Swapping a iron Eaton diff to an aluminum D44

[Kid Vette]

I'm in the process of swapping in an aluminum D44 to replace my iron Eaton diff. I did some measurements tonight.




I measured from the cover flange to the stub axles.



There is about 1/8" difference between the two. The D44 measures 2"; the Eaton measures 1 7/8".

I also measured the distance to the front pinion mount hole.



I held a level at the top of the hole on the Eaton and the drew a line at that level on the D44. The D44 is 1/2" lower.

So the distance from the pinion mount hole to the centerline of the stub axles is 5/8" less on the D44. So the pinion bracket on the frame should extend an additional 5/8" to locate the stub axles in the same position, right?

Beejay already ran into this when he did his swap. So I bought the section of frame off an 82 where the pinion bracket is welded on thinking I could just whittle it off and weld it on my frame - problem solved. But this is what has me stumped the bracket that I bought looks identical to the one on my frame now. So now I'm confused. Did they relocate the whole crossmember when they went to the D44?? :suicide:

 

[BBShark]

I think (from a birds eye view) the axles are not perpendicular to the chassis centerline.

 

[Kid Vette]

I think (from a birds eye view) the axles are not perpendicular to the chassis centerline.

That could be but I just want to get the stub axles in the same location they were in. I'm really surprised they changed so many dimensions when the went to the D44. Looks like I will need to extend my pinion mount by 5/8" and shorten my driveshaft 5/8". Why the heck would they move the pinion mount?

 

[Twin_Turbo]

Exactly, they are at an angle and so are the strut rods, that's part of why the axles are longer.

The best way to tackle this is to install the pinion mount and then mount the batwing brackets and weld them to the frame. DO NOT modify the pinion mount.

a little hard to see here, however you can see the pinion mount, it's identical to earlier. Go from there.... or you will end up like BeeJay and possibly having little spline engagement in the trans requiring a long DS

 

[Kid Vette]

Ok, i think I finally see what you guys are talking about. They left the pinion mount the same and moved the CL of the stub axles forward 5/8"!

Bad thing is my stub axles are going to hit the body if I do that. I found some pictures online which I think illustrate what they did with the body to clear for that.

Hers a 1973.

Here's a 1981.

 

[Kid Vette]

OK here's a pic of mine.



And here is a pic of a 80-82.



Its obvious they scalloped into the rear compartment to make room for the stub axles being moved forward. Its a relief I don't have to screw with the pinion mount but I have no experience doing glass work. Anybody have suggestions on what would be the best way to do this?

I looked in my battery box tonight and there really isn't much room.

 

[Twin_Turbo]

That's a very easy fix, cut both sides identical, flip the cut sections over and move them from side to side, that will plug your hole and give you the recess. The battery should fit fine, if anything there's more junk back there on 80-82 than on yours.

 

[Extreme Engineering]

Why not just extend the pinion mount and fab a longer driveshaft?

 

[Twin_Turbo]

That would mean he would have to fabricate new camber rods and a custom camber bracket since it's situated on the mating flange of diff and batwing. The holes in it are the same slots as used on earliier ones, arrangement is a little different. Would have to be modified for a 5/8 hole with some drilled out square plates so a bolt can go through andd the bracket hogged out. Then heims or roto joints and sleeves would make up the rest. You would not be able to use the 80-82 pieces if you more stuff.

 

[Kid Vette]

That's a very easy fix, cut both sides identical, flip the cut sections over and move them from side to side, that will plug your hole and give you the recess. The battery should fit fine, if anything there's more junk back there on 80-82 than on yours.

Great idea! But first I think I'm going to check with a local Corvette salvage yard and see if they have that section available. I'm still going to need some help on what materials and methods to use to bond it in. I'm totally clueless on fiberglass stuff but I guess this would be a good place to learn. Nobody will see it.

 

[Twin_Turbo]

check out stingers thread, or my thread about the 63 corvette resto or plenty other threads here. There are tons of pics and descriptions on fiberglass repair with all kinds of handy tricks. This is really easy to do, messy and itchy work but very easily done.

 

[Sam Cogley]

Not to take this too far afield, but what's the purpose of the swap? I know the aluminum housing and batwing are much lighter than the older-style parts, but that version of the D44 doesn't exactly get glowing reviews.

 

[Kid Vette]

My goal is 3k lbs and 400 HP. That would give me the same power to weight ratio as the old 289 AC Cobras. Just a goal I have set for myself.

This diff was built by Mike Dyer which included fitting one of his steel caps.



He says the diff should be good up to 400 HP so I'll be OK. Some guys are putting more horsepower with the stock caps with no problem.

Once I put on the aluminum heads and water pump I should be real close to my goal.

 

[JeffP1167]

I have the batwing mounts on frame sections

 

[Kid Vette]

I have the batwing mounts on frame sections

Thanks but I got the brackets from a1sensei when he parted out his Vette.



I would have had him cut out the body panel too if I knew I needed it then.

 

[mrvette]

I have the batwing mounts on frame sections

Thanks but I got the brackets from a1sensei when he parted out his Vette.



I would have had him cut out the body panel too if I knew I needed it then.

A1sensei, is that the fellow here in OP/Jacksonville?? I not seen him post anywhere in a long time now.....I met him a couple times some years ago, he had a Karate studio here .....

:friends:

 

[Kid Vette]

I have the batwing mounts on frame sections

Thanks but I got the brackets from a1sensei when he parted out his Vette.



I would have had him cut out the body panel too if I knew I needed it then.

A1sensei, is that the fellow here in OP/Jacksonville?? I not seen him post anywhere in a long time now.....I met him a couple times some years ago, he had a Karate studio here .....

:friends:

That's the guy. Somebody stole his Vette and wrecked it - bent the frame. I believe he's still Vetteless.

Sent fom my mobile using Tapatalk 2

 

[Kid Vette]

I was just thinking about why they would have moved the CL of the stub axles forward 5/8". Assuming the CL of the stub axles is now 5/8" forward of the spindles in the TAs; this would alleviate the toe steer problem, correct? At least in the first 5/8" travel.

So with this setup I would want the half shafts level rather than 1/2" higher at the differential like Greenwood recommended?

Sent fom my mobile using Tapatalk 2

 

[mrvette]

I have the batwing mounts on frame sections

Thanks but I got the brackets from a1sensei when he parted out his Vette.



I would have had him cut out the body panel too if I knew I needed it then.

A1sensei, is that the fellow here in OP/Jacksonville?? I not seen him post anywhere in a long time now.....I met him a couple times some years ago, he had a Karate studio here .....

:friends:

That's the guy. Somebody stole his Vette and wrecked it - bent the frame. I believe he's still Vetteless.

Sent fom my mobile using Tapatalk 2

SHIT!!! he is a nice guy too, called the school Christian Karate or something damn close.....

which is why I have a near fail proof anti theft system on my car....

man, I"d go near zirk zoid.....:shocking:

 

[Kid Vette]

I was just thinking about why they would have moved the CL of the stub axles forward 5/8". Assuming the CL of the stub axles is now 5/8" forward of the spindles in the TAs; this would alleviate the toe steer problem, correct? At least in the first 5/8" travel.

So with this setup I would want the half shafts level rather than 1/2" higher at the differential like Greenwood recommended?

Sent fom my mobile using Tapatalk 2

Well, this made a lot of sense in the shower this morning but not so much now. :huh2: I think it would help with toe steer but it seems like the effect would be minimal. :crutches: