the seam sealer been installed, after a liberal application of POR-15.
Here is a close-up of the transmission installed with the cross member out of the 90 LX...
Here is a picture from the back.
Do not let any one tell you that you can just bolt a Tremec in and not have to do any modifications.
Well, for the most part, the Tremec is installed. All that is let to do after the subframe connector install, is some cleanup, rust-proofing, and a little painting.
People may wonder why I chose to do all of this, well this link explains the main point of drive line angle and its effects. Free Driveline Assembly Troubleshooting Information Keep in mind that drive shaft RPM is the same as engine RPM in your 1:1 gear such as 4th gear on a 5 speed. The driveshaft RPM on a set of 4.11s at 70 MPH is almost 4000 RPM! That is the reasoning behind going to all of this effort. I want a car that will be vibration free well over 70 MPH.