speed related Vibration (approx 55-75) seeking opinions

[Oldsnut]

Hey guys, I hope ths is the t place to post this, even though it is not a modification. I have an 87 R10 Suburban 2wd, 350ci, 4 speed auto, 219K miles. Have had this vibration for a while (years) and finally attacked it last night thinking it might be u-joints. Drive shaft is two piece with a center carrier bearing. Took rear shaft out last night and realized that I could run the engine/trans/ front shaft and carrier bearing up to speed to see if there was any signs of vibration. Sure enough I could feel the vibration on the center carrier bearing support/cross-member. Feeling the rear of the transmission felt pretty smooth, nothing like the cross-member. I replaced the front u-joint and it was still there. I removed u-joint and flipped over the yoke and reinstalled u-joint and the vibration was still there and my helper thought it was worse, so I flipped the yoke back over. The center carrier bearing feels ok, by hand, but of course I cant spin it as fast as I need to get the vibration in my hands. I am guessing it could be acting like an antenna and vibration could be coming from trans, but I will go ahead and get a new carrier bearing, but that will take several days to get. Just wondering if any of you have seem this, or have any other ideas.
Thanks for any input,
Allen

 

[1987 GMC Jimmy]

I’d check for steering and suspension play (tie rods, idler/Pitman arms, wheel bearings, ball joints). That may clue you in on something. What about tire balance?

 

[Oldsnut]

Apparently you didn't read the part where I said "Took rear shaft out last night and realized that I could run the engine/trans/ front shaft and carrierbearing up to speed to see if there was any signs of vibration. Sure enough I could feel the vibration on the center carrier bearing support/cross-member."

 

[1987 GMC Jimmy]

I looked at this in a hurry and missed that part. I understand that you’re trying to fix your issue, and you want people to pay attention to the specifics of your problem so that’s 110% my fault, but that came off as pretty ******, and there’s no need for all that.

 

[Oldsnut]

Yes, I guess it did. Sorry didn't mean to offend.

 

[theblindchicken]

I'd check the condition of your trans mounts before you tear into it. If you can't remember the last time they were replaced, I'd say it's time to get a new set of em.

 

[78C10BigTen]

I just had a similar issue where the bolts that hold the mount to the trans fell out and the trans was waggin side to side under there. Scary was i had not known and did over 100 miles on the highway like that.

 

[Oldsnut]

Thanks for the input. Rear Trans mount looks, feels fine. I am currently waiting for the new carrier bearing, but now another question, Is there a specific procedure for aligning a carrier bearing? There is enough slop in the holes that if you were really careless you could get it torqued or have some binding and not even realize it. Does anyone know of a special procedure for installation?

 

[da_raabi]

Thanks for the input. Rear Trans mount looks, feels fine. I am currently waiting for the new carrier bearing, but now another question, Is there a specific procedure for aligning a carrier bearing? There is enough slop in the holes that if you were really careless you could get it torqued or have some binding and not even realize it. Does anyone know of a special procedure for installation?

I'd like to know this too. I have a similar vibration and had the shaft rebuilt with new u-joints and carrier. When I went to re-install I did wonder about those slots. Maybe @chengny has something up his sleeve? He always seems to have those hard-to-find procedures...

 

[Snoots]

I'd run a snap-line from the center of the tranny shaft to the center of the rear axle yoke.

But that's just me.

 

[Oldsnut]

New carrier bearing arrived and I pressed it on. There seems to be so little alignment error that can be made and with the big rubber mount that the carrier bearing sets in that I am assuming the bearing becomes self-aligning. I installed the half shaft with new carrier bearing last night and the vibration is still there. I am back to thinking the source of vibration is the transmission and the shaft and carrier support are acting like a speaker or something. Not sure what to think. Might have to go on living with it.

 

[da_raabi]

New carrier bearing arrived and I pressed it on. There seems to be so little alignment error that can be made and with the big rubber mount that the carrier bearing sets in that I am assuming the bearing becomes self-aligning. I installed the half shaft with new carrier bearing last night and the vibration is still there. I am back to thinking the source of vibration is the transmission and the shaft and carrier support are acting like a speaker or something. Not sure what to think. Might have to go on living with it.

Yup, you pretty much summed up right where I am at. Its a doozie for sure. My only other thought was maaaaaybe the harmonic balancer is dying.

My vibration feels like a buzzing. I get up to 45 and I get vibration, it stops through 60 or so, then 65 and I get a buzzzzz..... buzzzzz.....buzzzzz. Its not continuous, it pulses like that. Looonnnggg annddd sloooowwww. The faster I go the worse it gets. 75+ is... out of the question.

Worst part is I have no idea how to troubleshoot it without simply replacing parts.

 

[shiftpro]

Sounds very much like my issue as well. It's on my '81 crew cab and hots around 55mph. If I have load in the bed or when towing enough on the trailer to get some tongue weight then it stops. Truck has 177,000 kilometers. Guy I bought it from told me about it so it's been doing a while. Once I get up to 60 mph it smooths out, but also at 60 mph my truck is spinning over 3000 rpms.
TH400, 454.

 

[Rusty Nail]

Yup, you pretty much summed up right where I am at. Its a doozie for sure. My only other thought was maaaaaybe the harmonic balancer is dying.

My vibration feels like a buzzing. I get up to 45 and I get vibration, it stops through 60 or so, then 65 and I get a buzzzzz..... buzzzzz.....buzzzzz. Its not continuous, it pulses like that. Looonnnggg annddd sloooowwww. The faster I go the worse it gets. 75+ is... out of the question.

Worst part is I have no idea how to troubleshoot it without simply replacing parts.

I didn't realize you didn't get yours fixed.
Now there are TWO OF YOU with the same trouble?

 

[da_raabi]

I didn't realize you didn't get yours fixed.
Now there are TWO OF YOU with the same trouble?

Yeah I've still got this issue. Experience it every day back/forth to work. Never really changes. I've had 101 other projects on my hands (see my TH350 thread) so this has been a lower priority.

@shiftpro I've got the same setup. 454/TH400 with 4:10 gears, so at 70mph that old drivetrain sure is singing!

I really do hope I can get this figured out one of these days. One weekend I just need to tackle it and really dig into everything. Suspension/bearings/drivetrain/etc.

I have not tried (nor even thought of) the idea of removing the rear d/s and running it up to "70". That's a good way to rule out tires/suspension/wheel bearings/rear diff etc. I'll start there because its easy and see what happens.