Possible Rear End Deficiency, late 04's, early 05's

[Wayne R]

I pulled the 2 lower bolts on both sides. There are 5/8 bolts going through a 3/4 hole in the hangers and 5/8 in the frame. The hangers were as far forward as they could go on both sides. there is no sign of movement. The 3/4 and 5/8 holes are round and the bolts are not scored.

I do not see why a 3/4 * 5/8 steel bushing could not be used instead of drilling the frame out to 3/4.

[EngineerMike]

Bushing sounds like an OK idea to me, tho my heart would long for 3/4 bolts. I'm actually surprised WRV didn't do bushings for the frame rails they had in stock w/the undersized holes. Woulda been much better practice than relying on bolts in sloppy holes.

A word of caution- don't reuse the 5/8 bolts you take out. If torqued properly, they may have been stretched.

Here is a look at the bolt pattern from the inside of the PS frame rail on 04 coach 74923:

[Wayne R]

Thanks Mike, I have not decided how I will proceed. I will be in one spot for a while so I have time to procrastinate. I probably will take the holes up to 3/4 using the stepped bushing method you described. I need to take a close look at my front tire wear and alignment of the rear end. I definitely will need to take the rear wheels off. Time to order a torque multiplier so I can remove the rear wheels. I then want to measure the holes in the hanger to make sure I don't need to go oversize they look visually good now.

What is the wisdom of going a 1/16 larger than the bolt. My back ground is in aircraft structure and a shear bolt like this would have a hole size of .7495 -.7505. There also would be no threads in the bearing surface of the hole.

What adjustments are there for squaring the rearend? The oversized bolt holes?

[EngineerMike]

Tolerance in dimension stems from capability to achieve given design requirements from the processes commonly used. The 1/16th oversize allows for irregularities in punching, drilling or hole cutting from hole to hole, plus irregularities in centering of holes, plus irregularities in locating hole patterns vs the overall part. For the Peak chassis, the holes might be undercut for size, then offset from true hole-to-hole dimension by a small amount, then the hole pattern might be offset or rotated from correct position on the part. The 1/16th has been around for a long time. Most holes are not punched these days, but rather laser located by CNC machinery. Some are still punched. But the 1/16th evolved as an amount that would allow for direct assembly most of the time without having to stop production and do hand adjustment to holes to get a bolt in place (or see mooks hammering bolts into place because the holes don't line up fully).

E.g., when I set up the criteria for the steering stiffener kit for 04+ models, I had to consider how the Huck bolt holes and other steel parts were likely to vary across all coaches. The frame & OEM bracket holes for the rear OEM steering gear flange bolts are oversized by, IIRC 1/16th. And the pattern in the OEM bracket might vary a bit from the pattern in the frame. And after welding, the OEM front vs rear bolt holes are likely to have shifted some amount due to weld shrinkage and warping of the assembly. Same could be true to some extent of the Neway flange pattern vs the frame pattern. In the end the 1/16th is more about the larger world variations than the bolts vs. bolt holes, for which a tighter spec could be maintained assuming the holes all wind up in perfect alignment. For the first set of steering kits (which were fab'ed by hand and holes punched), I allowed 1/32" extra space (above other tolerances I considered necessary, for a total of 1/16th void assumed) between rear OEM bracket face & center of huck bolt holes, just to be sure the kit would fit without substantial filing of holes. The current version is laser cut of cold rolled flat sheet steel and I removed the 1/32 slop as hole location should be controlled to about 0.003" or less variation from edge of part. But I left the other 1/32" for fold vs bolt centerline as the bending is less precise than hole location. In theory the frame channel holes have this bend tolerance issue up/down vs flanges.

I make the assumption that if the Neway flange gets centered with its bolt pattern vs. the frame pattern, that all holes will line up neatly and the rear end be in alignment vs. the front. In an ISO 900x environ, that would work, as the frame would have been assembled using a jig that is trued to laser precision. I'm just guessing when I assume WRV didn't have such a jig, and relied on high level of accuracy in supplied parts, with some latitude to adjust where/as needed.

