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no good about the gearbox Mal, its a bit disappointing when you take it 2 hrs to a specialist for zero result.

it sounds like your setup info is the same as mine, but i never heard anything about the max angles on the unis .... might be worth checking mine just to see where they are at!

Malcolm wrote:Hey guys, the gearbox is still shit. After a 2 hour drive to the diff guys it came home still stuffed.
Now it only brining up the 1 code (85 Transmission slipping) and there saying its the converter causing the problem as when its slipping when locked it goes into safe mode stopping it from changing into top and recording the 85 code.



Sammy how the angles were explained to me is the gearbox output shaft and the pinion should run on a paralell plane and when the tailshaft is in it should have a 3 degree max. angle on each end. The tail shaft, pinion and output shaft should not be in a straight line or it won't work.

The problem I'm still having is the pinion is still on a different angle to the output shaft.

Mal,
All these theorys and many have varied opinions! are great in a real world, but there pretty hard to achieve, the basics are there but the fine tuning as such is not often mentioned. Pinion angles vary greatly and others are straight. Angle increases are determined by what suspension setup vehicles run.
Nearly every Subaru running uni joint shafts are straight, from output shaft to diff flange. So very Minimal angle is being applied.
Nissan X trail is another, straight as well.......... With both these vehicles having fantastic service life on there unis and no vibration. Go figure!
Harko and Sammy are right in what they have mentioned as to being good pinion angles..........
When checking angles, the advise you have been given is pretty well right in what there saying, the other allowance which is not mentioned, is the sideways pinion angle.
Most set ups are not straight down the line, looking directly above or over the drive line. With this you will already have a pinion angle increase over what the horizontal measurement is. Ideally if possible is to have the output shaft and pinion angle dead straight, and this is the best method, but motor fitments and gearbox positions do not allow for such installations.
To check these is pretty easy.
Find a level surface and Jack your car up on stands and do a drop or plumb test. Start from the centre line of the Harmonic balancer, and with a plumb bob mark that position on the ground. Then take another reading from the gearbox output shaft, mark that spot and do a final at the diff pinion and mark that position. You will have these marks layed out on the floor, you can now tell 100% where the centre line alignment is, and how far out it actually is. These angles also have to included into the calculations.

There are lots of other factors that come into play, like how far does the diff move, how much do the springs move, are tramp rods fitted. Is it leaf or 4 link etc;
On a different note:

I think you should try to move the Convertor to another position on the ringear, and see if the vibration changes at all. Code 85 often comes up in a limp code and that can be the cause of the convertor itself, with the transmission temps on the upper and slipping. We have replace a few convertors with shudder and vibrations problems and they throw code that comes up everynow and again. Just go over all your grounds and make sure that there all there, with clean connections. A lot of the grounds for the gearbox and engine run through the main wiring loom and go through the BCM and ABS units, and because you have deleted those components, maybe missing a few vital ground connections. Just a thought.
The simplist of things are the biggest annoyenses.

Regards John

I'm very much impressed with your reply, John............

frats,
Rosco

So am I,

Today I put it back up on blocks to the correct ride height, and carefully measured all the angles again. At the correct ride height the tailshaft is spot one parallel with the floor with the engine and trans running at 3.5 degrees down at the rear, then the diff pinion is at 2.5 degrees down at the front. So according to what the experts have told me I should be close to being right.
One thing I did find was the rear uni joint was stuffed. Turns out I over tightened it causing it to bind up and mark the cross. Got a good 300k out of that one.
Anyway I ended up lifting the rear of the box aprox 7mm, giving me 3 degrees at the front with 2 at the rear. Put it all back together with a new rear uni and took it for a drive.
It was like driving a totally different car.
Now I have no vibration until about 110/120kmph, there it just starts to get a slight vibration.
Over the weekend I will play a bit more with the angle on the diff as I think it could come back a bit to allow for wind up under power.
I will also do a check on the straight down the line angle of engine, trans to diff with the plumbob as you said John. If this is slightly off set I should be able to reduce the gearbox and pinion angles a bit more.

Anyway thanks again for all your assistance guys.

Hi Guys.

I've done more than my fair share of gearbox & diff conversions over the years, so I will give you my take on it.

The centre line of the engine/trans should be parallel to the diff pinion. Not in-line with but parallel. This means that the 2 uni joints will be working thru equal, but opposite angles. This is the important bit, the angles must be close to equal. This means that if the eng/trans centreline is 4˚ down then the diff pinion should be pointing 4˚ up. Most eng/trans centrelines point down, but if they were dead level, the diff pinion should also be close to level.

