mark kibort

Good Idea Greg...… I usually change the Redline gear oil once a season, but since last season was kind of short, I lengthened the change interval..... this is a good excuse to get that oil out of there and check for "pieces" and change it too. any thoughts on what could break on the main input gear and shaft that could make a vibration at a specific range of rpm (5000 to 5500rpm) , regardless of gear selected?
thanks

G8RB8

What do the tranny mounts look like?

FredR

Mark,

I looked in good shape 10 years ago now I feel knackered after formally retiring! Your car is 30 years old, 10 years ago it was 20 years old - things that are aged can and do go downhill rapidly - it is a law of nature- they wilt and die off- your cables are no different. The picture you posted shows most likely knackered cables no matter whose it was and when the pic was taken albeit I was confused as to how you had magically repaired it. If you think yours are going to be any better dream on-

Water is not really the issue- it is heat and you race in it. Mine saw no water whatsoever and were nicely corroded under the crispy fried remnants of what used to be insulation when it was first put there. Of course if such were to get doused in water it surely would be the icing on the cake!

mark kibort

haha.... yes, I know the feeling.. But, I seemed to be recovering from my aging over the past 5 years. I don't feel a day over 45 now! anyway yes, there has been time and heat, but actually when the car runs, it doesn't sit in traffic! it doesn't sit outside, it doesn't see water when its racing this part of the car sees 80mph average speed air.... so, its no wonder the wires are actually in good shape vs cars that due "street " duty. below are the pics.... btw.... so that smaller 10mm brown wire in the red loom, goes back to the alternator, along with the larger one,which ends up at the ABS UNIT? the heavy black wire comes from the positive battery terminal. (not in my picture)
take a look..... I can ether solder (which I did and wrapped), or find another ring terminal to stack on the one that is left. I don't have a crimper that large , so im thinking of replacing both of them with slightly smaller crimp terminals. however, there might not be room on the stud (starter /solenoid) for it

the temp fix at the track was to crush the open wire under the nut

the broken wire off the main terminal that attaches to the starter along with the the main black wire from the positive battery terminal.

GregBBRD

Migrating torque tube bearings?

Mark Anderson once had the front torque tube bearing slip back, at an event. The vibration was so bad, the hot wire in the MAF broke.

FredR

Mark,

I think I need to visit the emergency department at the local hospital- I think I have ruptured myself laughing so hard!!!

That lot in the orange sleeving is shot- you need to rip it out and start again. Give Sean or Greg a call and get some new wiring or purchase a decent crimper & DIY. Repair? you have to be joking. Look at the insulation on the solenoid terminal- it is falling off. The colour of the cable cores tells you it is in dire condition and as for the insuation - urrgh. The cable from the battery is probably OK but the rest of it forget it.

Now take a look at what I wrote earlier on your vibration issue and particularly so the engine mounts. If they experience resonance type vibrations due to collapse, if you have torque tube bearing mounts that are badly aged/shot what do you think might happen to them if the resonant vibrations hit them? Think cause and effect- if the bearings have migrated as the root cause then the shaft is going to flex differently and good chance you will feel it in knackered mounts. If knackered mounts are the root cause the excited vibration will send tired bearing mounts for a walk,

The rules of wear and tear apply to your goodself just as they do to the rest of us idiots - probably more so I would think. Hopefully your dear Amsoil protects your engine and nothing untoward going on there however vibrations are a warning sign that all is not well and not necessarily early warning signs and once they start who knows where they are going to end up and screw up - take note and action- ignore at you peril!

mark kibort

it certainly is a resonance caused by an imbalance . because the vibration is only in gear and under load, im thinking transmission. but the vibration is very similar to the high speed vibration 4k to 6k of the throwout bearing out of alignment with the C-clip partially coming out.. do you remember if the vibration Mark had was at all RPM? is there an easy way to check it?...………….maybe a long piece of wire that is fed from the front coupler , rearward? where are the bearings supposed to reside?

