Experts Only - Desperate Plea for Help - FJ40 Driveline Vibration. LONG Post. (1 Viewer)
- Thread starter nazdackster
- Start date
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"Drop the nose of the diff" ??? Not If you have a Double cardin you raize the nose - about 25mm (1") that gives a Idea of just how much without debating on Degree's. With DC joint the diff Flange should be pointing directly at the gearbox out put flange
- 1 deg. (for the load take up).
- 1 deg. (for the load take up).
- Thread starter
- #43
It's not that I don't want to try it. It's that I'm short on time and I was looking for more of an engineering opinion rather than trial and error. In my estimation, an extended shackle alone causes a 5° difference, we have evidence of a 7° problem, other sources that say the difference should be within 1°, but others that say 3° might still work. And with the diff tipping up under load, that means I'm starting with an 8° issue here.
On the other hand, the operating angle of one end is only 9.6 while the other is 2.4. If I use a larger shim, they both increase a lot, which will definitely make it happy for equal angles, not happy for larger operating angles and less life. So I guess what we're saying is that it's better to have smaller drive angles, but unequal is more OK than larger drive angles. Logically, that's where a 2° shim is. I really don't want it borderline either. So if I seem reluctant to try a small increment first, that's why. If I had a good explanation of why a small increment is best, I would be more inclined to try it. If I can't get the shims made today, I'll stuff something small in there and try it tonight.
Since I have to take it to a spring shop anyway for parts, I'll probably just take my best estimate and run with it. A 5 degree gets me to near a 3° difference under load but also minimizes drive angles. That's my best guess at this point (and cancels the effect of an extended shackle)
That's the logical discussion I was looking for from someone else. Is it better to nail the operating angle difference dead nuts and have larger operating angles, or just get it close and have slightly smaller but different operating angles? Sorry if I seem like I'm overanalyzing this, it's my nature. There is something to be said for just trying something smaller though I guess. If it takes care of it, who cares? I just want my first shot to work.
I'll write back once I get something in there. Thanks again!
Southeast Overland
Get lost! Go explore!
Naz - I'll be driving up for the UPO 2010 trip from SC, through TN, IL, WI and into western MI if you want to caravan in case any problems pop up. If you do, email me at Steve a t SoutheastOverland ditty com.
Didn't mean to push you.
I just think that, in theory, there are two options to solve your problem.
But first you must be sure the angle is the problem, I haven't seen a post wich confirms that it is.
If you don't try there will be no time to solve the problem if it is not the angle.
I just think that, in theory, there are two options to solve your problem.
But first you must be sure the angle is the problem, I haven't seen a post wich confirms that it is.
If you don't try there will be no time to solve the problem if it is not the angle.
- Thread starter
- #46
Thanks Steve! We have to leave Thursday night for Washington Island for a wedding, will get to UPO by Tuesday, traveling between. Thanks for the offer though... See you there.
SHIMS!
Michael - should know something very shortly. Spring shop couldn't do it today, but I bought the U-bolts & pins. Should know it a couple of hours, if that long. I hope this works! What's the other option?. Time to go drive 75 once I get these on...
My eyeball says those are what, 5-7deg?
- Thread starter
- #48
IT WORKED!
SUCCESS!!!
The vibration is totally GONE!!!
I put 6° shims in it, which gets me pretty close to parallel. It still looks just shy of parallel.
The bad news is, after I got off the highway, it started stumbling really bad at idle. That's happened before, probably EGR stuck open. I think this vehicle is trying to tell me something. It will have to come up with something better than that!
Anyway, THANK YOU AGAIN to all who contributed. Friday when I wrote this , I was really at my wits end, and feeling totally lost about what direction to take next, and suspecting that I just spent a ton of hours putting in a junk transfer case, and all the other fixes and upgrades I just finished were a waste of time. I probably wouldn't have even mentioned the angles had I not let someone else drive it who noticed the angles were off some, but probably didn't matter. WRONG!
