Hey there...

Trying to track down a drive train vibration that is driving me crazy. Car is an '84 245, B23F, M46, about 400K miles.

Within the last three months, the motor mounts, transmission mount, u-joints and center carrier have been replaced. The mounts were completely trashed. Replacing them made the car WAY quieter and smoother.

And the u-joints and center carrier were in pretty bad shape, too.

But the vibration persists. It happens only in 1st gear between 10-15 mph, and only while accelerating. If I back off the throttle and hold the car's speed at say 10 mph, there is no vibration. But as soon as I give it more gas and start accelerating, the vibration is there up to about 15 mph. I've taken it up as high as 25 mph in 1st (about 5,000 rpm) and there is no vibration. It's just in that 10-15 mph bracket.

The vibration can be felt through the floor and through the pedals. It's enough that the headrest on the passenger seat visibly vibrates.

Any ideas? Thanks!!

Hi,

You have brought up an interesting subject, vibration.

I have always thought that the 1984 model car, that I also have, runs differently than my B-21 1978 and my later B-230’s. The B-23 was a little stronger for the cc’s but did not rev as freely as the smaller engine.
The 84 seems to be more low end torque minded. IMHO.
Between the 78 and 84 the engine size, likewise changed, so I wrote it off as, that is where the more power band ended up.

Since the B-230’s came on line in 1985. I noticed my 1986 engine ran more smoothly. I wrote it off to the LH 2.2 improvement to adjust that torque band.

Now I want to say, that on the B-21 of 1978, there is no Harmonic Balancer on the crankshaft at all. They even used a split pulley to adjust the A/C compressor belt. No consideration about harmonic resonance.
I’m not where I can look at my 1984 to see if it has one but I know my 1986 does.

So if the change in engine size warranted a balancer, does the 1984 have one, I ask?
If so, if it goes bad, like the rubber get hard or splits, what happens? Vibration?

I looked this up on the web. https://en.m.wikipedia.org/wiki/Resonance
It appears from the information, it is a very good possibility that a engine can exhibit more harmonics in first gear. More so, than in any other gear.

What goes on inside a engine is the crankshaft bends or is flexing as it rotates from the pistons and rods pushing. This changes the radius or balance of the crankshaft, of which, shakes the engine at certain frequencies or amounts of pressure.
Since it is more noticeable in low gear the revs are more easily obtained with the load drastically changing from a dead load pull away to the crankshaft gaining inertia. You can actually dial in the revs to the load and set up a fixed frequency. Engineers do not like this!
The idea I got from the articles I found is that the motor mounts play a big part but if they cannot handle all of the vibration the harmonic balancer is suppose to help keep it isolated to a narrow band that the engine can survive. Maybe the band is wider than it should be and consequently more noticeable.

How it all works is well beyond any of my experiences.
There is a part about it having to be an interference fit onto the crankshaft. I have not seen this while doing timing belts. They are not made on to be put on there that tight, but it fits nicely!
They also want the crankshaft bolt tighten to a certain stretched specification.

So with all this said, you might want to give this item a good look into! I know the rubber layer does go bad on these.
Seeing something obvious is probably not how it’s going to work. That’s my experience.
Substituting another use one might change it a little bit, if it looks better that the original and making sure it’s TIGHT!
Apparently I see these offered as with your new motor mounts.
I have read about it being hard to get good rubber parts I hope this is not leading us to be more dependent on Harmonic Balancers.

Hope this helps with your craziness?

Phil

I do not think that the '84 has a harmonic balancer, but it is too dark and too cold outside for me to go look. :-)

I have noticed the same thing about the B23F. It has a surprising amount of low end torque. Enough that you can shift at < 2000 rpm and still have good acceleration in the next gear. But it DOES NOT like to rev over 3000 and sounds like it is going to come apart if you push it hard. The older B21 and later B230 do not complain in this regard.

No harmonic balancer oscillator crank pulley on your B23.

I'll guess you read the manual transmission netry in the 700-900 FAQ?

Transmission:Manual, Clutch
https://www.brickboard.com/FAQ/700-900/TransmissionManual.htm

Harmonic balancer oscillator crank pulley is on low friction three-number redblock engines only. (I forget whether the B2304 quattrovalve engine has a harmonic balancer, tho irrelevant.)

If you have gear whine, how is the fluid? Can't make metal grow, yet can quiet if trans fluid is low or old or wrong. The Amsoil Super Shift Racing Transmission Fluid SAE 10W works wonders in at least M47 and should for M46 & overdrive.

Also, how is the clutch adjustment? Proper 3-5 or so mm freeplay at the throwout arm? Cable slides through sheath easily? These can fray and eventually break.

Keep your foot off the clutch pedal at stops. Press only to engage / disengage.

Though at 400k miles, input shaft, main and lay shaft bearing wear, as well as clutch bits, can be suspect, as you stand advised by your other helpful respondents.

As you had your drive shaft out, did you check torque of the nut that secures the M46 output flange?

