Removing the diff cover in an SPF

[Tinker51]

Anybody removed the differential rear cover from an SPF car.
How far do I need to disassemble to make this work?
Just a quick look this afternoon looks like removing the rear mount, removing the driveshaft and releasing the two front mounts to slide the whole assembly forward enough to get the rear cover off.
Anyone done it another way?

[rob frink]

..........

[bobcowan]

If you just want to remove the cover, no need to pull the axles out.

Getting it back on can be a bear. You don't want it sliding around and making a mess with the silicone sealant. Get a couple of 1" 5/16 bolts and cut the heads off. Cut a screwdriver slot on the end. You can use them as alignment studs for the cover.

[Lowell W]

I concur with Rob and maybe with Bob...however...It isn't THAT hard to get the axles out and drop the punkin and you would get a much better view of whatever it is you're looking for. I'm not altogether sure there's room behind the diff in the SPF frame to get the cover off and look in there and I think it would be tight and messy to replace the cover. On the other hand, you may be correct and be able to slide everything forward and get more room.

If you remove the rear wheels, hubs, rotors and calipers, then pull the lower arm Allen bolts and the axle nuts, you can press the axles out of the hubs, swing the hubs up out of the way and pull out the axles. Four bolts hold the driveshaft to the flange and 4 more bolts hold the diff in the car. Be careful not to pull off the breather tube, which is zip-tied to somewhere on the frame, and you can lower the diff out.

Please let us know what you find.

Thanks,

Lowell

[RedBarchetta]

While you have it out, you may want to consider adding one of these:

http://www.steeda.com/products/cobra...over_brace.php

It's an easy bolt-in (in the car...you don't have to pull the whole unit out) and gives you some peace of mind. I installed one, but all my photos are on my home PC. I also modified (re-drilled) the rear mount so that the differential is 1/2" higher and gives the half-shafts a little more clearance to the frame members they pass through.

You should also consider drilling and tapping the lower case for a drain plug. Randy posted a good procedure for this on SCOF that you can do with the differential in the car. Much easier if you have it out and apart.

-Dean #747

[rob frink]

..........

[Tinker51]

Rob,
No need to remove the axles as I am merely replacing the rear cover which has a crack in it and seeps oil. It looked like I should be able to get the clearance needed by releasing all mounts then supporting and sliding the assembly forward just a couple of inches and thanks for reminding me. I need to stop off at Ford and get some friction modifier.

Bob,
That bolt thing is a damn fine idea! Thanks for the tip!

Lowell,
I saw the breather tube on the new cover so I am aware of it but thanks for the heads up.

Dean,
That piece is very interesting. I will look into it as that is pretty much the reason I am replacing the cover but nowhere near as drastic as the one pictured.

Everyone,
Thanks for your input.
Sam.

[Lowell W]

Dean, Sam, et al.,

Just looked at the Steeda brace. I have the diff back in the car now but I could always add it later. I'm wondering, though: on our cars, doesn't the brace have to go to the outside of the channel the rear cover extension slides into? Does that still allow all the holes to line up or did you make some mods to something? Can you install this without having to drain the diff?

Wish I had noticed this sooner.

Lowell

[RedBarchetta]

Lowell,

I'll try to upload some images tonight so that you can see my install of the Steeda brace.

-Dean

[Calbullet]

Dean, when you installed the brace, did you also install the Steeda differential bushings they sell?

Mel

[bobcowan]

A while back I was talking to Carl Wade at S&S Automotive, in Denver. He pointed to a big block Superformance. It was there to have a cracked differential case replaced. Again. That was the third one. In his (and my) opinion, the problem with the SPF is that the front mounts are rubber, but the rear is solid. One end is allowed to shift, and the other isn't. Maybe that's why yours cracked????

I have a FFR with IRS. It's the same basic set up as yours. I have a big engine that makes big power, I run it on the track a lot, and I'm not shy about hitting the loud pedal on the street. In short, I beat it pretty hard. No problems with the diff case after 6,000+ miles. During the build, I installed solid alum front bushings.

http://www.vintageperformancemotorcars.com/

I considered the Steeda brace. But the only dramatic case failures I'v seen were in high powered drag cars. I'v not heard of a Cobra having that same catastrophic failure.

[RedBarchetta]

Originally Posted by Calbullet

Dean, when you installed the brace, did you also install the Steeda differential bushings they sell?

Mel

No, just the brace. Note in the pic below that the brace just butts up to the rear bracket. They include a spacer with the brace, but you won't need it on the SPF rear end. Simple swap...unbolt existing bolts and bolt in the brace. Coaxing the thru-bolts on the rear bracket did take some manuevering of the pumpkin to get it all aligned perfectly...it's a very tight fit on my car (those two large bolts, that is).



Here's a shot of another mod that I performed prior. I was having clearance issues with the driver's side half shaft bottoming out on the frame. I'd get grease everywhere and would have to pull the half-shaft to fix the inner CV boot. Someone on SCOF gave me the idea (probably RT) of drilling new holes to effectively "raise" the differential in the frame. I measured carefully (see awe marks still on the bracket) and took it to a neighbor that had access to a machine shop with a drill press. Worked like a charm and ended up providing another 3/8" to 1/2" clearance that I needed.