But, & it's a big but. Because the diff changes angle during acceleration & deceleration, it must have some preload. What that means is that you point it down a bit lower than the 4˚up position, so when you accelerate it moves up to that 'sweet' point. This is why a drag car has its diff pinion pointing down, whereas a normal street car has it more up.

Hope this helps.
Dr Terry.

As I have said both pinion and trans are pointing down within the 6 degrees that I've been told is allowable. I still have a vibration, so as I now have a bit of time up my sleeve before YAMBA I'm going to wedge up the diff and try the parallel set up and see if this works better than what I have now.

yeah i reckon thats what you need to do Mal ...

Mal,
Ive been talking to my diff Guru and he tells me that the stock pinion angle is 6 degrees in the old holdens. He suggests an angle of approx 5 to 5 1/2 degrees for the 9 inch because the pinion sits lower.
I talked to him about vibration and he tells me it will happen from 30km/h
throughout the speed range usually from uni bind.
You haven't got this and have a vibration at 100km/h, this sounds like a balance issue of some description (tail shaft wheels and tyres or even as john says torque converter).
If you wedge the diff and nothing changes then it does look like just that.

Hope this helps.

Regards Greg

Thanks guys your input has been very helpful.

Cheers

i'm starting to get the impression you now have to much information

I was told by some that if the diff and trans were both pointing down, but at the same angle and not being more than 6 degrees than this would work OK, well I've tried that and it doesn't work. Well not for me anyway, maybe I'm holding my mouth wrong or something.
So this is what I'm trying for, the lower of the diagrams. Only mine isn't on such a big angle as the one in the picture and the back of my trans is pointing down and the diff is pointing up at the same parallel angle.

Mal,
Why is it that 99% of engines and gear boxes point down at the rear?
How many manifolds do you see taller at the back than front? This is to compensate for the angle of the engine in almost every car.
My stude has the motor down at the rear and the tail shaft level with the pinion of the diff ( no vibration ).
The unis should take up any angle as long as its not more than 6 degrees either way.
Yes Parallel is the ultimate but not always necessary.
Im still convinced its something else causing the vibration.
Check the shaft again make sure the uni weld yolks are opposite to each other eg north south at one end east west at the other (very common mistake).
Sorry can't help with anything else, I know its frustrating but you will find it eventually.
Regards Greg

G'day Malcolm,

I've just got back from holidays and have lots of forum reading to catch up on.Haven't read much of the replies to your current vibration problem but I'd be more inclined to agree with what EK 283 has just said.

Most cars are forgiving to some extent if diff pinion angles are out ( unless there is a big pinion angle variation from stock that is)and the uni joints do their job as they were intended to do.

However, if the tailshaft has been modified and the uni joint yokes on the shaft aren't welded exactly right ( as EK 283 said) then that leaves an area for vibration.

Dunno if your shaft is a new one or used one but used shafts can also bend and twist especially if they are subjected to excessive horsepower and abuse in previous years.

Example:- I fitted 350 Chev, T400 to my HQ GTS coupe years ago and had a local machine shop cut and shut the tailshaft to suit.

Bad vibration

Seems the unis were welded a poofteenth of an inch out of alignment

Rewelded the yokes correctly in position and problem was solved

Still had very slight vibration which was a balance problem.Eventually took the shaft to a tailshaft manufacturer in Newcastle and had it balanced.Seems it had a slight bend in it as well and was straightened by them while I was there.

No vibes at all then.

Hope this info helps,may not be your problem, but you have got to check all possibilities.

Terry.

my stock unmodified HQ vibrates i,m guessing balance or bend as when first driven smooth as silk, to find that it had BADLY worn front uni and yolk was even cracked, fixed these probs and now i have a vibration

EK283 wrote:Mal,
Why is it that 99% of engines and gear boxes point down at the rear?
Check the shaft again make sure the uni weld yolks are opposite to each other eg north south at one end east west at the other (very common mistake).

To allow for better coolant and less steam pocketing in the flow of the cooling system? Most front wheel drives even point downward for this reason.
Another maybe:
To allow the engine to jam under the firewall in the event of a collision, instead of throught it.

As Greg has mentioned the phasing of the flanges is important, but I do not believe it is super nesessary, so long as the shaft has been balanced well.
I have noted that nearly every Commodore that I have seen and worked on, has had out of phase flanges, by nearly 2 splines. Possibly the fitment of the centre CV joint and centre bearing has something to with that, to reduce the vibration!
I have even tried to line the phasing up on the joints only to make matters worse.


Mal................................................
An you could try is to use a mag wheel stick on weight and stick it on any position on the shaft, and note whether it is worse or improves, (Make sure you use a cable tie also or it will fly off.) if there is no change, its in another area and not your drive line positioning or angles.

Regards John