You guys nailed it!
I'm glad I went for the near-full correction option, it's never driven smoother since I've owned it. I talked it over with a car guy at work this morning and showed him the angles, and he thought for sure this would fix it. He wasn't worried about 15° operating angles as long as they were the same. They'll be less on trips since it's loaded down anyway. We agreed to shoot for the full correction, less a little bit. He thought diff windup would be minimal on the highway and wouldn't matter off-road, so we targeted just shy of the 7.3°, and settled on 6° since that's 1/2" thick at one end, material we had. The 3rd gear "wind up" / shudder / rumble is gone too. I only got it up to 57 on that little stretch of highway and I would say 98% of the vibration is gone. Close enough!
The wedge in position...
The finished angles... Nice!
Now I'm off to find my idle problem. Maybe all that vibration was making the EGR valve close easier! Better here than on the trail. Last time I got it off the jack stands, the starter quit not long after, so I did the FJ60 upgrade. Well worth the trouble. Edit: Idle was EGR or brake check valve. Cycled both and it's gone.
THANK YOU, THANK YOU, THANK YOU!!!
You got me back on track.
PS... If you're doing this and the new U-bolts are a little over-bent like mine were, you can whack them really hard on another bolt hitting the outside of the radius, they'll open up a little.
SUCCESS!!!
The vibration is totally GONE!!!
I put 6° shims in it, which gets me pretty close to parallel. It still looks just shy of parallel.
The bad news is, after I got off the highway, it started stumbling really bad at idle. That's happened before, probably EGR stuck open. I think this vehicle is trying to tell me something. It will have to come up with something better than that!
Anyway, THANK YOU AGAIN to all who contributed. Friday when I wrote this , I was really at my wits end, and feeling totally lost about what direction to take next, and suspecting that I just spent a ton of hours putting in a junk transfer case, and all the other fixes and upgrades I just finished were a waste of time. I probably wouldn't have even mentioned the angles had I not let someone else drive it who noticed the angles were off some, but probably didn't matter. WRONG!
You guys nailed it!
I'm glad I went for the near-full correction option, it's never driven smoother since I've owned it. I talked it over with a car guy at work this morning and showed him the angles, and he thought for sure this would fix it. He wasn't worried about 15° operating angles as long as they were the same. They'll be less on trips since it's loaded down anyway. We agreed to shoot for the full correction, less a little bit. He thought diff windup would be minimal on the highway and wouldn't matter off-road, so we targeted just shy of the 7.3°, and settled on 6° since that's 1/2" thick at one end, material we had. The 3rd gear "wind up" / shudder / rumble is gone too. I only got it up to 57 on that little stretch of highway and I would say 98% of the vibration is gone. Close enough!
The wedge in position...
The finished angles... Nice!
Now I'm off to find my idle problem. Maybe all that vibration was making the EGR valve close easier! Better here than on the trail. Last time I got it off the jack stands, the starter quit not long after, so I did the FJ60 upgrade. Well worth the trouble. Edit: Idle was EGR or brake check valve. Cycled both and it's gone.
THANK YOU, THANK YOU, THANK YOU!!!
You got me back on track.
PS... If you're doing this and the new U-bolts are a little over-bent like mine were, you can whack them really hard on another bolt hitting the outside of the radius, they'll open up a little.
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Great to see it works, if you reverse the driveshaft and put a DC on the top end. You can then put your shims on the other side to flip the diff up. This will reduce the drive shaft angles and the risk of faillure.
Have a nice trip and let us know how it was.
Have a nice trip and let us know how it was.
This is just a comment on shaft angles and how things can be different from one vehicle to another.
My '83 has a SOA and it still has the OME springs on it from before the modification. (This was done by one or more of the PO's). The axles are both turned but not enough to compensate for the lift springs, you can see by eyeball that the pinions are pointed below the TC. The rear shaft has a DC joint at the TC end, the front shaft I don't know but I think it must have also.