If you had M47, as Old Duke has, I would be suspect of the flex disc coupler giubo (some call guibo as Art corrected all of us earlier this or late last year in a thread). Also, I've found the M47 output flange retaining nut barely to snug, not to torque a few times.

Input shaft whine and throwout bearing whine may sound similar. Though T/O bearing quiets when pressing the clutch pedal usually, unless severely worn. Dunno if input shaft bearing whine quiets whether clutch in / out / or in neutral in or out.
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hi cd - thats a funny comment about the volvo 240 4cyl engines. have heard more than one volvo mechanic, even the dealer mechanics make fun of the engines and call them tractor engines due to their torque characterstics. i suspect while it makes the engine slow on launch at lights(with the resultant vulgar hand gestures and f bombs from drivers behind you), it also means the engine seems to last longer(doesnt work as hard) than many others. my 92 245(b230) has 250k, doesnt burn oil and runs like a mutha(asbury park jargon-sorry). regards oldduke

What about the OUTPUT bearing/bushing (whichever it is)? That's the one that would experience the greater variance in torque load between low gear and higher gears.
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Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (getting ever closer to road worthiness)

if you look at a graph of torque overlaid rpm's in various gears on the m46 i think you will find the speed range in first gear that causes the most trouble is the maximum engine torque output for that gear and probably for all the gears on your setup.

high torque greatly exacerbates the movement in anything loose/out of alignment within the drivetrain.

hi cd and trich- this a a very annoying problem. i have exactly the same thing in my92 245 with the m47. thevibration occurs at the same time in 1st gear but when the car is warmed up and at no other time. went over the whole drive line with a friend and volvo sage and found no problem with the usual suspects, u joints, engine mounts, clutch, t/o bearing, cable, fork, carrier bearing, driveshaft. not wanting to suffer the severe sticker shock to be suffered when inquiring about a dealer inspection, decided to put up with it . thinking now it may be a weakness of the volvo manual trans like the m 46 and m47. do know that there is a lot of stress on the input shaft bearing of manual transmissions when launching in 1st. saw a lot of this problem on american 3 speed manual transmissions from the rwd era. seems i have eliminated every other cause. what is your take on my theory valued sages? thanks tons oldduke

if i were to speculate on the source of the vibration my focus would be within the transmission or the flywheel.


if the flywheel is not truly flat or the clutch disk has worn so its not parallel with the flywheel as it grabs i could envision vibration transmitted though the drivetrain under high torque conditions

The clutch was replaced about 3 years ago. I've driven the car MAYBE 15,000 miles since the clutch job, and that is probably generous. I started a job that I can walk to/from about 5 years ago so the car is only used for weekend trips and convenience (rain, extreme cold etc.).

My old Volvo Indy retired when the lease on his shop came up and the owner of the property refused to renew it. So, this last clutch job (I've only done two in 400k!) was done by another local shop that specializes in transmission/rear end work. They are NOT Volvo specialists, but they have a good reputation, and I figured that replacing the clutch in a 240 is about as easy as clutch jobs get.

I would not be shocked to learn that they f-d up when installing the new clutch. I asked them to use OEM parts and they showed me the Sachs box that the clutch kit came in (they ordered from iPd - ha!). But if they were in a hurry who is to say that something wasn't torqued down all the way or that the t/o bearing was not properly greased. The flywheel was SUPPOSEDLY resurfaced, but I couldn't prove it.

hi trich- think youre right if that was the problem . rarely saw that exact problem but if so it would soon degenerate into clutch chatter which is much more noticeable. if so you have to determine what unparallelized the pressure plate and clutch disc. could be something as simple as unevenly torquing the pressure plate hold down bolts or leaving one lose or even a warped flywheel(unlikely). could also be caused by wobbling input shaft(more serious). remember always check the simple stuff first(leads to much less use of profane language). regards oldduke

Oldduke,

You are thinking along the same lines as me regarding the input shaft. My gearbox (m46) developed a whine in the lower gears (1st and 2nd) around the time that this vibration reared its ugly head. It's not loud and can only be heard when coasting with the clutch pedal "in", but it's definitely related to the vehicle's speed. If I am coasting downhill and take my foot off the brake, the whine increases in pitch as the speed of the car increases. It goes away when I shift into 3rd. It is not the "whir" sound that you get with a bad t/o bearing. Hard to describe but it definitely sounds like something is on its way out. Input shaft bearing? Main bearings in the tranny?

hi cd- have to admit , dont have any experience with the m46, only the m47. have heard from the m46 overall is more of a heavier duty trans than the m47. go up and down a hill in first, accelerate up the hilland coast down the hill. if up the hill (high torque load) and down the hill(low torque load) there is the same whine it may suggest a worn bearing on the input shaft. if no whine down hill then the bearing is likely ok unless there is a clunking which suggests a damaged gear tooth or teeth. saw this more than once on american 3 speed manuals of yesteryear. just my
$.02 . regards oldduke