replacing rear end

tom freiberger · #1 (**permalink**) 10-29-2007, 06:35 AM

Just wanted to ask. I'm replacing the rear end in my 74 Spider and is it reasonable to remove the diff alone without pulling the whole axle or should I remove the whole assembly.

**ronsbackyard** · #2 (**permalink**) 10-29-2007, 08:57 AM

are you just replacing the ring and pinion?.............its going to be easer to work on if the diff is on a bench..............i would'nt want to try that while still on the car.Unbolt the trailing arms,flex brake pipe,top shock bolts and trunion from the the diff. Have the body supported at the rear jacking points and slowly lower the diff.It goes without saying...........Use all the safety practices we all talk about in here

tom freiberger · #3 (**permalink**) 10-29-2007, 10:13 AM

Thanks, that was my original plan. Then I starting wondering if there might be a better/easier way. Never hurts to ask.

Alfajay · #4 (**permalink**) 10-29-2007, 09:16 PM

Tom:

Digging into the internals of differentials may be more complex than you realize. Why are you replacing your diff? Old one making noise? Want to switch from a 4.56 to a 4.10?

You can't just unbolt the old ring & pinion, install a different one, and be on your way. As ronsbackyard wrote, even if you could, it would be infinitely simpler to do it on the bench. Look at your rear axle assembly - the only way to get inside it is to unbolt the two steel tubes from the aluminum center section, and you couldn't possibly separate the tubes with things still mounted to the car.

But beyond that problem, there is the issue of setting up the R&P. Read that section of your Alfa repair manual. There are many measurements that have to be taken, many shims that have to be inserted/deleted in order to get the correct relationship between the R and the P. Practically speaking, it is an impossible job for a home mechanic (we don't have the measuring tools or a supply of shims), and a prohibitively expensive one to pay a pro to do unless you are building a race car or restoring an 8C2600 (it just takes too many hours). Swapping a complete rear end assembly IS something that you can do in your driveway.

tom freiberger · #5 (**permalink**) 10-30-2007, 05:00 AM

Jay, Yes I am planning to go from a 4:56 to a 4:10, plus I had a lot of play in my current R&P. Since I already replaced bearings and seals on my existing axle, I was planning on using my axles and axle tubes with my newer used center diff. I was not going to mess with the R&P, just bolt my old tubes to it. Does this makes sense to you?

GTD · #6 (**permalink**) 10-30-2007, 07:13 AM

Tom
It would be more advantageous to swap your new bearings (and buy new seals) to the 4:10 axle. As Jay stated, setting up the internals of a rear diff is not a job for the weekend mechanic.

**Bill S** · #7 (**permalink**) 10-30-2007, 07:55 AM

My knowledge of Alfa rear ends is somewhat limited since all I've ever done is swap them out. Is it true that you can mess up the ring & pinion settings by removing the axle and tube from the set up side?

tom freiberger · #8 (**permalink**) 10-30-2007, 08:09 AM

So, Best thing to do is to leave tubes attaches to center diff, install new outer seals, and then just swap the axles and bearings.

Alfajay · #9 (**permalink**) 10-30-2007, 09:50 AM

tom freiberger had written: "Since I already replaced bearings and seals on my existing axle, I was planning on using my axles and axle tubes with my newer used center diff. I was not going to mess with the R&P, just bolt my old tubes to it. Does this makes sense to you?"

No, but we're getting close. The left hand axle tube (the one with the large flange) and the aluminum center section, must be kept together as a pair. The side-to-side play of the differential is determined by BOTH of these parts, and there are large enough manufacturing tolerances that you can't substitute the left flange from your old 4.56 diff onto your new 4.10 diff and be sure that the play won't be too loose/tight. The factory placed shims behind the bearing races to compensate for these tolerances. Removing and replacing axle tubes from the SAME assembly is OK - you just can't intermix them.

Tom then went on to write: "So, Best thing to do is to leave tubes attaches to center diff, install new outer seals, and then just swap the axles and bearings."

Yes, that I will agree with. Axles are definitely interchangable

tom freiberger · #10 (**permalink**) 10-30-2007, 10:16 AM

Glad I asked this question first before diving in. Thanks to all for all the imput. Saved me from making a major mistake.

Paradiso · #11 (**permalink**) 10-30-2007, 05:17 PM

Tom:
Do you already have a 4.10 rear? I have one I was going to swap into the 71 TS, most likely ain't gonna happen. Let me know if you need it.

John