At highway speeds there is a slight but tolerable vibration from the front shaft if I leave the hubs engaged, there is no vibration from the rear shaft.
This truck appears to have 4" lift OME's since it is 10" taller than my '79 which still has about 1" to 1 1/2" lift left from the 3" rearch with added leaves that was done about 30 years ago. How come I don't have a vibration problem when common sense and other's experience says it should shake my teeth out? Mind you, I am not complaining.
My '83 has a SOA and it still has the OME springs on it from before the modification. (This was done by one or more of the PO's). The axles are both turned but not enough to compensate for the lift springs, you can see by eyeball that the pinions are pointed below the TC. The rear shaft has a DC joint at the TC end, the front shaft I don't know but I think it must have also.
At highway speeds there is a slight but tolerable vibration from the front shaft if I leave the hubs engaged, there is no vibration from the rear shaft.
This truck appears to have 4" lift OME's since it is 10" taller than my '79 which still has about 1" to 1 1/2" lift left from the 3" rearch with added leaves that was done about 30 years ago. How come I don't have a vibration problem when common sense and other's experience says it should shake my teeth out? Mind you, I am not complaining.
The universal joints create an inbalance when rotating under angle(every turn has a fast and a slow part), so when you use 2 opposite in a driveshaft they will eliminate each others inbalance if they are counteracting. If they have different angles they are not compensating each others inbalance which gives vibration. When you increase the angles (lift/SOA) there will be more inbalance that needs compensating which makes the drivetrain more sensitive to vibrations. When you use a DC the diff can be angled to the TC so the angle is reduced to almost 0, this is possible because the DC has 2 universal joints that compensate each others inbalance and have only half the angle to overtake (other half is eliminated by angling diff up to TC)
Hope this clears up some questions.
If someone has comments or additions please do.
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- Thread starter
- #52
You can check the angles on the front and correct if needed, but it will also change your caster if you change it. Probably wouldn't hurt to measure the back too and see how close it is pointing to the TC joint. You might be surprised. I thought mine was OK before I did all the other things that made my vibration severe. It clearly was not since it's way smoother now that it has ever been. It only took a couple of hours to add wedges (with air tools), maybe less.
From what I've read, be sure to overfill the diffs if you have the shafts pointing way up in the air, to make sure the bearings get some lube.
Supposedly 1 degree is the limit (per Dana/Spicer) but some folks say you can get away with 3°. I can testify for sure that 7° is way too much. I'd bet that's true with a DC too. I must have been beating the gears to death with that vibration. It also introduced other weird dynamics in the system. A wiggling in 2nd, A surging / winding up / pulsation in 3rd, a "hard spot" in 4th that I had to power through, then it felt free to accelerate again. I was using A LOT of power just to get past the vibration zone. That can't be good. I wonder where all that energy was going. It had to be heating something! I am SO GLAD to have gotten to the bottom of this. It rides SO much better.
Bear Lake Cruiser
SILVER Star
I have the exact same problem ss original poster but my transfer output flange and rear pinion flange are almost exactly parallel. So spring shims likely no help. Brand new drive shaft mounted in phase. Runs smooth when I pull the shaft and run on front wheel drive only. Stake nuts tight. I'm leaning toward rear transfer output bearing or pinion bearing. Thoughts?
Are you sure the DS is balanced?
Bear Lake Cruiser
SILVER Star
Pretty sure. The guy who built it here in Tucson said he had the only machine in the city that spins them and balances on both rotational directions. But maybe that was BS. The symptoms are the same with the old shaft and new. I just got back from the tire shop and had them all balanced on the very outside chance that is what is causing it but no go on that.
