weird vibration at speed 60 plus

[y5mgisi]

Here is a pic from a 76 suburban brochure.

[motornut]

[QUOTE=y5mgisi;6278510]I really believe that factory was with the slip at the t-case. But i too have seen it both ways. QUOTE]

I believe factory is front,both of mine are front,my rear most u joint went last year.had some vibration,did both

[75chev4x4]

Originally Posted by Oldriginal86

Don't know how the shaft is presently installed in your truck with a lot of talk about flipping this and that but the shaft appears to be install backwards. The slip yoke end should be at the transfercase and solid end should be at the rear.
Posted via Mobile Device

Sorry I didnt see your post before, u might be right. I could have this thing in backwards. Thank you

[geezer#99]

Looks like bent axle flange!

[y5mgisi]

The axle and hub run true. The drum is the messed up part. Keep in mind this is a full floating axle.

[Ski-me]

Originally Posted by y5mgisi

The axle and hub run true. The drum is the messed up part. Keep in mind this is a full floating axle.

Wow,, that's pretty amazing. I would not of thought that could happen. I thought they were more true than that.......thanks for the video.

Do you think the semi float axles are susceptible too?

[y5mgisi]

I have known of semi float axles, (12 bolt in particular), to have bent axle shafts which would do something similar.

[geezer#99]

I've searched and found some like yours but they could be wrong too. Easy to swap yours around.

[75chev4x4]

Ok, funny thing on my shaft is there is a line scribed where the two joints come together. I might put it back that way and just flip the u joint around and see if that helps.

[Oldriginal86]

Sounds like more than just the trans was replaced. Rear or T-case? Has the driveshaft been pieced together from different trucks?

[75chev4x4]

The rear end is original 14 bolt ff. I was asking myself about the driveshaft too. I dunno if thats what was put in when the turbo 400 was added or how they did it. But a 1310 1350 conversion joint is the only way I could figure 2 make it work. Not taking pictures before I took this thing apart is really biting me in the butt right now.

[Oldriginal86]

Was the truck an automatic from the factory? What T-case do you have now?

[75chev4x4]

Yea turbo 350 from factory with 203, now has turbo 400 with 203.

[lilspike]

You need a 1350 slip yoke and a 1350 replacement yoke for the 14 bolt. End of conversion joints. What you have now is a conversion drive shaft.
Matthew
or vise versa..

[y5mgisi]

You know whats funny, i seem to remember mine being just the other way around. I wanted to try flipping mine around but couldn't for some reason and i think thats why. Now i really wonder! I'll have to climb under there and measure but im almost certain i cant flip mine to the way yours is cause the ujoints are different.

[mrolds88]

One thing I have noticed on this thread is that you have a 203 case and you say you can feel some of the vibration in the steering wheel. You may want to check out the front driveline also. Loose u joints both in the shaft and the front axle and weights on the shaft.

[lilspike]

That is a very good point to check the front as well! Would pay to make sure the T/C mounts are in good condition too. Most are deteriorated and squashed after all these years.

[75chev4x4]

I have the part time kit so my front shaft doesnt spin in 2wd. Its gotta be in this rear driveshaft im sure.

[cedens]

My experience if it shows up over 60 its a tire/wheel issue, i have had that problem a lot with getting the Red Sticky Peanutbutter like mud all over my wheels, its nasty and tough and just spend a $1 at a car wash and clean the insides of the rims, if that still happens any small tire shop can ballance them for you.

That being said on my 06 jimmy i hit a nasty mud hold and got that same red ok clay on the fans which were off .... from then when fans kicked on it was like you broke something.

[75chev4x4]

I ran it without the wheels and tires and still had the vibration. Im thinking its in the aftermarket drum and the driveshaft.

[Keith Seymore]

Originally Posted by 75chev4x4

I ran it without the wheels and tires and still had the vibration. Im thinking its in the aftermarket drum and the driveshaft.

Those drums are huge, so it's not unreasonable to think they could be way out of balance.

When you mentioned checking the shaft with a sharpie marker and it was skipping (only hitting part way around) - that indicates a dimensional problem to me. Either a bent/dented driveshaft or rear axle companion flange runout (bent pinion).

A bent pinion will swing that driveshaft like a jump rope...

K

[75chev4x4]

Yea I could see the ds wobble just a bit. Its tight at the rear diff so I hope its not that. Im thinking it has to be partly that drum that I replaced from the junkyard. I thought it was original gm but it is an aftermarket drum. Im gonna find another original gm drum to replace with.

[y5mgisi]

Any luck?