C4 to long tail shaft BBF C6 swap.

[Tataocb]

I am trying to figure out the best way to swap my C4 for the long tailshaft C6 I got to go with the 460 motor. I know I have the option of swapping the tailshaft for that of a short tailshaft C6, but the transmission show would charge $200. I could try doing it myself, but I have never messed with transmissions, and it seems you have to pretty much take everything out of the case to remove the pin which holds the output shaft. So I am looking for alternatives to mount the C6 as is and cut the driveshaft.

I have measured the distance from where the bellhousing meets the block plate to the transmission mount holes and it is 20" for my C4, it is 22" for a short tailshaft c6 and 25" for a long tailshaft C6. Since I am looking into keeping the long tailshaft, I would need to move the transmission mount holes 5 inches towards the back. These measurements are give or take 1/4".

The way I see it, I have 3 options:

1. Move my current crossmember mounting place 5" back and get a C6 crossmember. The car has a piece of metal on each side going from the frame rails to the tunnel. The crossmember bolts up to the ends of each of these pieces of metal. I was told they are called "ears". I believe those are welded in place. So those would have to be cut out and rewelded 5 inches towards the back, and then install the C6 crossmember.

2. I dont know if this is possible, but was thinking of just welding a plate to my current crossmember, where the tranny mount goes, to "extend" that part of the crossmember 5 inches towards the back, drill new holes at the end of that plate, and bolt the transmission mount onto the end of that plate. I would also need to take measurements to make sure that the C6 won't bump into any part of the 5 inch plate.

3. Buy a universal crossmember and have that installed in the correct position to line up with the C6 long tailshaft tranny.

Here is an image where I try to explain what I mean. I am not sure if I should post here or in the Chassis subforum. What do you guys think?

 

[turtle5353]

Get a big block c4 bellhousing. http://m.ebay.com/itm/FORD-BIG-CASE-BIG-BLOCK-C-4-BELL-HOUSING-/182032048627?hash=item2a61f4a1f3%3Ag%3AaecAAOSw%7EOVWymPU&_trkparms=pageci%253A274e6142-09b8-11e7-80fe-74dbd1803d68%257Cparentrq%253Ad382598315a0a60ce0c9abe7fff7bedc%257Ciid%253A1

 

[Tataocb]

Get a big block c4 bellhousing. http://m.ebay.com/itm/FORD-BIG-CASE-BIG-BLOCK-C-4-BELL-HOUSING-/182032048627?hash=item2a61f4a1f3%3Ag%3AaecAAOSw%7EOVWymPU&_trkparms=pageci%253A274e6142-09b8-11e7-80fe-74dbd1803d68%257Cparentrq%253Ad382598315a0a60ce0c9abe7fff7bedc%257Ciid%253A1

I thought about that, but my C4 is the case fill version, so the bellhousing is not removable. I would need to get a pan fill C4 transmission in order to swap the bellhousing; or get a JW bellhousing. Both options would probably cost over $400. I figured moving the crossmember and shortening the driveshaft would be less expensive.

 

[73pony]

How are your welding/fab skills? I would suggest option 4. Fab up an entirely new trans mount that would mount in the stock location but be set up to accept the long tailshaft C6 and shorten and balance your driveshaft.

 

[flstf09]

Why not just get the correct c6 crossmember?

 

[Tataocb]

How are your welding/fab skills? I would suggest option 4. Fab up an entirely new trans mount that would mount in the stock location but be set up to accept the long tailshaft C6 and shorten and balance your driveshaft.

Sadly, I don't know how to weld at all.

That is what I am trying to achieve with option 2. Leave the "ears" in place and using a plate welded to the current mount location, extend the transmission mount location 5 inches back.

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[73pony]

Not sure they make one for the 71-73 mustangs for the C6 with long tailshaft.

 

[Tataocb]

Why not just get the correct c6 crossmember?

I believe the "ears" are not in the correct place to just swap out the C4 crossmember for a stock C6 crossmember, as the stock small block C6 mount holes are 2" further back. Unless of course, the stock C6 crossmember moves the tranny mount holes 2 inches back from where they are located using a C4 crossmember.