-Dean

[Lowell W]

Bob,

The rear diff hanger has 3 bolts: two go through the diff cover and the third mounts the hanger to the frame. Isn't there a rubber bushing where the hanger mounts to the frame? I don't recall now without going out and crawling under the car to look. Have you noticed any increase in vibration with the solid front mounts? Any other problems?

Dean,

OK, I get it...thanks. Any problems now that you've changed the pinion angle? Or maybe that mod doesn't change it enough to affect anything?

I really like the idea of the brace, also the solid bushings, if they don't transmit a lot of vibration to the frame.

Thanks,

Lowell

[RedBarchetta]

Originally Posted by Lowell W

Dean, any problems now that you've changed the pinion angle? Or maybe that mod doesn't change it enough to affect anything?

None that I'm aware of. Does this mean that any day now the whole third member is going to go ker-plunk right out from under me?

Seriously, it probably did change the pinion angle slightly, but not enough to cause a binding or out-of-phase condition. In fact, I wonder if I could even perform the second mod (re-drill the rear mounting bracket) if I was running solid bushings at the housing? Less movement to get everything to line-up. Some folks on SCOF have reported better traction and elimination of wheel hop via solid bushings.

BTW, the large third bolt that holds the bracket to the frame does have a large rubber isolator running through it. Otherwise, vibrations from the frame would just shake the hell out of the diff cover connection and probably fatigue the alum cover over time, i.e. crack it.

-Dean

[bobcowan]

Originally Posted by Lowell W

Bob,

Have you noticed any increase in vibration with the solid front mounts? Any other problems?

None at all. If there's any vibration from that, I can't tell. I was swapping axles last week, and the diff seems to be just fine.

[Tinker51]

For those interested, the chore was pretty much exactly as I guessed with one difference.

I released the rear mount from the cover and from the frame and removed it in order to get it out of the way.

I then removed the bolts connecting the driveshaft to the yoke expecting to be able to drop the driveshaft down. Wrong! Problem was I could not get the driveshaft past the bolt in the end of the yoke on the differential. Unfortunately in my car I could not push the driveshaft forward enough to clear it either. Since I had to remove the forward mounting bolts anyway I went there next.

This is where it gets fun. Clearly the rear end is installed in the car before the body is placed on the frame as the nuts for the forward mounting bolts are quite difficult to access. I ended up getting the left one off without too much swearing and as much by luck as anything else. The right one however required my disconnecting the E-brake harness in order to get my fat hands up to the nut. At this point I discovered that the full size 19MM wrench that I was sucessful in using to hold the left nut could not be positioned to grab the right nut. I tried a socket but the bolt is so long that it would not grab. All well and good except a deep socket is too tall to fit in the space. Knowing I din't have a 19MM stuby I went back and tried more with the full size wrench. After about ten minutes of concerted swearing I elected to do what seperates us from the lower primates and make a tool. Since I was not particularly interested in cutting my Snapon in half I went and bought a Craftsman 19MM wrench and another deep socket. My thought was in case the modified wrench did not work I could chuck the socket into the lathe and turn a 1/4 inch or so off of it. I dropped my modified wrench (just cut it in half) in place and it worked so I supported the differential with a floor jack and finished removing the last bolt. Then I slid the differential aft in order to drop the driveshaft out of the way then slid it about two inches forward of it's regular position.

Next I broke out the deadblow hammer and started tapping the rear cover. After a few blows it was loose and I was able to pull it out without difficulty.

The whole thing is now dripping the last of the oil so I can get good clean surfaces for sealing when I re-assemble.
When did people stop using gaskets?

[Lowell W]

Sam,

Wow, what a guy! You really CAN find your nuts with both hands!

Interesting observation regarding the driveshaft. Before I upgraded to forged, permanently greased U-Joints, I was able to R&R the driveshaft with the diff in place. I had the original posi replaced with a Truetrac and changed to 3.27 FMS gears, put the diff back in the car and then was unable to get the driveshaft back in without removing those two front bolts and dropping the front of the diff again. Not sure why...less movement in the U-joints? Slightly longer pinion shaft? Not as deep in the case? Dunno...

You mention removing the nuts from the two front bolts. What # car do you have? My car has the "nuts" as part of a threaded tube on each side which are also braces for the mounting tabs. There's an article or thread somewhere: SCOF or CC, regarding a relatively simple mod for bracing these mounts, but I think you'd at least have to be able to get up in there with a MIG gun, which means dropping the punkin. I had some question or another for Mike Evangelo and he specifically mentioned doing this since I had it out already, but my car came that way.

Also on SCOF is a photo tutorial on installing a drain plug. Not that you'd need the instructions but it's a good idea, especially since you have the cover off.

And yeah, I'm accumulating a box of specially-made tools for my car, too.

Thanks for letting us know what you found out.

Lowell

[Tinker51]

Originally Posted by Lowell W

Sam,

Wow, what a guy! You really CAN find your nuts with both hands!

Anything worth doing is worth doing with gusto!

My car is a 700 series car. I was hoping there was a nut plate or some such thing that the bolts drove into but no such luck. They must have made an engineering change between my car and yours.