Thunk noise when shifting from forward to reverse

[CapnDirk]

The Itasca Has 98K on her and has only made the 100 mile trip from purchase to home.  It took a couple of shots to get it lined up in the driveway, and recently I turned it around.  What I've experience is what I believe to be a familiar thunk going from forward to reverse of a u-joint.


Anyone know if the P30 with that long drive line was prone to eating u-joints.


I know how to check them, but it's raining for days up here.


Thanks

[LJ-TJ]

Sorry but a 21 foot Dodge Winnebago does the same thing. Not major bad but when you go from park to drive she goes clunk. When you go from drive to revers she goes clunk. Again nothing major. I've check all two universals and in the past changed both universals. Still clunked. I've been told it has something to do with the Lash in the rear end?. I shall be following this thread with great anticipation. Hm? D:oH!

[CapnDirk]

Thanks TJ,  also interested in how the rest of the crowd weighs in.

[jeno]

Mine did that turned out the idol was too high..

[EldoradoBill]

Replaced the 3 joints in my rig, still clunks. Probably in the rear end. No worries...


Bill

[kenwautoone]

Was that the American idol that was high?

[dickcarl]

The Winnebago manual warns against setting false idles.

[CapnDirk]

If you're close to mine you can hear Billy Idol!   


I suppose at 98K It wouldn't hurt to put u-joints in it.  Is it a bugger to get that drive line out?

[EldoradoBill]

Mine was easy; didn't even need to raise the rig, just slid under on a sheet of cardboard. 4 bolts on the rear joint and 2 holding the center bearing to the frame. You will need some sort of press to remove the center bearing from the shaft, or bring the shaft with bearing to a shop and I'm sure they will press the old off and the new on for a couple bucks.

[Rickf1985]

Depends on length, I have three shafts in mine and you have to start at the rear and work towards the front and reinstall in reverse order. Have some jackstands to hold the shafts up while you line things up. And if you take the splines apart be damn sure you get them back together exactly them same way or you will have a hell of a vibration.

[beaverman]

Yep, what Rick said, make sure you put index marks on everything to aid in realignment!

[legomybago]

Not sure where you are geographically, but if you take the entire shaft assembly to a driveline shop, if buy the u-joints and center bearing from them, they will "usually" install and  check balance for no extra charge. If your close to PDX, I can give you a shop name that does this.

[Rickf1985]

That is the best way to go, that way if there is still a vibration it is under warranty if it is the shafts. I have both a clunk and a vibration. Just had the suspect shaft rebuilt. that got rid of the rotational vibration. Now I think it is a bad wheel. The clunk I am positive is the rear sway bar slipping in the bushings at start up when the differential raises up. I have the air suspension so it is a bit different then a full spring setup. The clunk a lot of the time is the spline in the slip joint of the drive shaft binding as you start up. It want to shorten up a hair but it is bound up until you hear it let go with a clunk. Sometimes it is a sign of a dry spline from lack or lubrication and sometimes it is a worn spline. Sometimes there is no logical explanation.

[legomybago]

The clunk I am positive is the rear sway bar slipping in the bushings at start up when the differential raises up.

The Father-Laws 1986 P30 Chassis has this too....At least this is what I think it is. Cant find anything else to blame it on....You can see wear marks on the sway bar bushings from some movement. Normal.

[classicrockfanatic]

Depends on length, I have three shafts in mine and you have to start at the rear and work towards the front and reinstall in reverse order. Have some jackstands to hold the shafts up while you line things up. And if you take the splines apart be damn sure you get them back together exactly them same way or you will have a hell of a vibration.

Not to hijack the thread, Rick, but I had relevant question on your alignment comment. Is it necessary to mark and match the spline alignment, so the drive shaft u-joints will re-align in the same wear pattern? Or is it to prevent mismatched spline wear, and a loose connection?


I took out my drive shaft, and didn't think to mark the position on the splines. I do plan to replace all 3 u-joints, and the carrier bearing before it goes back.
I took photos, and could probably get the alignment back, but if it's only to accommodate joint wear, then I wont sweat it.


Thanks in advance!

[Rickf1985]

The reason is the keep the u-joints in phase. The joint at one end is opposite the joint at the other end. If this is not so then you will get vibration. Some splines have a dead spline, where there is one spline that is not cut out at the end and the mate is not cut on the other end, this makes it easy since they will only go together one way. I saw this on my Winnebago with coarse splines but the Pace arrow with fine spline did not have a blind spline and I had to eyeball it to get it lined up. Eyeballing down a 5 foot driveshaft is not the best way to go but in this case the motor home only has to drive ten miles and it's life ends there so I am not worried about vibration. Do an internet search for  "drive shaft Phasing" and it should tell all you need to know.

[TerryH]

This may help explain. 'Phasing' is well shown towards the end.

http://www.macsmotorcitygarage.com/2014/07/26/video-driveshaft-angle-and-phasing/

[TerryH]

Sometimes there is no logical explanation.

I particularly like that, Rick. Welcome to life.

[CapnDirk]

Lego:


I'm in Vancouver just over the bridge to the no sales tax place ;[) If you know someone that would load the ujoints and bearing for cheap or free, I'm all ears.


Rick:


Thanks for reminding me of the phasing, have not done a multi piece driveline in ages, and was aware of the blind spline which we called the index.  Also, from posts I had not thought of the sway bar, it would make sense since the rear end would want to wrap and unwrap.

[legomybago]

Speaking of indexing, here's my FMC driveshaft. In order to "prevent" vibration, they positioned it one spine off. I put a straight edge in front of it to show reference.

[legomybago]

Capndirk.  Six States Distributors used to do all my driveshafts. They are located on Columbia Blvd not too far from Caterpillar. I haven't been there in ten years since I now live down south

[Rickf1985]

I had Six States build a shaft for my Jeep when Tom Woods was running the place. He now has his own place, http://www.customdriveshafts.com/ . The shaft he built for me was almost 20 years ago and is still in use and I have hammered the hell out of it with a big block for many of those years. And it is a custom double cardan joint shaft which is pretty short. They generally do not last long under high horsepower.
Any driveline shop can do a shaft for a stock RV but if you ever need something custom then Tom is the go to guy.

[Rickf1985]

Speaking of indexing, here's my FMC driveshaft. In order to "prevent" vibration, they positioned it one spine off. I put a straight edge in front of it to show reference.

The rear drive shaft on my M-151 military jeep looks like it was twisted! They built it so that the front and rear u-joints do not line up to compensate for the compound angles in the drive line. The transmission is not centered so the drive shaft is offset to one side a little bit.

[Rickf1985]

Terrry, That is a really neat find and explains the phasing better than I ever could. BUT! Did you notice right from the beginning that the shaft was not properly phased in the beginning of the video? Start and stop it until you get it to a spot where the yoke at one end is perfectly in line in the shot and then look at the other end.

Yep, I am a perfectionist, that is why I was a good mechanic. I spot these things.

[Rickf1985]

Wow, That is NOT how I thought they were laid out. Of coarse I never saw one in person either. I would have thought an angle like that would have had a cardan joint on it. Usually you need two equal angles on either end or a cardan joint on one end with a big angle and a near strait angle on the other end.