Skip to main content ↑ ↓
Topic: Vibration Isolator Torque Spec (was Motor Mount Torque Spec) (Read 1455 times) previous topic - next topic

Vibration Isolator Torque Spec (was Motor Mount Torque Spec)

While working in the engine today, I notice a circular wear pattern on the motor mount's flat washer.  That seemed unusual for something that shouldn't be rotating so I checked it out and sure enough, one of two bolts on the motor mount was very loose.  I was able to to tighten it to approx. the same feel and the other bolt.

Does anyone know the correct torque spec for these bolts?

Thanks!
Mark Duckworth
2003 U320 4220
Build 6199, Motorcade 17971

Re: Motor Mount Torque Spec

Reply #1 –
Good catch on your visual inspection.
Dan - Full timing since 2009
2003 U320 40' Tag 2 slide

Re: Motor Mount Torque Spec

Reply #2 –
That is a 1/2"x 13 grade 8 bolt dry 110 lbs. lubed 80 lbs.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Motor Mount Torque Spec

Reply #3 –
Mark,those mounts are made by a company called lord isolators,on some of the rubber pieces you can make out a part number.
Not sure but I think those are shoulder bolts where you tighten them until the threads stop.Reseach lord they should have info on
the site.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Motor Mount Torque Spec

Reply #4 –
Those are hard plastic or very hard rubber.  Not sure if they are supposed to be bolt tight. My mounts show signs of movement also . They are supposed to move a little IMHO. 
 The airplane versions have a sleeve to tighten to. These dont seem to.
 I wil check my book wed.

Re: Motor Mount Torque Spec

Reply #5 –
Quote from: Protech Racing –
Those are hard plastic or very hard rubber.  Not sure if they are supposed to be bolt tight. My mounts show signs of movement also . They are supposed to move a little IMHO. 
 The airplane versions have a sleeve to tighten to. These dont seem to.
 I wil check my book wed.
Great point.  The Lord website refers to these as vibration isolators, not motor mounts.  I've attached a drawing of one of their isolators that looks pretty similar to the one in question. Do these wear out and need periodic replacement?  If so do they age out from static load or is it a function of dynamic load, i.e., engine run time?

The Lord 2-piece isolator spec sheet refers one to the "Tightening Torque Chart" but that's not part of the spec sheet.  A quick google search turned up that info here.  Looks like they are specifying standard torque values based on the bolt strength and size.  The torque table is on pp123 of the Lord industrial catalog. 

I'll try calling James at FOT and/or Lord later today and see what I can find out.
Mark Duckworth
2003 U320 4220
Build 6199, Motorcade 17971

Re: Motor Mount Torque Spec

Reply #6 –
Quote from: John44 –
Mark,those mounts are made by a company called lord isolators,on some of the rubber pieces you can make out a part number.
Not sure but I think those are shoulder bolts where you tighten them until the threads stop.Reseach lord they should have info on
the site.
I'll look to see if I can find the part number.
Mark Duckworth
2003 U320 4220
Build 6199, Motorcade 17971

Re: Motor Mount Torque Spec

Reply #7 –
Mark,I wonder if anyone has access to a vibration meter to get a reading on the mounts,we could get a before and after to see
if the new ones really help.From what I can gather the isolators on the side are the same as the rear one.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Motor Mount Torque Spec

Reply #8 –

The bolt torque remains the same on these isolators or mounts what ever you call them. You never leave a bolt loose. The crush will be built into the design. Usually a sleeve.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Motor Mount Torque Spec

Reply #9 –
Quote from: craneman –
The bolt torque remains the same on these isolators or mounts what ever you call them. You never leave a bolt loose. The crush will be built into the design. Usually a sleeve.
Yep, just took it apart and you are spot on (as usual).  There's a substantial steel sleeve in the center.

Lord Series SSB
Part number J-3049-67

If I'm reading the Lord torque chart correctly, it calls for 106 ft lbs dry for the 1/2-13 Grade 8 bolts.

Mark Duckworth
2003 U320 4220
Build 6199, Motorcade 17971

Re: Motor Mount Torque Spec

Reply #10 –
Quote from: John44 –
access to a vibration meter to get a reading on the mounts
I have a vibration meter as an app on my Android phone; it is called Vibrometer.

I have never had a need for it, so I do not know how it works. You might try that.

Trent
Trent and Jean Eyler
2000  U295  4003  WTFE  ISC  350
Build#5603 MC#17385

Re: Motor Mount Torque Spec

Reply #11 –
Quote from: John44 –
Mark,I wonder if anyone has access to a vibration meter to get a reading on the mounts,we could get a before and after to see
if the new ones really help.From what I can gather the isolators on the side are the same as the rear one.
Quote from: John44 –
Mark,I wonder if anyone has access to a vibration meter to get a reading on the mounts,we could get a before and after to see
if the new ones really help.From what I can gather the isolators on the side are the same as the rear one.
After taking them apart, they look fine.  The rubber doesn't appear to be deteriorated from a visual inspection: it's not chalky, checked or brittle.  The rubber portion seems fully bonded to the steel "washer" on each side. I'm going to reinstall, torque both of them and call it good.
Mark Duckworth
2003 U320 4220
Build 6199, Motorcade 17971

Re: Motor Mount Torque Spec

Reply #12 –
On something like that should one use Loctite on threads?
John M
John & Carm Morales

"We travel not to go anywhere, but to just go.  We travel for travel's sake.  Our great desire is to move."

Re: Motor Mount Torque Spec

Reply #13 –
If torqued correctly the bolt stretch will hold the bolt without Loctite. Loctite doesn't harm anything though.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Motor Mount Torque Spec

Reply #14 –
Quote from: John Morales –
On something like that should one use Loctite on threads?
John M
Blue would be OK, not red. Correct torque should do it but that location gets a lot of vibration. Red dust is a tell tale. Red dust around a U joint is really a bad sign.

Pierce

Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Vibration Isolator Torque Spec (was Motor Mount Torque Spec)

Reply #15 –
I reached out to Lord and here's the email conversation.  Their responses are in itaclics:

MD: Good morning. I own a 2003 motorhome that uses your SSB vibration isolators, part number J-3049-67. Do these need to be replaced periodically due simply to age? Mine appear to be in good shape, but they are at least 14 years old. The motorhome has low miles (65,000), so the dynamic loads have been low.

LORD: The J-3049-67 is part of a two piece mount, SSB26-1000-1 that is still in production. In the application they most likely took a set in the elastomer. If there are no visible cracks they should probably be usable. If you are having the unit serviced you might want them replaced in the next couple of years. This mount is available through AstroTex at 972-424-8707.

MD: Thanks for the email.  What does, "took a set in the elastomer", mean?

LORD: Set is defined the amount deformation never recovered after the removal of a load. As an example if these were used to support a 600 lb. radiator the height of the mount would be less than when the mount was installed new. The J-3049-67 had a height of 0.81" new. The height would be less after 14 years of service. There are no guidelines for replacement.

Mark Duckworth
2003 U320 4220
Build 6199, Motorcade 17971