1992 Mack RD688s Steering Gear Drama

[KP2]

The steering gear was leaking by the input shaft.  I was told I could take the top off and replace the seals.  After removing the top I discovered the shaft had a groove in it.  On these forums the only option after finding the groove I saw was to buy another gear.  I tried putting JB Weld in the groove and turning it back down on a lathe, installed new seals.  It held for a few minutes then started leaking again.  Removed shaft again, installed wear sleeve and new seals.  I ran it about two hours and it started leaking again.  I searched for days and could only find one gear through Watts Truck.  Weller would reman one for me but they had to have mine first so that would be a drawn out deal.  So I have ordered the one through Watts.  It was $2500.  I called a few salvage yards and could not find one.  Several places I called wouldn’t even bother to answer the phone or call back after I left a message.

I had considered taking the shaft to a machine shop, have the groove welded up and then turned down but was not sure about the integrity of the shaft after doing that.  Anyone ever done that before?

Is there anyone on these forums with a RD688 that has had this same experience?  If so what did you do?

 

[mowerman]

if the 2500 includes shipping your not going to do much better i found an outfit in florida that sells rebuilt for around 900 plus shipping another 900 depending where you are is it a sheppard or a ross box???

[Vladislav]

Fixing the shaft condition could be the way to go. Lathe work is Ok if you dial the shaft's center well enough before cutting. Grinding in a machine is much better and preferrable option. Welding is no of good options since the shaft is (should be/ could be) made of high carbone steel. Which doesn't weld well and could easily crack through in the welded area later in service. So application of material (metal) on the area could be halvanic (chrome) or ultrasonic metal powder coating. I don't know which kind of technology could be found in your neck of the woods but strongly advise to get off of the idea to weld up.

Also an option might be cutting/grinding the shaft over the worn area to lesser OD. Than locate a seal with lesser ID (and the same mounting size) using a chart or catalog. For example Timken offers a wide range of industrial seals and their catalog is on-line. Not almost correct way of fixing things but could be applied.

[Geoff Weeks]

If it is a Shepard gear, I think the correct repair is to cut the shaft to a smaller OD and shrink a sleeve on where the seal rides. You could possibly have the sleeve made from hard chrome stock, making the repair better than the original. 

These repairs need a qualified machine shop that can do the work. It would take tooling that can cut the hard shaft and sleeve.

I was working on a car that had some brake parts that are NLA anywhere, my machine shop made a repair like the above and was surprisingly reasonable. You just have to think "outside the box" and remember anything made by man can be re-made by man.

 

[KP2]

10 hours ago, mowerman said:

if the 2500 includes shipping your not going to do much better i found an outfit in florida that sells rebuilt for around 900 plus shipping another 900 depending where you are is it a sheppard or a ross box???

I think with shipping both ways, they want the core back(1200 core deposit), it will be about 2700.  It is supposed to be a Sheppard.  The salesman said it was a genuine Mack reman.

[KP2]

8 hours ago, Vladislav said:

Fixing the shaft condition could be the way to go. Lathe work is Ok if you dial the shaft's center well enough before cutting. Grinding in a machine is much better and preferrable option. Welding is no of good options since the shaft is (should be/ could be) made of high carbone steel. Which doesn't weld well and could easily crack through in the welded area later in service. So application of material (metal) on the area could be halvanic (chrome) or ultrasonic metal powder coating. I don't know which kind of technology could be found in your neck of the woods but strongly advise to get off of the idea to weld up.

Also an option might be cutting/grinding the shaft over the worn area to lesser OD. Than locate a seal with lesser ID (and the same mounting size) using a chart or catalog. For example Timken offers a wide range of industrial seals and their catalog is on-line. Not almost correct way of fixing things but could be applied.

Thank you.  I was hesitant to weld then cut down the shaft because I thought it may weaken it.  I thought by putting the wear sleeve over the worn area and a new seal would do the same as cutting shaft down and putting a sleeve but I have no experience doing machine work.  

[KP2]

7 hours ago, Geoff Weeks said:

If it is a Shepard gear, I think the correct repair is to cut the shaft to a smaller OD and shrink a sleeve on where the seal rides. You could possibly have the sleeve made from hard chrome stock, making the repair better than the original. 

These repairs need a qualified machine shop that can do the work. It would take tooling that can cut the hard shaft and sleeve.

I was working on a car that had some brake parts that are NLA anywhere, my machine shop made a repair like the above and was surprisingly reasonable. You just have to think "outside the box" and remember anything made by man can be re-made by man.

 

Thanks.  It is a Shepard gear.  I really don’t know if the machine shop in my area could do it just right.  I know they cut down shafts for tractors but I felt more at ease getting the reman.  I have had other parts made but for some reason my gut said go reman.  

[Vladislav]

6 hours ago, KP2 said:

Thank you.  I was hesitant to weld then cut down the shaft because I thought it may weaken it.  I thought by putting the wear sleeve over the worn area and a new seal would do the same as cutting shaft down and putting a sleeve but I have no experience doing machine work.  

Right machine work presumes sharpness and accuracy with tolerances. Your bad experience with that speedy sleeve is the most prbably due to its imperfect fit. Which could be predicted by its very imperfect shape and even the design. A thin wall tube pressed over unevenly worn surface doesn't seem supplying perfect surface for a seal to seat against and work well. I honestly am surprized at all this technology is count as "good" and so widely used. And at the same time I heard from multiple guys that they use such a sleeve and got leak back again soon.

As less excentricity of the spinning surface is as less deformation of the seal's rubber is required to keep tightness. It's more actual for higher revs applications though so doesn't seem the matter of your issue. Possibly there was leak just between the sleeve and the shaft if you didn't apply sealer or epoxy in between. Or the sleeve's shape was so imperfect so the seal couldn't do its job at all. Or got worn or cut by a certain sharp edge. 

Maybe it's worth for you to just spend a couple of hours in the evening to read on the web basic principles of fabrication of shafts. Engeneering is way not always a rocket since. Most basic points are easy enough to figure just by common logic.

[Geoff Weeks]

With the Shepard box the input seal is a high pressure seal, a speedy sleeve will not work at those pressures, as you found. 

[mowerman]

I still don’t know why the sleeve didn’t work and I was also surprised that you were able to get one