I just took it out for a spin.. smooth as silk up to 4500rpm..... not too bad at 5,000rpm , but as soon as load is added, you can feel the growling of vibration. im wondering what , if anything could cause this in the transmission? the bearing moving in the torque tube sounds like a reasonably likely cause...……..especially since mark A racing his , had that happen.

thanks, ill pull off the bell housing and see if I can get a sense of where the front bearing is. il also get it on jack stands to see if there is any bearing noise I cant hear in the car.

one other thing...…...I was thinking one of my "pins" on the H adjusters might have broken free and the intermediate plate might be not aligned, but that should only effect it with the clutch separated, not pressing..

mark kibort

well, yes, the insulation is very old . no cracks but yes, you can tear it off much easier than if It was new. keep in mind, its covered in the bright red insulation which is in perfect shape all the way to the alternator..... the insulation on the deep angled solenoid terminal, is slightly exposed, but that's not like the 1000s of wires and connections on the car that look similar. things that are critical , like spark plug wires, coil wires, main positive hot wires are insulated and look fine some of these smaller wires are covered with no cracks, but the insulation is aged. it doesn't mean they are not working, in a perfect world, I would want the entire chassis rewired, but that's not going to happen. this particular junction is soldered up and insulated with an shrink-wrap. . I'm not terribly worried about it, as if it breaks in the patch up …..what is the worst that can happen? I loose my ABS and the gauges go nuts again?? not a big deal actually.. the wires are NOT green with corrosion like yours. the ONLY problem is that the moving of the wires off the starter 10s of times for clutches, etc, has weakened the wire, and that's why it broke off. bending back and forth at a pinch point broke the wires. classic metal fatigue... I've secured it so that it can move now as well. the engine mounts are fine... compressed but working.... the transmission mounts seem to be in place and working as well. im thinking something has created an out of balance situation where we now have a resonance at 5000 to 5500rpm. as you know, resonance is a frequency that is excited when you HIT that frequency (rpm)….. some out of balance resonances are in narrow ranges and some have excitations that cant be overcome with frequency. (like my out of balance throwout bearing vs this current vibration...… 4500 rpm to 6500rpmm bad vs only bad at 5000rpm to 5500rpm)

I appreciate your feedback, but trust that I'm not going to just let the car fall apart . I'm not as **** as you are on many of the fixes ive done... most of which have lasted this platform for 20 years of pretty hard racing and a few have caught up with me. Dr bob gave me a HUGE hard time about not changing the front wheel bearing pressed in races, only the bearings, using the old races.... I gave him my theories, pictures of the bearing wear magnified, and reasons of why they would be fine. The proof in the pudding, 5 years of racing later, they are still working fine. so is the pinned intermediate plate, and many other creative fixes I felt would work fine for my uses.

GregBBRD

Torque tube shafts tend to flex under load, although when the bearing moves a long way, the shafts will shake in neutral.
A quick clue is if the short clutch shaft has been contacting the T/O bearing support collar. Mark Anderson had a shaft that had hit the collar and got hot enough to machine itself down, turn red, and twist into two parts. I'm sure he has a picture of this shaft. Pretty cool.

The plastic bushing which goes between the torque tube shaft and the torque tube bearing can also deteriorate and fall apart (common).

If you remove the lower cover, a small mechanic's mirror (dentist's mirror) and a flashlight will let you see down the torque tube shaft to the first bearing.

It should be about 8" from the front of the torque tube. The plastic insert should be visible....although it's black and sometimes difficult to see. If you can see air between the shaft and the bearing, it fell out.

FredR

Mark,

Believe what you choose to believe but if you can pull insulation off the wire its well and truly F***ed. I am confused as to where you actually saw red insulation- most certainly not in your photo and you can actually see cracks in the cable powering the starter solenoid- all classic signs seen many times over on heavens knows how many examples. On the cables from the battery compartment to the starter motor, the alternator, on to the hot post and ABS post, and then through to the central electrics with a battery that in good condition can instantaneously dump about a 1000 amps to earth if anything on that system grounds to earth due to failed insulation what could possibly go wrong?

As to the bit about "the wire popped out because of clutch movements"- have you ever heard of copper suffering from fatigue failure- crikes! Copper is not only an excellent conductor it is extremely ductile otherwise it would be no use in cables. If what used to be copper fails like that it is no longer copper- did I see black shards on your towel- do you know that cupric oxide is black?

Something out of balance is completely different from something that is resonating. Resonance occurs at specific speeds, something out of balance gets worse the faster it goes. Change the position of a bearing support and something can easily get excited if the resulting free span is inadequate. There is a reason why Porsche used the hydraulic mounts they did and it was not so that over time they could go soggy! As I said earlier think cause and effect.

