Good Shake at Start Out Under Load!

[Dogpatch]

I hitched up yesterday to take my 15,200 loaded 5er in to get winterized. On acceleration from a stop light, I put my foot into the gas pedal and felt a pretty good shake like a drive shaft wobble or something. I let off on the gas and it went away. I tried starting out lighter on the gas peddle at the next few stop lights and it didn't happen. I've noticed this a few times now when I give er the foot from standing start.

Any ideas?

 

[SnoKing]

Pretty standard issue/problem with long bed and two piece drive lines. Issue goes back many years. With a crew LB there is no way around a two piece drive line. Friend has a 2001 Duramax ext cab that did it and GM changed it over from two piece drive line to a single piece aluminum drive line that fixed it.

Axle wrap up effects it under heavy acceleration.

They can shim the center carrier to help with it, however it is a narrow band of adjustment! going to far to fix it loaded will cause the problem when empty. Seems that an air ride rear that is always at the same height might be a solution. SNOKING

#ad

 

[sag2]

Just as Snoking said. It is angle related and if you fix the loader launch shudder it may start to do it unloaded. The best thing to do is just drive it.

 

[Dogpatch]

Mine is a short box crew cab.

Previously when I noticed, I had the truck leveled with the air bags but thought I was riding a bit low on passenger side. This last time I didn't fill the air bags as I was only going a ten minute drive to the RV shop.

Uneven or no air up may be the cause.

 

[gsbrockman]

Uneven or no air up may be the cause.

I take it you're not running a t-fitting to your air bags???

 

[Cummins12V98]

I hitched up yesterday to take my 15,200 loaded 5er in to get winterized. On acceleration from a stop light, I put my foot into the gas pedal and felt a pretty good shake like a drive shaft wobble or something. I let off on the gas and it went away. I tried starting out lighter on the gas peddle at the next few stop lights and it didn't happen. I've noticed this a few times now when I give er the foot from standing start.

Any ideas?

Diagnosis..............3:42's and 68RFE. Try the same with 29K combined, I know! That was with my last combo.

Now with basically the same truck EXCEPT 4:10's and Aisin and 32,500# combined I can hammer it from a stop and have NO shutter, that's where the Aisin shines.

I drove my Son's Longed 3500 SRW Limited towing his 14K dump trailer that weighed EASILY 18K full of PeaGravel. I hammered his from a dead stop and it took off with out even a growl.

So another GREAT reason to own the Aisin.

 

[Dogpatch]

No T- fitting. I asked about that and they said it was smarter to put two valves in, in case one side failed. Although, my back end only drops 1.5" without air bags.

Maybe the T-fitting is a better option?

 

[RustyJC]

No T- fitting. I asked about that and they said it was smarter to put two valves in, in case one side failed. Although, my back end only drops 1.5" without air bags.

Maybe the T-fitting is a better option?

I would certainly think so. If you DID have a failure, why would you want to overload one side and twist the chassis? My system has a tee fitting and one Schrader valve.

Rusty

 

[RaceC]

No T fitting, meaning separate air lines to each air bag is good for truck campers. Due to the high center of gravity, they are prone to tip the truck in corners, so keeping the pressure constant in each bag helps to prevent roll. Otherwise, with a T, the air pressure from one side will go to the other side during cornering.

A fifth wheel trailer puts all the hitch weight in the center of the truck, so is less prone to tip the truck in corners.

 

[Dogpatch]

You'd think with the hitch shop putting a 5th wheel hitch in at the same time, they'd know a t-fitting would've been a better idea/scenario.

 

[DonFitzwater]

Diagnosis..............3:42's and 68RFE. Try the same with 29K combined, I know! That was with my last combo.

Now with basically the same truck EXCEPT 4:10's and Aisin and 32,500# combined I can hammer it from a stop and have NO shutter, that's where the Aisin shines.


I drove my Son's Longed 3500 SRW Limited towing his 14K dump trailer that weighed EASILY 18K full of PeaGravel. I hammered his from a dead stop and it took off with out even a growl.

So another GREAT reason to own the Aisin.

My truck has the 68rfe and 17k on a trailer causes zero launch shudder. The Aisin has nothing to do with launch shudder or not, all driveshaft angles.

 

[Bill Stockard]

No T fitting, meaning separate air lines to each air bag is good for truck campers. Due to the high center of gravity, they are prone to tip the truck in corners, so keeping the pressure constant in each bag helps to prevent roll. Otherwise, with a T, the air pressure from one side will go to the other side during cornering.

Yep, a high center of gravity load could be dangerous with a "T" fitting in the air bag plumbing. When I used air bags when hauling a slide-in truck camper, each bag was plumbed separately. BTW, I removed my air bags years ago and don't miss them.

Bill

 

[Dogpatch]

So what does the auto air leveling come with? T-fitting or separate line to each? Can someone with that system advise?

 

[SnoKing]

My truck has the 68rfe and 17k on a trailer causes zero launch shudder. The Aisin has nothing to do with launch shudder or not, all driveshaft angles.

As I said earlier the rear air system has the rear of the truck always at the same level, and that might be curing the issue for Ron. SNOKING

 

[Tuesdak]

Launch Shudder...

At the end of the day after the angles are all correct you have to replace that squishy soft center bearing mount with poly. Put a camera on the driveshaft and watch it jump 1-2" during Launch Shudder due to the soft rubber around the center bearing. Even a 'low power' hopped up GM 6.2 will do this with a trailer load so it's really not because of all the power but it's damn near impossible to control with throttle application. The downside we noticed is a high speed driveshaft vibration at 75MPH. YMMV.

Your angles change from loaded and unloaded and can cause this issue.

Poly center bearings and more info on angles here:
http://www.iedls.com/Center-Support-Bearings/Pickup-Trucks.asp

 

[Cummins12V98]

As I said earlier the rear air system has the rear of the truck always at the same level, and that might be curing the issue for Ron. SNOKING

I think bit has more to do with the gearing/weight. I was not saying it's the 68RFE at all. If it had the same starting gears and I had 4:10's in last truck I don't think I would have any shudder. If I eased into the throttle it did not happen but if I gave it the juice from the start it was not a happy camper.

Here is a pic with my last combo and current one.

 

[CFulton]

Had that problem with my 2014 2500 lb air suspension 68rfe pulling 13000 5th Dealers did most of the above , shimming, replace entire drive assembly (twice) checked balance and on and on, got lemon lawyer after 1 factory rep said "tell him its normal" dealer left WO open---got another factory rep to look at and 3 days later---pick out you a new truck (1 year later)! That is the short story of the long frustrating journey!
Good luck

 

[Dogpatch]

I've got an appointment with dealer service next Wednesday.

 

[Killgore]

Granted, mine is an older rig, but if we were all standing around, drinking a beer, and discussing this I would have to inject into the conversation that mine developed a shudder and then I started hearing a click, and everybody knows what that is, universals.

- Ed

 

[Dogpatch]

The other thing I brought to the dealer service Mgr's attention is, I deflated my air bags and measured and I'm 1 full inch lower on my right side from the left at the peak of my rear wheel wells.