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BillWilliams

Guibo Failure

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There is an ongoing problem with premature guibo failure. Premature may mean guibo failure in less than 5,000 miles.

A failing guibo will manifest itself with a rattling, bumping, thumping sound coming from the transmission tunnel area. Often it happens when starting out. If this symptom(s) happens, you have time to get home and get it fixed. These cars are kind enough to let us know when they need attention. (Just like a kid, if we don't pay attention to them, they will find a way to get our attention.)

This failure often happens after a five speed transmission swap.

Cause of failure: Misalignment of the flange on the transmission and the flange on the drive shaft or a drive shaft out of balance.

Cause of misalignment:

1. Flange on shortened drive shaft welded on crooked.

2. Transmission and drive shaft out of alignment.

This is not a technical discussion with words about planes and axis, I am not capable of that. This discussion is just about how to fix the problem.

Fixes

1. Crooked flange: get it fixed by a reputable drive line company

2. Out of balance drive shaft: Have the drive shaft balanced by a reputable drive line company. Note: anytime you take the drive shaft apart to service the center bearing, index the two pieces. (Indexing means mark both pieces of the drive shaft so you can put it back the way you took it apart.)

3. There are several ways to determine if your two flanges are out of alignment. I will cover one way, other posters may add what works for them.

With the car securely on jack stands, or a lift if you a fortunate one, install a new guibo but install it loosely. Loosely means where you can see about 1/16" of a gap between one side of the guibo and the flange. The other side of the guibo should be tight against the other flange.

Car is in neutral e-brake released.

Now, with a very good light, I like those pen LED kind, a Stylus is the brand name, rotate the drive shaft.

While you rotate the shaft, watch for any change in the gap. Look at the sides AND at the top and bottom.

If you see any change in the gap, the flanges are out of alignment. This must be fixed or be prepared for roadside guibo changes in 1,000 miles or less.

The fix for this gap depends on the way your five speed transmission swap was installed. Each five speed conversion method/kit will have a way to align the transmission to the drive shaft.

You will have to figure out how to get that gap to stay the same.

Install the guibo in accordance with the blue manual repair manual. Head of bolts on the guibo, locking nuts on the flanges. Only tighten the nuts. Tightening the bolts will/may separate the bond between the metal tube and the rubber on the guibo. Use the correct bolts and new locking nuts. Torque to spec, this is hard because you can not get a torque wrench in some places. A flex head ratcheting wrench is good to use here.

If you are dealing with a four bolt flange, eight hole guibo, the guibo will have a metal band around it. Do not remove until your installation is complete. But always remove it before driving. I have not seen any of the six hole guibos with bands, some say there is one type with a band, treat it the same way as the eight hole guibo.

REMEMBER, be safe and when rotating the drive shaft, look side to side AND top and bottom.

Also, check that guibo every time you are under your car.

If you are having problems, carry a spare guibo and nuts and bolts. (sorry CD)

Six hole guibo and three bolt flange on left

Eight hole guibo sans the metal band on right

IMG_3150.jpg

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I think the first things to do are to make sure everything is installed properly:

Guibo bolts installed and tightened properly?

Preload on center support bearing?

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To align the driveshaft to the transmission you can:

1) Raise the rear transmission mount height with shim washers.

2) Lower the center bearing height with shim washers.

3) Relocate the rear transmission mount adapter that you used.

Other thoughts?

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Lay under the car and with a bright light so you

can SEE what's happening - rotate the drive shaft

(yes the rear wheels are up off the ground supported

with JACK STANDS) AND WATCH and LISTEN to

the guibo as it rotates. It should NOT squeak from

flexing, or wobble as it rotates around. It should spin

perfectly TRUE.

Guibodrawing.jpg

By shimming up the transmission mount, shimming down

the center drive shaft bearing mount - or any other

way that's needed, you achieve a straight line passing

through the drive shaft ---through the trans

output shaft -----------------------

When installing the new quibo - leave the metal band

on it until everything is aligned and tightened. Tighten

NUTS - not bolt head, And the nuts with washers go

to the metal flanges - NOT to the rubber guibo.

THAT WAY your not twisting a nut tight while twisting

the rubber which will cause it to fail instantly. USE ONLY

BMW hardened bolts and special lock nuts, and blue 242

thread locker on clean threads - ESPECIALLY if your reusing nuts.

----- - so half of the bolts insert from the rear,

the other half from the front.