Way past my bed time - look forward to seeing what you can concoct next.

mark kibort

Thanks Greg! yes, makes sense that could be the issue.... talked to Mark about his issue..... said it was about 12" down and that is way too far when his gave that big vibration... he said he just put another bearing carrier down the tube after removing the clutch and short shaft... good idea??? sure would save time from removing the torque tube.
ill use a coat hanger and use the peek hole (coupler tightening hole) and see if I can get a distance to the bearing to see if it moved.

got a break in the rain... checking in a few...……...

mark kibort

Fred , im not in disagreement. but the corrosion and issue with the wire the part I cut off. it looked pretty clean and shin

y after the cut and on the other wire still attached, it looked good... however, that one might have some signs of fatigue … not the "clutch moving" but me moving the lower bell housing with the starter attached all those times, fatigued the wires at the coupling. here is the fix..... as far as the "red insulation" im talking about the cover that follows the two wires to the alternator. nice and shiney red. the wires covered with the brown insulation is not and was never red new ( I don't think)… but the insulation is certainly weak, but not cracked or exposing any wire . and yes, if it was and it grounded that would be a HUGE issue... so, ive inspected it pretty well.

Regarding the out of balance.... sure, I agree, that cant change a resonance point... so it probably is the torque tube bearing if I was to guess... the out of balance I had with the TOB didn't get better with RPM.... I suspect this issue, has to be a damping issue...… ill know more when I measure the distance of the first bearing of the torque tube.

thanks again!

your funny... your last comment.

FredR

Mark,

Try reading my posts and the wiring diagram occasionally-

The "insulation" you refer is the protective sheathing- it is fibre glass with a rubberised outer sheath- it is excellent material and does not seem to degrade- I would not call it red rather an orange colour but whatever. As I have tried to advise you on a number of occasions the cables are fire engine red- what you see is the manky colour they degrade to when the insulation is shot- this happens on all 928 engine wiring harnesses sooner or later. I refer to it as "cable cancer". The integrity of the cable is only as good as the conductors within and the insulation. IF you have the time and inclination post a picture of the cables as they enter the 14 pin connector and entering/leaving the hot post. I suspect at the hot post you will see the same manky brown colour entering the hot post and take a careful look at the two red cables leaving the post as they sweep through 180 degrees on their way back to the central electrics- hopefully they will still be red. Ask Carl what happened to the 928 that was in his shop just parked there doing nothing..

What is not clear is how you "repaired" the cable at the starter motor. The photo suggests you used the same crimped lug somehow- maybe you managed to stuff the cable cores back into the hole they came from, taped it up and called it quits -not exactly what one would call "kosher". Even if the cables were good [which they are not] you need a new lug and a new crimp to make the joint. Flex those cables and I can almost certainly guarantee the insulation will crack. Inspect the cable carefully for the last 6 inches or so before it connects to the hot post.

It will be interesting to see where you find the TT bearing- trouble is there re three of them in your TT and you can only see one of them but it would be a start.

mark kibort

I don't know if those two cables were ever "red", (the ones you call "wonkie" and are brown now), but the insulation is intact and even though a little soft, there are no cracks. the solenoid wire is cracking at the insulation. I didn't just stuff the wire into the ring terminal … as I mentioned, it broke off because of metal fatigue.. so, I trimmed the loose wires, as you can see from the picture on the towel and then I soldered it to the main wire at the point it joins the "lug". I used a very powerful soldering iron and rosin core solder. (and a lot of it) I did it twice to make sure I didn't get a cold solder joint.. then wrapped it with insulating tape and secured with a tie wrap. in the mean time, ill look for some "crimp lugs" and find a tool to do it right as there is plenty of length to work with . but for now, this is the temp fix

Ill take a look at the 16pin connector near the hot post. where did carl's short out? the wires all look good going back to the fuse panel and the main power to the power post looks old, but solid , no cracking from what I remember.

as far as the torque tube, yes, there are 3 bearing carriers, but the ends are probably most important and sensitive to position I would think... I guess the more one of them moves rearward from the clutch side... I imagine the worse it gets. I guess the good news is , its not pointing to something in the transmission, but Ill still change the gear oil and see if anything comes out.. I can also pop the top cover off to look inside the transmission as well..

FredR

I do know and they were red- look at the wiring diagram.''

Given how you approached the repair be aware that the other core that remained inside the crimped terminal is now compromised by nature of the cable that is not there. If you managed to flow solder into the ring terminal and get it to flux that may be OK but if you do not know that just be aware it may let go. The soldering sounds as though it is the kind of job you need to do with a MAPP torch.