4 Speed drive line orientation?

[Bud English]

Hi all -

Here?s where I should have taken more pictures during my tear down or at least paid closer attention.

As I?m trial fitting things back together, it looks like the drive shaft runs from above center at the front of the chassis to well below center and to the right at the diff. It also looks like the crank centerline runs uphill slightly front to back. So, all in all, uphill from the front of the motor to the front universal joint, then down hill and to the right going back to the rear universal joint, then leveling off and back to inline with the chassis through the diff.

Can this possibly be correct? How close to a straight line should the relationship of the crankshaft centerline, the drive shaft and the diff input shaft be? Also how does the drive shaft position relate to the center line of the chassis?

I know that the pinion centerline is offset from center in the diff. So the off center left to right situation doesn?t concern me like motor centerline to drive shaft centerline mismatch does. I also know that with a ?fixed? motor, transmission, and diff location the universal joints don?t get near the workout than they would in a car with an un-sprung diff. I?ll also admit that this is a Zetec mod (no hating, please). Having to lower the taller engine will add to the driveline mismatch. I just need to know the stock orientation for a starting reference.

Can anyone with a built up chassis and the body off, have a look, and answer my questions?

Thanks -

[elj221c]

Can this possibly be correct? How close to a straight line should the relationship of the crankshaft centerline, the drive shaft and the diff input shaft be?

Thanks -

Can't remember where but I have read/heard that , even if it could be done to get it all dead in line, it shouldn't be so. Pretty sure there should be a slight down hill from front to back on the engine/gearbox, though.
Not likely to happen with rubber mounts and Lotus chassis anyway!

[Bud English]

Hi Roy,

Thanks for your reply. I'm not paranoid; I just want to do this right the first time. What you say makes sense. I?ll just make sure the diff and motor are level and not worry too much about the subtle drive shaft angle.

Your input and information received from another source have put my mind at ease. Now I?ll head for the garage and see to that gaping hole in my front cross member.

Thanks,

[holywood3645]

Bud, that the same way the propshaft is on my S4. The body is off and engine, gearbox, diff, and pror installed. It does look weird, and i thought the same when I put them together.
James

[stugilmour]

Bud, there were some posts on this issue that I found helpful when I was doing my car.

My understanding from the advice from folks here that are more knowledgeable than me was that as long as the flange faces at each end of the prop shaft are at the same angle / orientation, the universal joints work correctly. If the angles are significantly different, the joints become unstable. I sort of imagined the prop shaft centre describing a circle during rotation rather than it spinning on it's true centre. If I understood the advice correctly (probably a big IF ), it is OK if the flange angles at each end are not vertical, just that they have to be the same angle from vertical. The prop shaft universals were called a 'Hooke Joint', and apparently the flange angle is a standard issue / feature of this design. Not being a mechanical engineer, I don't know how this issue is mitigated in a live axle design, but it might not matter if the diff is going up and down vertically and the diff flange is exactly vertical? I understood the CV design gets around this issue, hence it's use on the two rear driveshafts on independent suspension designs.

http://en.wikipedia.org/wiki/Universal_joint has a section called 'Double Cardan Shaft' that seems to describe the prop shaft.

With the MT75 in my car I had to adjust the motor mounts and transmission mount heights to maintain a vertical orientation of the transmission output flange to match the diff flange. In my case the Spyder type motor mounts for the TC required minor adjustment downward for bonnet clearance first (apparently quite common and not a big deal), followed by adjustment of the Spyder supplied transmission mount to get the output flange orientation correct. Maybe a fluke, but it all worked out and the drive train is smooth in use. So I think the key is to sort your Zetec engine mount first, then the transmission mount may need fettling.

HTH Interesting topic even if I don't fully understand it. Corrections welcome.

[garyeanderson]

The spacers are 7/16 inch thick on an Elan, I am making an assumption that they are the same on a Plus2. See part labeled "8"

Gary

[Bud English]

Thanks for your help on this, Gary. Good to see you back.
The parts lists posted on the R.D. site show the same part number for both cars. Anybody see a problem in leaving them out to lower the rear of the transmission? It looks like I'll need to do at least that to keep the driveline orientation correct and lower the engine enough to clear the bonnet. I'm not a fan of the "power bulge" approach.

[garyeanderson]

Leave them out if you have too, if it vibrates then put them in and slot the motor mounts to drop the engine. You should be able to use a round file on the engine mounts to get nearly an 1/8 of an inch and if thats not enough then do the same on the motor frame mounts. If I have to tell you how you should be doing any of it.

My guess this may not be a twin cam? if so please don't leave out this kind of detail as you will get advice that does not apply. all bets are off of any of this info applying at all.

elan-mods-f31/zetec-engine-lotus-chassis-t24502.html

[Bud English]

Yeah, I mentioned that it was a zetec install in the first post. I had my answers to the original driveline question thanks to you and others. I should have asked the transmission spacer question in the thread in the mods section. The motor mounts, I'll be building from scratch. I'll keep that in the mods section too.

Thanks again,

[garyeanderson]

missed it

sorry please disregard everything I have ever written

Gary