There needs to be a grease seal with bushing in the front

of the drive shaft also to center and support it on the

trans output shaft, and packed with high temp

MOLY bearing grease.

If your drive shaft has a splined joint, that is also greased

with MOLY LUBE and left loose so the shaft may expand while

all the other points are attached - the drive shaft sliding spline

nut is THE LAST THING TO TIGHTEN

guiboinstall.jpg

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Drive shaft alignment tool:

http://www.bmw2002faq.com/component/option,com_forum/Itemid,57/page,viewtopic/t,273614/highlight,driveshaft/

Drive shaft alignment method.

http://www.bmw2002faq.com/component/option,com_forum/Itemid,57/page,viewtopic/t,306648/highlight,alignment/

With everything that has been said, the only thing to look at if the guibo fails is this picture as its the only cause of the stress on the guibo...all the rest doesn't have impact on the guibo itself, or very small impact.

The alignment of the drive shaft itself, with the use of a tool, should result in smooth drive line.

Guibodrawing.jpg

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Guest Anonymous

Also make sure driveshaft is right length after a 5-speed conversion. If there is a gap between the flanges and the guibo, closing the gap by tightening the flange bolts will distort the guibo and subject it force along the axis of the driveshaft. The fix is to loosen the diff and slide it forward in the slotted holes until the gap is closed. (Also loosen center bearing and adjust its preload after diff tightened back up.) If diff too set too far forward, this will distort guibo in the opposite direction, though it would be hard to get the driveshaft on in this case. Neither is common, but could be mentioned in the FAQ.

Fred

'74 track car

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Guibos and Center Bearings for Dummies

Whether it’s a vibration at 40 mph, a howling noise, clicking noise or any other strange clunks and bumps coming from under your 2002, one of the first places to look is at the driveshaft.

Assuming your driveshaft is properly balanced, which is required, the two biggest causes for the previously described conditions may well be either the guibo (flex disc) or the center bearing. Or both.

My $750 1976 project car (4-speed manual) had countless miles (over 150,000) and lots of hard driving logged over the years. These parts wear out. The car drove ok up to about 50 mph. At 50 I could feel a definite vibration. Also, in first or second gear at low speed, backing off the gas pedal produced a distinct clunky jerk. If there is such a thing. Upon inspection, the center bearing was shot. Visually, the rubber portion of the piece was cracked and separating. By grabbing the driveshaft and pushing up on it, it clearly moved within the center bearing housing. When the rubber goes, it’s shot. Replace it.

While under the car I took time to look at the guibo (flex disc), that rubber donut that connects the front of the driveshaft to the transmission. The guibo is about the size of your fist and on my ’76, there are 8 bolts that hold it in place and hold the driveshaft to it. I could rotate the driveshaft and see at first glance that the guibo looked good. But on closer inspection I found three very thin cracks that looked innocent enough.

However, since my center bearing needed to be replaced, and the driveshaft must be dropped to install a new center bearing, it only requires removal of four more bolts to change the guibo. Do it while you’re there!

You can buy guibos and center bearings at the BMW dealer, BavAuto, Autohausaz, from board members and a variety of places. Get new ones, not used. Unless you like changing them. I’ll let others argue OEM vs. aftermarket.

When I removed my guibo, and held it in my hands, those 3 little cracks were actually 3 breaks that went completely through. The bolts held it in place, but it was only a matter of time until it came apart. It came apart easily in my hands.

Here’s the procedure as done by me, a novice mechanic with little knowledge but some ability. The biggest difficulty (hopefully) is working on your back with the car on jack stands. But it can be done.

If you can shoot some Liquid Wrench or similar on a few of the critical nuts before you start, like the large nut holding the two pieces of the driveshaft together, it should make the process easier.

For the first step, raising the car, I steal from Rob and Trent in their 5-speed Transmission conversion article:

“The first thing you need to do is SAFELY elevate the car and put it on jackstands. Ideally you would pick a flat hard surface in a level location (such as inside your garage). If this is unavailable you can do it in the driveway, but make sure the e-brake is on (and working) and/or you have securely chocked up the rear wheels. Start by putting a 2x4 across the cradle of your floor jack to spread the weight a little and lift the car at the center of the front subframe. If you are on a soft surface (NOT RECOMMENDED!), use thick plywood or equivalent to keep the jack and stands from digging into the surface. Place a couple more 2x4s on top of the stands and then position them under the stamped steel frame rails attached to the front floors of the car. Then, if you are on a flat surface, you can raise the rear of the car in similar fashion, placing the stands under each end of the rear subframe, just next to the mounts. Make sure the whole thing is rock-steady before crawling underneath! Use good quality stands and/or ramps because cheap ones can collapse! Remember: Safety First!”

