TCCoA Forums banner

1 - 10 of 10 Posts

·
Registered
Joined
·
1,996 Posts
Discussion Starter #1
There has been some threads about this subject, but stuff isn't adding up. While poking around SCP, it shows drive shafts that cross reference a Thunderbird AND a Mark VIII. It also looks like haf-shafts are the same as well, based on part numbers. The rear differential pinion brace is also listed for both applications.

I am looking to put 3.73s in my Thunderbird. I was wondering if I can get a whole axle and swap it out. I was also looking for confirmation that there are indeed 3.73s in there.

On another thread, someone said..

-- It's not a drop in unit for a IRS rear end, there is no grove in the end gears to lock in the CV axles.
and..

he Gears for the axles need a groove machined in for the spring clip on our (IRS) axles; the Straight axles use a circlip and a flat washer...no groove...

Our axles aren't able to come out, due to the suspension design, so there is no need for a solid lock at the end of the axle.

Get whoever is doing the mark parts swap to machine it for you.
Has anyone taken a good look to see if this is do-able? There are also weight savings swapping the axles and of course, I want to take advantage of that.

What do you guys think?
 

·
Faster than Porkchop
Joined
·
2,037 Posts
Yes, they should work for both Tbirds and Mark's . I used a pumpkin from a 99 Cobra they too have a IRS .
 

·
Registered
Joined
·
623 Posts
I'm not entirely sure about what you're asking, but... Between Mark VIIIs and Thunderbirds/Cougars the entire housing (center section) with gears, diff., etc. inside will interchange with no modifications necessary.

Step 1: Remove center section from Mark VIII
Step 2: Remove center section from Bird/Coug
Step 3: Do nothing to your fancy aluminum Mark differential/gear/housing assembly (assuming you're keeping the lame stock gears), do nothing to your Bird/Coug
Step 4: Bolt Mark center section into Bird/Coug

The side gear questions you have are in reference to the difference between the side gears in a solid axle differential and an irs differential. This will only come into play if you acquire a solid axle differential out of a mustang, etc. A good route to go is to acquire a used Mark differential housing (they're all aluminum), get a trac-lok differential (preferably an irs one, but I run a solid axle one with no issues), get some gears, and assemble and install them in your car. I'm not sure how much weight I shaved off, nothing to get excited about though.
 

·
Registered
Joined
·
1,996 Posts
Discussion Starter #4
I am just trying to see if we can take a Mark VIII axle and put it into the Bird. My whole goal is to put 3.73s in. We are thinking it would be a short cut if the Mark came with them, plus the extra bonus of having the weight savings.
 

·
Registered
Joined
·
623 Posts
Our cars do not have a 'proper' axle. In the middle there is a differential housing, sticking out from that on each side is an axle shaft. These axle shafts pass through wheel bearings on each side pressed into the spindle. The 'axle tube' on our cars is a cylinder of air surrounding the axle shafts.

Marks did not come with 3.73 gears. Their diff housing is Al opposed to our Fe housing. This is where the weight savings comes in. I don't know the precise difference in weight, I did not put mine on a scale. This info is on this site however.
 

·
Registered
Joined
·
171 Posts
I think the M8 diff housing weighs about 2/3 of the T'bird/Cougar one. You could rebuild the M8 with 3.73 and trac-loc out of the vehicle and when you got ready, you could just pop it in. You can use the solid axle side gears, BUT, you will have HELL getting the 1/2 shaft stubs out unless you remove the diff cover and remove the c clip from the stub. I think 95badbird just left the clips off and just stuck them in and let it ride.
thats how I run mine.....mustang diff, no clips.
 

·
Registered
Joined
·
1,996 Posts
Discussion Starter #7
Thanks for the posts. I think I am just going to get the 3.73s installed and call it a day. I found a place to do it for me.
 

·
Premium Member
Joined
·
9,165 Posts
I'm doing this week exactly what you said you wanted to do. I bought a worn out Supercoupe center section with a 3.27 trac-loc in it. Then I bought a set of 3.73 gears, and then found a Mark VIII aluminum Case. Took those to a builder along with the kits for rebuilding the trac-loc and the rear end. When its done I'll just swap it into the car.. (hopefully this weekend)
 

·
Registered
Joined
·
1,996 Posts
Discussion Starter #10
Good luck with that! Let us know how it goes. I came pretty close to buying your 3.55s but after doing some research and asking around, it looked like 3.73s was the right way for me to go.
 
1 - 10 of 10 Posts
Top