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[73pony]

All 71-73 mustangs have one place to attach the transmission crossmember, but different crossmembers to accommodate the different transmissions offered. The only C6's offered in the 71-73 were short tailshaft. I am not sure I would trust welding an extension plate on a stock crossmember, especially with the 460 in there. If your welding/fab skills are not up to the task maybe see if a local shop can fab one up for you. I did a quick search online and do not see that anyone offers one for the long tailshaft. If you have the stock crossmember and know exactly how much farther back the holes need to be a good fab shop should be able to make you one or alter your stock one in a way that is more durable and safe then just welding an extension plate on it.

 

[flstf09]

I'm gonna have to measure my tails haft now.

 

[Tataocb]

This is what a guy did in a different forum with this same transmission using a stock C6 crossmember from a 351C car. If the "ears" are in the same location for both C4 and C6 Mustangs, then stock C6 crossmember moves the mounting holes 2 inches back, so I would only need an extra 3 inches.

 

[73pony]

I just read your first post again. $200 to have the trans shop swap out the long tail shaft for the short one is not bad at all. I think you will have more money in trying to have a custom cross member fabbed up.

 

[TommyK]

I just read your first post again. $200 to have the trans shop swap out the long tail shaft for the short one is not bad at all. I think you will have more money in trying to have a custom cross member fabbed up.

+1

If you can't fabricate and weld yourself then swapping the tail shaft or finding a complete short tail shaft BBF C6 and buying the correct factory cross member are your best options.

 

[Tataocb]

What if I get a stock C6 crossmember and weld a 3 inch plate to it similar to what the guy in the pictures did? He fabricated the tranny mount and welded that to a plate that wast hen bolted to the crossmember. I have the original tranny mount, so would technically only need a 3 inch extension plate welded to the stock C6 crossmember to bolt the original tranny mount to. Would this be a feasible option?

Mathematically, the way I see it is:

Tailshaft swap option = cost of C6 crossmember + $200

Plate option = cost of C6 crossmember + cost of fab/welding the plate.

So if welding the plate costs less than $200, then I would end up spending less. I am trying to keep the cost as low as possible, but still be safe.

 

[73pony]

What if I get a stock C6 crossmember and weld a 3 inch plate to it similar to what the guy in the pictures did? He fabricated the tranny mount and welded that to a plate that wast hen bolted to the crossmember. I have the original tranny mount, so would technically only need a 3 inch extension plate welded to the stock C6 crossmember to bolt the original tranny mount to. Would this be a feasible option?

Mathematically, the way I see it is:

Tailshaft swap option = cost of C6 crossmember + $200

Plate option = cost of C6 crossmember + cost of fab/welding the plate.

So if welding the plate costs less than $200, then I would end up spending less. I am trying to keep the cost as low as possible, but still be safe.

As I stated earlier. I would not trust a 3" extension plate welded to the crossmember with a small block. A big block NO WAY!! Plus you are going to have to pay someone to cut and fab the plate then weld it to the cross member and will likely have over $100 in that unless you have friends. You are talking a difference of less than $100 for a safety concern. IMHO.

 

[Don C]

Swapping in AODs and AODEs have similar issues. Maybe this article will give you some ideas:

http://diyford.com/ford-aod-transmission-installation-and-swapping-guide/

 

[Tataocb]

I will probably reconsider buying a JW Bellhousing then. The tailshaft swap ($200) + C6 Crossmember ($115 from Crites) + Shortening of the driveshaft ($100) is a little over $415.

If I go with the C4 and the bellhousing swap, would I also need to change the torque converter and flywheel? I believe I read somewhere else that people run into issues with the torque converter when using a C4 with a 460. Are all C4s the same total length? If I get a C4 from a 351/400 modified, would it require changes to the driveshaft? I have read somewhere that the pan fill version is a couple of inches shorter than the case fill (which is what I currently have).

I know I ask a lot of questions...haha...I am just trying to consider all possibilities before committing to one.

 

[Don C]

The link I posted yesterday has a table that shows the lengths. Pan fill is longer.

 

[Tataocb]

The link I posted yesterday has a table that shows the lengths. Pan fill is longer.

Thanks. The firewall at work blocks the page. I will pull it up in my phone when I get a chance.

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