Starting in the rear, from the passenger side of the diff, look up in there and you will see one or two of the nuts holding the rear flanges of the driveshaft. With the car in reverse, and the parking brake engaged, reach a 17mm box wrench up in there and break loose the first or the first two nuts you can reach. I could only reach one at a time. Once the nut is loose, get up, put the car in neutral, and rotate the driveshaft till you see the next nut. Put it back in reverse, parking brake, etc. Lots of up and down but it works. Others have stuck a tool into the driveshaft near the center bearing to keep it from spinning while it’s in neutral, to avoid the up and down. Whatever works.

With the rear nuts loose, or removed, move under to the guibo from the drivers side. Disconnect the exhaust at the downpipe connection. You should be able to just move it to the side enough to be out of the way. Remove the exhaust if you want to.

Most likely, when you look at the guibo, four nuts will be facing back, four nuts toward the front. That is the recommended way to install them for the sake of undo pressure on the guibo. Others argue if they face all nuts to the front, they are safer if a nut ever comes off and the bolt falls back instead of eating the trans. That’s an argument for others. The Haynes manual shows four front and four back.

With that 17mm box wrench, and a 17mm socket, you should be able to remove the four bolts that are holding the front driveshaft flange. You might be able to accomplish these bolts with the car in neutral, and just rotate the driveshaft until all four are off.

If the nuts are frozen, and you damage them in any way, buy new ones. Some people insist on new ones anyway. If they come off without undue hacking, cutting or heating, they may be reused.

Now with the front and rear flanges unbolted, remove the two nuts holding up the center bearing. Be ready to catch the driveshaft as it drops. Give yourself a pat on the back when the driveshaft hits the floor. But there’s more.

Now go back under there and take those final four bolts out that are holding the guibo in place. Slip the box wrench up behind the guibo and use the air wrench if you’re replacing the guibo. Now for the fun.

At this point, be sure to take some paint and mark a straight line from one piece of driveshaft to the next. It is imperative that you join the two shafts together exactly as they came apart. If you don’t, you can expect your driveshaft to be out of balance and bad vibrations will be yours.

With the driveshaft marked, take a 24mm box wrench to that big nut that joins the two driveshafts. I bought a cheap wrench at Autozone and it fit inside the tight spot with no modification needed. Others have taken a 24mm or 15/16ths box wrench and ground it down to fit. If you soaked that nut for a few days with Liquid Wrench or similar, simply break it loose. You can put the shaft in a vice, at the u-joint knuckle for leverage. Others have used big pipe wrenches with some success. Just don’t damage the driveshaft or the u-joints. Common sense.

Once again, with the driveshaft marked with paint, remove the nut and pull the two driveshaft pieces apart. Your next move is to remove the old center bearing. The bearing is pressed on and is not easy to remove. Get a gear puller. Again, Autozone sells a 5-ton 3-jaw puller for $22 and it’s worth every penny. Attach it, turn the bolt on the puller and the old center bearing will slide off. If you think you can simply tap the old bearing off with a hammer and punch or similar – good luck. Don’t damage those splines.

Time for the reinstall.

Carefully put the dust cover then the new center bearing on the driveshaft in the same orientation as the one you removed. If you didn’t buy that gear puller you probably spent an hour or more staring at that old bearing, trying to get it off, so you should remember the orientation. The open face of the bearing faces forward. It will slip on the splines easily for the first few inches, then the tight fit comes. Very carefully, press on the new bearing to the same spot where the old one sat. It’s important to get the bearing all the way on to where it should be so everything lines up and works properly. I had a piece of pipe that was the same diameter of the inner bearing. I gently tapped it into place with no damage. If you’re worried about damage, take it up to your mechanic and he’ll press it on for a few bucks.

Next, attach the two pieces of driveshaft following your painted lines to be sure your driveshaft remains balanced. Re-install the large nut that was so hard to get off. Some use Loctite on it, others do not. Mine had none, and I put none on. I torqued it to three grunts.