Vibration and rumble definitely increase with drive line speed not engine RPM. Georg took a brief look at it when passing thru town but it was pitch dark out. He was of the opinion that it may need a thicker thrust washer/shim on the back of the xfer. I have yet to put it in though, or even figured out how to do it. He sent me a shim kit. All of this was back in spring but I parked the cruiser for the summer as I went north for the warm months. Now I am back and it is time to fix it. I need to put it up on jack stands and run it up to speed. I did this last spring but I had no help and had to block the throttle while I took a look. I was too scared to climb underneath for a close look without help. Gotta get close to see where the rumble is coming from. Difficult to track this kind of noise as they tend to telegraph throughout the driveline and into the tub.
I have not changed suspension geometry or shocks on this thing at all since I acquired it back in 2009. And the noise got noticeable after a really tough day wheeling last spring. Lots of stream crossings and rock crawling that day and almost rolled it once. In fact, I never heard it before that trip. I have two new front motor mounts and yet to get the cross member mount. I'm thinking I may have popped one that day. I can feel the vibration and see it in the steering but it definitely coming from rear driveline as it runs smooth as silk when running on the front shaft only with rear shaft removed.
Vibration and rumble definitely increase with drive line speed not engine RPM. Georg took a brief look at it when passing thru town but it was pitch dark out. He was of the opinion that it may need a thicker thrust washer/shim on the back of the xfer. I have yet to put it in though, or even figured out how to do it. He sent me a shim kit. All of this was back in spring but I parked the cruiser for the summer as I went north for the warm months. Now I am back and it is time to fix it. I need to put it up on jack stands and run it up to speed. I did this last spring but I had no help and had to block the throttle while I took a look. I was too scared to climb underneath for a close look without help. Gotta get close to see where the rumble is coming from. Difficult to track this kind of noise as they tend to telegraph throughout the driveline and into the tub.
I have not changed suspension geometry or shocks on this thing at all since I acquired it back in 2009. And the noise got noticeable after a really tough day wheeling last spring. Lots of stream crossings and rock crawling that day and almost rolled it once. In fact, I never heard it before that trip. I have two new front motor mounts and yet to get the cross member mount. I'm thinking I may have popped one that day. I can feel the vibration and see it in the steering but it definitely coming from rear driveline as it runs smooth as silk when running on the front shaft only with rear shaft removed.
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Bear Lake Cruiser
SILVER Star
Oh, and all fluids full clean and pure. Got no chunks or even sludge when I drained it and inspected the magnetic plugs. (tranny, transfer, rear diff.)
When you pop a motor mount it's almost always the driver side. Easy way to tell is put it in low range and pop the throttle. Your shift lever
will tilt excessively to the passenger side and you'll probably hear the fan contact the shroud. Once I went to an Aussie 5speed in the 60
I had to carry a spare all the time. Every other outing on a rough trail I'd lose one. Finally I just drilled through the mount and used a long 7/16 bolt and locknut. Even if the rubber tore, the engine couldn't lift and trash the shroud. Drag racers traditionally used a chain bolted from the block to frame as a safety measure.
will tilt excessively to the passenger side and you'll probably hear the fan contact the shroud. Once I went to an Aussie 5speed in the 60
I had to carry a spare all the time. Every other outing on a rough trail I'd lose one. Finally I just drilled through the mount and used a long 7/16 bolt and locknut. Even if the rubber tore, the engine couldn't lift and trash the shroud. Drag racers traditionally used a chain bolted from the block to frame as a safety measure.
Bear Lake Cruiser
SILVER Star
Yeah Dave, I have replaced them all on my 60. I haven't heard it hit the shroud on this 40 and the shifter seems fine around town but I noticed the day of the big wheeling trip the shifter was moving around a ton but no contact. It is fine running around town. I will romp on it in the driveway like you say tomorrow. I'm going to change them all out but I am discounting this as the cause of the vibration. If I could actually find a smooth road in Tucson I could hear better what is going on. The streets in this town are cratered like North Vietnam after Linebacker II. Sheesh. I might come pay you a visit to get your spin on it before I start shot gunning parts. Interested in your front bumper for the 40 series.
I don't know if a bent axle housing or inner axle would run relatively smooth without the DS connected... but it might be exaggerated with the DS connected.
