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Shepherd - trw swap


Biljol
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I posted this at Irv2 but have not had much luck.

I had done on my 2000 exe 40’

8 new air bags (tag bags were fine)

4 new front shocks

shepperd box replaced with trw from weller

my current issue is a pull to the right

I am also unable to turn the wheel right unless I am rolling forward or backwards. It will turn full right on gravel or grass but not pavement. This was a case even before the box swap I was hopping the box would fix it.

the shop did not fully center the pitman arm I know because I get 2-3/4 turn left and 2-1/4 turn right and they can not get the steering wheel straight.

they said an alinement would fix of course it did not.

The shop now has it back to fix the index of the pitman arm.

any other suggestions on the pull (if not the index)?

and any idea on the unable to turn right?

 

 

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As a resident of Phoenix there are 3 quality shops that I use frequently. Each has it's pros and cons. So in no particular order:

 

Davenport Diesel

Massay's Diesel

Phoenix Laser Alignment 

 

Thanks Ken

 

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Davenport is doing the work although he has decided that after my job is done he is out of the rv business. He got a big commercial client and does not have time for the rv’s any more.

good to hear I have someone that others have recommended.

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3 hours ago, throgmartin said:

I am going to guess that this entire issue will all center on the pittman arm. They HAVE to be indexed. Hopefully Van Williams will respond. He is our resident Roadmaster guru.

Actually, Craig is the master technician regarding TRW swaps and he will answer, either here or iRV2.  His "hands on" experience far exceeds mine.  Craig and I discovered as a team that Sheppard-equipped coaches would require a steering gearbox change, and ALL coaches needed cross-braces and Watts links to cure a design problem in the Roadmaster chassis.  But Chris is correct.  When you say you have more turns of the steering wheel in one direction than the other, two things are probably wrong.  Your Pittman arm is indexed incorrectly, AND you are not operating in the "zero lost motion" position of the steering gearbox.  The Pittman arm has to be indexed correctly--the witness marks on the steering gearbox CASTING and the steering gear OUTPUT shaft have to be aligned BEFORE attaching the Pittman arm.  Next, insure that the wheels are very ACCURATELY pointed dead ahead (use a string stretched horizontally across the front and rear tires, if necessary.  That is what *I* do.  Craig has an eagle-eye and just eyeballs the wheels dead ahead).  AFTER accomplishing these two tasks, the drag link (the double-ended rod that connects the Pittman arm to the wheel spindle) may not align with the Pittman arm.  Adjust it until it connects to the Pittman arm.  DO NOT TURN THE STEERING WHEEL to get the drag link to connect.  DO NOT!! 

In trying to make this more clear, think about this--1) BEFORE you connect the drag link, you have already gotten the steering gearbox to its EXACT center position (the ONLY position in which the lost motion becomes ZERO inside the gearbox).  2) You have gotten your wheels pointed dead ahead. What you are trying to accomplish is to connect the drag link to the wheels without moving EITHER the gearbox output shaft OR moving the wheels.  You get the drag link to connect by LOOSENING AND ADJUSTING BOTH its tie rod end clamps (NOT just one end).  Since the tie rod ends are RH and LH, you have an infinitely fine adjustment.  You WILL be able to adjust the drag link until it connects perfectly without upsetting EITHER wheel dead-ahead position or gearbox centering.  And if you did it PERFECTLY, your steering wheel would be centered.  But it usually is no longer centered, and that annoys most folks, including myself.

SO, you may still need to UNCOUPLE the splined joints that connect the U-joints and shafts connecting the steering wheel to the steering gear.  You can usually do that from inside the coach, after removing the plastic covers that surround the steering shaft. Once uncoupled, you can move the steering wheel however many splines are necessary to get it to be centered when you are driving down a straight highway.  This might take a couple of tries, but it DOES NOT REQUIRE ALIGNMENT!!

This is a difficult point to get across, but replacing a steering gear, a Pittman arm, or even the drag link (connects Pittman arm to wheel spindle) has ABSOLUTELY NOTHING  to do with alignment.

Don't blame otherwise knowledgeable truck mechanics for telling you that you need an alignment after changing the steering gearbox.  They usually swap one component for an identical one--replace a Sheppard box with another identical Sheppard box.  At the end of the procedure, though, they will almost always see the fact that your steering wheel is no longer centered as an indication you need an alignment.  NO.  NO.  NO.  Most of them don't understand the underlying principles and technology...they just repair things, and they are under pressure to replace your Sheppard with a TRW in the "flat-rate" time.  However, you can rest assured that changing a steering gearbox under ANY CONDITIONS does not affect your alignment one iota.

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