More on Those Leaking Axle Seals & SU Carburetors

June 1, 2013 | By Staff

IN THE MARCH issue of Auto Restorer John Armstrong wrote an article entitled “Replacing Differential & Axle Seals,” which, in part, includes replacing the RIGHT side axle seal on a 1987 El Camino. Mr. Armstrong could not find any obvious reason for this seal failure and concluded that it was most likely that he distorted the last seal during its installation.

Many years ago I worked as a counterman in an auto parts store and after replacing several RIGHT side axle seals on one of my cars, I started asking every parts store customer who purchased an axle seal, which side axle seal he was replacing. Overwhelmingly, the answer was “the RIGHT side seal.”

Several individuals thought perhaps the reason that the RIGHT side axle seals seemed to fail more often than the left side seals was due to the crown built into most roads—which would tend to move the rear end lubricant toward the right side of the vehicle (at least that would be the case in the United States). I never had the opportunity to find out if in England more left side axle seals failed than right side seals, but I never put too much stock in the “road crown theory.”

Years later, long after I was no longer working in an auto parts store, in a casual conversation with a fellow that I then worked with, Frank (Jim) Karlovsky, who was an engineer and a good gearhead, Jim had an answer for the RIGHT side axle seal leaking question that I think is very reasonable. Jim said that in production the area on the axles where the axle seal rides is machined (not ground) and, depending upon the quality of the machined finish, this area on axles is, to a greater or lesser degree, threaded. On the left side of the car the “threaded area” tends to pull any lubricant in this area inward but on the right side of the car the “threaded area” tends to push any lubricant in this area outward—i.e. causing the RIGHT side seal to leak. Jim said that when working on right side axles one should simply take a piece of fine sandpaper and sand the area where the seal rides, putting a non-directional finish on this area.

Since that conversation I have always followed Jim’s suggestion with good results. But I have never conducted any rigorous scientific testing nor have I made any attempt to quantify the surface finish put on rear axles. And I wonder if perhaps more modern manufacturing techniques have impacted (improved) axle surface finish.

(As you know, marine engines often run in the opposite direction from their automotive “brother” engines and the rear main crankshaft seals on these “counter rotating” marine engines is manufactured differently from the rear main crankshaft seals on the “conventional rotating” automotive engines. This is done simply to prevent leakage at these seals.)

In the same AR article noted above, John Armstrong suggests that seal drivers can be made from PVC tubing and PVC fittings. Again, John Armstrong is “right on.” Two years ago I was replacing the front fork seals on a 1969 Honda CL175 motorcycle. These seals are somewhat buried in the lower fork tubes. I used a 12” piece of 11 ⁄4” schedule 40 PVC tubing along with an end cap and a coupling to make a suitable seal driver. Where John suggested perhaps using a belt sander to massage the PVC pieces as necessary, I used a lathe to obtain the same end result, i.e., a workable tool.

It goes without saying that I enjoy AR and always look forward to John Armstrong’s articles.

Fred Cailey Stockport, Iowa

Those who enjoy John Armstrong’s articles will be pleased to know that he’s currently working on a piece regarding tire balancers for the home shop and is trying his hand with a plasma cutter as well.

We Drive With SU Carburetors Too

Thanks very much for the recent articles on SU carburetors (December 2012 & January 2013). I’ve been playing with SUs since about 1968 when I started owning and maintaining Volvos.

Volvo used SUs and the closely related Strombergs until fuel injection made its way into the product line in the early ’70s. I love these simple, effective carbs. Once they are properly tuned they require almost no maintenance except a bit of oil every so often. If you don’t have the expertise to overhaul a set of SUs there are plenty of professional rebuilders across the country who will do an excellent job for a nominal charge.

By the way, the best tuning instructions I’ve ever seen for the HS6 version are in the Haynes manual for Volvo 122 and 1800 series. I use these steps all the time and can get any good set of SUs to behave.

Roy Olson Tucson, Arizona

Thank you for keeping this magazine open to all old cars both foreign and domestic; I myself do both. As soon as I opened to the SU carb article in the December issue, I recognized the photos of the HS2s because my garage now contains two 1962 Midgets, a 1962 AH Sprite and a 1960 “Bugeye” Sprite. My first LBC (Little British Car) was the worn-out ’62 Sprite bought while still in college back in 1978.

As soon as I got a real job after college, I set about rebuilding the engine to make this little car my daily driver. When I came to the carbs, I found the throttle shafts almost hopelessly worn out but didn’t have the money or time to get the shafts re-bushed. Because of the vacuum leaks coming in around the ends of the shafts, I cut two metal discs and glued them on the carbs over the ends of the shafts after applying a liberal amount of grease to the shafts. The play in the shafts made getting the linkage set for the two carbs a little harder but I then drove the car for years like that.

John Blair Steamboat Springs, Colorado

John expanded on his letter with an article on SU carburetor tuning tips that you’ll find on page 26.