Author Topic: Big Block Trans Crossmember (Read 286 times)

JDM4401 · « **on:** January, 04, 2010, 07:11:10 PM »

Before I install the engine and trans I have been going through all the parts I have collected to make sure I have everything. Last week I found out that my shifter is mounted using the incorrect mounting plate. I ordered the correct plate, but another issue came to light. I don't have the correct trans crossmember. I bought a crossmember well over a year ago that was advertised as a four speed crossmember for a 67/68 mustang. Now that I am aware of there being two crossmember's I have one for a small block.

So other than Mansfield Mustang does anyone else sell them? I thought about modifying mine, but I really don't know how much lower the transmission needs to sit. Has anyone ever modified or made their own trans crossmember for a big block application and want to share how they did it?

95GT · « **Reply #1 on:** January, 04, 2010, 07:40:31 PM »

I also was not aware that there is a difference. I will be going through the same as you are. Can you tell me what the difference between the big block and the small block are? I may have to start hunting also.

JDM4401 · « **Reply #2 on:** January, 04, 2010, 08:13:42 PM »

The big block crossmember hangs lower than the crossmember for a small block. If a small block crossmember is used the shifter will contact the trans tunnel because the entire trans is higher than its supposed to be. You could trim the hole in the trans tunnel so the shifter will not contact it, but that is not a good idea for two reasons. One your hacking up your car and two the driveline angle is changed, which isn't good either. I have talked with one person who said they have used the incorrect crossmember without any probelms, but I would rather do it the correct way.

The big block crossmembers are stamped with 390STD on them, but I have read there are other crossmembers that will. I understand Mansfield Mustang sells the crossmeber we need.