Pinion Ange again

[rponfick]

I know these questions are like "what is the best oil to use", but there are us still curious out there.

Working on a Mk5, TKX, 347" BP, FFR 3 link.
My question is how much adjustment should you have on the 3 link upper link bar? I have about a max of 1/4", 5 threads showing, with the banana bar against the rear crossmember.
Both my tranny tail shaft and pinion shaft are -1 degree.
It would appear that I need to raise my pinion angle up to about +1 degree for my lines to be parallel. I don't think I want to put any more spacers under the tranny mount as the driveshaft angle then looks really steep.
I have tried the Tremec app with the full length of my adjustments and have not gotten any acceptable results.
Or, is a negative degree that bad for both readings on a street car?

[Presdough]

You dont want the shaft at zero degrees as the needle bearings in the joints will not rotate and longevity will suffer. 1-3 degrees is what you're looking for to give the joints something to do and with a shaft that short you will not have a vibration in any case.

[Jeff Kleiner]

Regarding your photo and comment that "the banana bar is against the rear crossmember." Since I haven't had my hands on a Mk5 with 3 link I can only speak to the Mk3 and Mk4 but with those if the bracket is touching the panhard bar bracket as you show it indicates that the top link is too long which results in the front of the pinion pointing up---which is NOT what we want. Once again---the front of the pinion needs to angle downward approximately 2 degrees IN RELATION TO THE TRANSMISSION OUTPUT. You know how they say that a picture is worth a thousand words? Hopefully this diagram that I made about 10 years ago will help clarify it for you.

https://thefactoryfiveforum.com/attachment.php?attachmentid=204763&d=1514586767

And remember, all of this is to be done at ride height.

Hope that helps!

Jeff

[rponfick]

Thanks Jeff, I have followed your posts and agree. The goal of parallel at 2 degrees difference is what I am aiming at. You indicate the top link is too long, and I tend to agree, but how do you shorten it enough to matter. It is currently at -1 degree. and taking up the few turns did not help much. Do I take out the link and cut some off the ends?
I am in the lower hole at the front attachment bracket, but in looking at it, changing to the upper hole would not appear to affect the length to the banana bracket.

On your ride height comment, I thought I had seen that what matters is the difference between the two numbers, and level did not matter, but I could be mistaken.

I will continue to cogitate.
Thanks, Ralph

[BornWestUSA]

It sounds like the trans needs more spacers.

I have 3/4" of spacers between the rear of the trans and the trans mount.

My upper three link "banana" is very close to the crossmember and almost as short as the rod adjustment will allow.

[CraigS]

You show at least 1/4" of available adjustment. Hopefully there is also 1/4" at the other end. That would allow you to shorten the link by an overall 1/2". Surely that will be enough.

[rich grsc]

I have noticed on several posts how close the 'banana' bracket is to the frame crossmember. That was not an issue on older builds where the owners installed the bracket to the axle. Are these brackets already on the axles when received, not installed in the correct position, a change in the bracket shape?

[rponfick]

I have noticed on several posts how close the 'banana' bracket is to the frame crossmember. That was not an issue on older builds where the owners installed the bracket to the axle. Are these brackets already on the axles when received, not installed in the correct position, a change in the bracket shape?

Rich, yes, the new rear ends from Moser and FFR have the banana bracket welded in place. Not like the older ones that you installed and maybe had some adjustment. Not sure about your second two questions.
Who know what type of jig Moser may use to weld the bracket on to FFR specs? Might be an interesting question.
Ralph

[Jeff Kleiner]

I have noticed on several posts how close the 'banana' bracket is to the frame crossmember. That was not an issue on older builds where the owners installed the bracket to the axle. Are these brackets already on the axles when received, not installed in the correct position, a change in the bracket shape?

Rich,
I've found the banana bracket either touching or very close to the panhard bar brace on quite a few cars that have come through my shop. On every single one the pinion angle was off, with the upper link set too long and front of the pinion pointing up. Every one. If you see a 3 link car with the rear wheels sitting far rearward in the wheel openings I can pretty much guarantee that the top of the bracket will be touching, or nearly touching, and the pinion angle will be wrong with the nose up.