W/all that said, I don't know what the criticality of the rear vs. front alignment really is. Obviously if your rear end shifts enough, you can get some bad results. If it is fixed in place but 1/4" out of square w/the coach centerline, to me that would mean an angle of .25" divided by 96" (approx for out to out of tires) or ~1/7 of a degree per 1/4" (i.e. 1.5" off square, an egregious amount) is ~6/7 degree which would require the sort of constant steering pressure Louis talked about above. Down around 1/8 or 1/4" my suspicion is you wouldn't see much drivability problem but might see tire wear issues over a lot of miles, but that's only a guess. As square as possible would obviously be best.

As to replacement bolts, yes, bolts with smooth shank in the connection part would be better than threads in the sear plane. Assume 1/4" for the tower and 1/4 for the frame, that's 1/2" steel. You won't likely find a flange bolt w/a 1/2" smooth shank. Add two 1/8" oversized washers and you have 3/4" smooth, and probably the first graduation is 1". So this may be a case where the standard bolts available are not ideally suited. You could add washers to make it so.

As to torque, IIWMI'd tread it like a slip critical joint and torque to achieve pre-tension in bolt to eliminate slip and obviate issues of threads and bolts in shear. Not sure what that value is for 3/4 Grade 8, probably around 250-300 ft-lb.

[Wayne R]

Good explanation. Since I am not worried about Assembly line issues, I will drill or ream mine to .750 depending on weather the hanger holes are actually still round.

[JohnLori]

We have the rig with serial #75320, mentioned by EngineerMike in post #6 above. We were lucky enough to be at Mike's for a steering bracket repair when he noticed we had the 5/8" bolts in the hangers.

So after we left Auburn, we stopped at Henderson's Line-Up in Grants Pass and had those rear suspension connector bolts changed. This was the first Alpine that Henderson's has done this to, and it took them about 3.5 hours of work, although we were there all day because they were kindly squeezing us into their busy work schedule.

They replaced each bolt one at a time, as it appeared that the holes were still lined up. When they were done, a thrust angle check was within specs, so the rear end had not moved. Bottom line: $500 for labor, $75 for the bolts and nuts. $192 for the alignment check (front was ok too). A full 4 wheel alignment would have been $375 rather than the $192.

Gilbert, the service manager at Henderson's, was very nice and efficient and the techs there knowledgeable. I would definitely recommend them.

It's nice to avert another possible problem, and great to see those hefty 3/4" bolts in there now.

[Wayne R]

Johm, Good news , I don't believe mine has moved either.

[zinom]

I finally got around to checking my bolts on #75323. MY bolt pattern looked more like the sketch from Alpine (Post#19) than EMikes photo (post #30). A 1&1/8" socket seemed to fit the heads and nuts a little sloppy but a 1&1/16 was too small. Then; why not do the correct thing? I got out the calipers; and sure enought the bolt was 0.75" aka 3/4". It looks like coach length may be a factor SOMETIMES, and s/n may be a factor SOMETIMES. Well I hope I've done my part to confuse the issue; good-luck. Matt

[EngineerMike]

Matt-This is purely a guess, but that looks like good news for the upper end of the range (highest confirmed chassis number w/the problem is 75330). My theory as to why this is good- if they had frame sets ordered which entered production as Matt's 75323 that had correct holes ordered, then the supply of 5/8 holed frames likely ran out fairly quickly. Perhaps they had a run on 36 footers and had to reorder but got the correct holes spec'd, while still working from a stock of 40 footer frames, maybe...

IIWMI'd still check if my rig was an 04 or 05. Easy to do and simple peace of mind.

[dshogman]

s/n #75294 checking in. New bolts installed today at Henderson's in Grants Pass. No prior movement noted by tech before he started, and he did one at a time - with a time out halfway through to get a new drill bit - so nothing moved during the process. I have that warm - and emptier pocket - feeling that another disaster may have been avoided down the road.

[Wil Rathke]

I checked the rear end mounting bolts today on our coach and a 1-1/8" socket fits just right on the bolt heads. S/N 75375 and the "window sticker" has a date of 01/05/05 on it. I have not noticed any unusual handling problem.

[Jim&MaryJo]

Checking in with Coach#74956 (04 FDDS).
I have horizontal rows with 5/8ths bolts.

Guess I dodged that one...

[two sailors]

FWIW #75325 has the correct attachment. 1 1/8" nuts.

[Wildman Bill]

My 04 MDTS #75092 has the two row, 6 bolt horizontal bolt pattern. Guess I squeeked by. Bill Hall