Before you reinstall, it’s a good time to service the shifter linkage, tighten the shifter plate or replace the tabs that hold it in place, and change the transmission fluid. Be sure to loosen the fill plug on the drivers side of the trans before you drain it. Both of my plugs take a 17mm allen head but there is very little room to access the refill plug. I cut down a bolt and used a pair of vice grips to open it since my socket wouldn’t fit up in there. Also, when I drained my trans fluid I got out about a cup of liquid. That’s it. It should hold 2.94 US pints. Glad I checked before this project hit the road. Read all the other posts for the debate between ATF, synthetic and hypoid.

Ready for the re-install. But first, attach the guibo to the trans. Do not remove the metal band around the guibo until everything is installed. Just don’t do it. It makes the install easier by compressing the rubber guibo. Put all 8 bolts into the guibo, 4 forward, 4 back. Push the four bolts facing forward into the four flange holes of the trans. Reach behind and install the 4 nuts to hold the guibo in place. Use your box wrench to tighten the nuts against the flanges, without putting a lot of stress on the guibo,

With the guibo in place, and 4 bolts facing back, jockey the driveshaft back up into position. With the driveshaft somewhat in place, you can apply the two nuts to the center bearing to support the shafts. But don’t tighten down. Tighten these two nuts last.

I reinstalled the back flange bolts and nuts first, the ones that go to the diff. Reverse your removal procedure but don’t tighten everything down just yet, just tighten them into place.

Now reinstall the four nuts that hold the front flanges to the guibo. The driveshaft should fit in their snugly. Again, tighten the nuts against the flange to keep stress off the bolt heads on the guibo. Tighten your bolts to the diff if they are still loose. Now for the center bearing.

The driveshafts should look pretty straight. When you tighten up the two nuts holding the center bearing, the driveshaft should hang straight. There are a variety of ways to assure straightness. An actual tool, which no one owns, is the best method. I used a straight piece of 4-foot 2x4 that I notched for the center bearing and u-joints. Others have used broom sticks, sockets and other inventive tools. The 2x4 seemed to work great. Tighten up the center bearing to its tight position and place the alignment tool (2x4) up against the two pieces. That 2x4 should lie flat against both halves of the driveshaft. Rotate it and re-check for straightness. If not, you have to go find where the problem is, and it may be at the guibo. A washer or two may be needed. But mine went back in perfectly (as it should) with no problems.

Knowing that the driveshaft is aligned, loosen the two nuts holding the center bearing and push the housing toward the front of the car 2mm to preload the bearing. I’m smart enough to understand preload but moving it 2mm seems kind of senseless to me. But that’s the spec. Move it forward 2 mm and tighten it down. With all bolts and nuts tight, the center bearing preloaded, now cut off the band on the guibo.

That’s it. Re-connect the exhaust and get ready to smile. If done correctly, you should notice all kinds of improvements, depending on how bad your pieces were before you started. No more clunks, no more vibrations, your car should be fun to drive again. And you saved $250 or more by installing these pieces yourself.

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What I have done in the past, and I am not sure I just got lucky but it seems to work, and intuitively I think it should: I tighten the drive shaft to the guibo and to the tranny and the other end also to the differential. I snug the bolts on the center support, then slide the differential back with two large bars (to make sure is being pushed equally). Then while I am putting a load on the two bars I have somebody tighten the differential and the center support. Never had a problem with vibrations. This method requires a smart helper though...

I think it would be hard to rotate a wet noodle, but if you pre loaded then your odds of spinning it without vibration are much better.

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a thorough description on how to align the transmission/driveshaft to the dif would be helpful

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alfas have been using guibos since the middle 1950's.

with the giuliettas (103hp or less) they hardly ever failed.

with my milano (188hp) failure can occur at 6 yr intervals (65000 miles). looking down through the engine bay (there is no bell housing since the clutch is out back), you can inspect for cracks.

my zink mk.3 running a cosworth mk.13 (155hp +/-, one guibo on each half-shaft)) used to tear them up regularly, angularity was excessive.

> jack

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Just an observation, but it seems to me that preloading the center bearing is really just a way of keeping forward tension on it, so it can't vibrate/slip off the shaft. I could see no real reason otherwise.. They are removable by just tapping the DS on the floor.

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Just an observation, but it seems to me that preloading the center bearing is really just a way of keeping forward tension on it, so it can't vibrate/slip off the shaft. I could see no real reason otherwise.. They are removable by just tapping the DS on the floor.

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