Jeff

[rich grsc]

Yep Jeff, I'm well versed on the whole pinion angle thing :rolleyes:, to the point I just don't much care. It's really an easy thing to do. My comment was more to question whether the pre installed brackets are installed in the correct position ??

[rponfick]

I have moved my upper link so all threads are gone and against the jam nut, and the shaft should be at its shortest position, which should have the pinion down as much as possible. My Iphone reading is still about 0 degrees on the flat surface of the driveshaft mounting point on the front of the diff.

What is the upper hole in the front of the link bracket for? The manual does not give any indication of which hole to use, and I am in the lower hole.

I am about of the mind to bolt it all together and forget about it.

Ralph

[GoDadGo]

I had similar issues with getting the pinion angle perfected and my solution was something that most folks never consider.
Since I needed a custom driveshaft anyway, I decided to get a set of shortened lower control arms too.
My rear wheels are well centered and the angle of the pinion dangle is spot on perfect.
Taking this action does require you accurately determine your yoke penetration.

U-Joint Phasing Video:
https://youtu.be/Idk3BVDVHq4

Redbone Roadster Video:
https://youtu.be/iwslgKJUaKc

Spohn Performance Link:
https://www.spohn.net/shop/Factory-Five-Racing-MK3-MK4-Roadster/

Hope This Helps & Good Luck!

[Jeff Kleiner]

I have moved my upper link so all threads are gone and against the jam nut, and the shaft should be at its shortest position, which should have the pinion down as much as possible. My Iphone reading is still about 0 degrees on the flat surface of the driveshaft mounting point on the front of the diff.

What is the upper hole in the front of the link bracket for? The manual does not give any indication of which hole to use, and I am in the lower hole.

I am about of the mind to bolt it all together and forget about it.

Ralph

If you're showing zero degrees on the pinion then ideally we'd like to see the transmission output showing 2 degrees down front to rear...but if you have 1 degree down as indicated in post #1 just go for it.

Top hole in the front upper link mount improves roll center for better handling; lower hole improves straight line traction at the expense of handling. No free lunch you know ;)

Jeff

[rponfick]

Thanks Jeff. I wonder sometimes if we over-analyze this subject.
I looking at the car from the side, the pinion in a couple of inches below the tranny shaft, so even a zero degrees on both, they are not pointing in a straight line at each other, like the one spicer video shows. And, he u-joints are obviously flexing.
So, I will take your advice and just go for it. I don't changing to the upper front link mount hole will accomplish anything.
If there is vibration upon driving down the road, we may have revisit the issue.

Thanks, Ralph.

[rich grsc]

This subject is always 100% over-analyzed. They do not need to pointed at each other in a straight line. There are two u-joints so that the shaft can operated at an angle. They will safely operate at angles way beyond what is 'recommended' here without issue. You are good just as is

[rponfick]

This subject is always 100% over-analyzed. They do not need to pointed at each other in a straight line. There are two u-joints so that the shaft can operated at an angle. They will safely operate at angles way beyond what is 'recommended' here without issue. You are good just as is

Thanks Rich. That is sort of the reason I started the thread by asking "What is the best oil to use?"

I also wonder how many roadster builders have experienced or reported driveline vibration issues, regardless of adjusted religiously, or not.

Ralph

[Avalanche325]

I changed my rear ride height. I went on a long trip afterwards and was getting a vibration every time I lifted on the highway. That cost me a pinion bearing replacement. Definitely not a "don't worry about it" item.

[rich grsc]

Unless you change the height by several inches, that wasn't the cause

[CraigS]

The goal is to have the trans and the diff somewhere between parallel and the diff up to 2deg pointed down towards the front. The diff can be above, below, to the right or the left of the trans within some pretty wide limits of ujoint angularity. So changing ride height is well within those limitations.