FastKat

iTrader: (10)

I am doing an LS1 swap into a Jaguar XJ6. The Jag has a rear IRS, so the rear end is fixed to the chassis. Right now the input shaft of the rear end is sloped up about 1 to 1.5 degrees. What angle do I need the output shaft of the transmission to be at? Right now it is sloping down about 2.5 to 3 degrees, and I don’t want to bring it up any higher because I am running out of room in the trans tunnel. Is this close enough? Anything else I need to know?

Thanks, -Dave

Ted J

iTrader: (4)

I've read for race cars that 1 to 2 degree's is where you want to be and for a street car you can have the difference up to 3 degree's. Don't quote me on that though for I don't know how good my sources are. Does anybody know for sure on this and if the info I got was correct?

The stunningman

iTrader: (47)

That would be fine. Everything your messing with is locked. The rear being IRS isn't moving its fixed in the center. The engine being angled back is good you don't want the alignment straight in line. The u joints need to rotate at an angle. Most jag swaps carbed have more angle in them for engine mechanical reasons.

FastKat

iTrader: (10)

Thanks for the input guys. I just want to make I do this right the first time.

Keep it coming!

'JustDreamin'

With an IRS rear, which shouldn't move at all, the angles should be the same.

For most street cars with live axles, there is some rotational movement of the rear axle (especially with leaf springs), so to compensate for the movement under load, you cheat a little bit.

I think if you're within a degree or so, you should be ok. Much more than that and I'd be looking at moving one end or other (either trans or axle).


In an ideal world, the angles would be exactly the same, nothing would move, and there would be a small amount of offset (like 1/2" to 1" both vertically and across the car) so that the u-joint moved slightly to keep the grease moving and the rollers from constantly hitting the same spot. Since we don't live in an ideal world we do what we can and live with what we cannot fix....

'JustDreamin'

FastKat

iTrader: (10)

Yea I guess there are different schools of thoughts... some people say it has to be almost on the money, others say up to 3 degrees difference is okay...

RFERG43

The most important thing is that the axis of both be parallel. A small offset is good for the bearings.

'JustDreamin'

I'll share a quick story....

Used to work for a company that built television trucks. They built a truck on a UD chassis, with a 30 foot box (fairly heavy truck, GVWR was 25,500lb). Had a diesel and an Allision 5 speed auto. Truck was equipped with an aftermarket air ride suspension on the rear axle.

We brokered the truck when it was offered for sale by the original owner, and ended up selling it to a local cable / tv production company (with some rework). One of their first jobs was in Tennesee, and while travelling from Northern Va, the trans failed in Roanoke, Va. Shop there went and towed it recognized the truck as having been there before.

Turns out the previous owner put 7 transmissions in the truck (in 35,000 miles) before it was sold.

The transmission problem ultimately was caused by a pinion angle problem. Trans and all of the driveshaft sections (4 of them) ran at 2 degrees down. Rear was at 12 degrees. Total misalignment was 10 degrees. That is what caused 7 Allison automatics to fail.

Fixed the problem with appropriate shims and such, truck has never had another transmission problem (still running on number 8).

Obviously this is an example with some extremes, but does reflect what can go wrong.

'JustDreamin'

FastKat

iTrader: (10)

Which axis? vertical, horizontal? I think I'm looking for feedback on an acceptable margin of error.

'JustDreamin'

Hey FastKat...

The output shaft of the trans and the pinion should be parallel, in both planes. That would be horizontally (the angle we're usually concerned about), and lengthwise (looking top down at the trans / driveshaft / rearend). Most of us don't think of the lengthwise issue, but it is something to be concerned about nonetheless.

I'd say an acceptable margin of error is a degree or two max on the angle. And as far as the small offset, that is dependent upon u-joint angle. That'd be the angle that the u-joint flexes through. So, if the trans and rear are at 3 degrees down, and the driveshaft is level, the u-joint angle is 3 degrees, which probably close to the limit as far as a good number. Might be able to get a little further reliably.

I'd suggest doing some searches on the web for guys specializing in offroad driveshafts. Those guys push the envelope because of extreme offsets and high angles, and can tell you what the normal recommendations are and what you can get away with (sometimes with special hardware).

'JustDreamin'

Quick Double Nickel

iTrader: (5)

I found a short diagram on Street & Performance website:

Street & Performance

on the left hand side near the top labled "Drive Line Angles"

stealth71

iTrader: (15)

Here it is kinda crappy image wise, but it works.

stealth71

iTrader: (15)

Not to steal the thread. I am about to weld my crossmember back together and I wanted to verify this for myself and others. Where should we be measuring this angle from?

Some have stated the oil pan and other sources say on the transmission tail shaft. I want to make sure it is right before I weld it in place. It looks like aprox. 3* down is good on the motor.

Quick Double Nickel

iTrader: (5)

I always thought is was good to lay a piece of straight metal square tubing across the front valley rail and the rear valley rail on the top of the motor (what the intake manifold sits on). Then measure the angle by placing the gauge on top of that tubing.

FastKat

iTrader: (10)

Both the valley mating surface on the block and the tail shaft are good places to measure from. Some guys put the angle finder on the damper/crank pulley as well.

mramay

iTrader: (4)

My car on jackstands at the front, so there is a rather significant up angle on the whole thing. See if this sounds like it will work:
1. Per Quick Double Nickel - measure the engine once it's bolted in there (my conversion is in progress and the plastic LS1 is almost ready to bolt in with the new motor mounts.). Measure the plastic engine angle.
2. Use the same gauge to measure the car angle (frame rail??).
3. Stick a magnetic base for a dial indicator in the middle of the differential yoke and use the mag base shaft to measure the differentail angle.
4. Subtract angles to get differences.

Project GatTagO

iTrader: (7)

http://www.markwilliams.com/driveshafttech.aspx

Andrew

RFERG43

I got a small string level and marked the end pointing toward the engine and placed it on top the flat part of driveshaft front U joint and marked where the bubble was then did the same with the rear, keeping the mark pointing forward. The bubble should be very close to being in the same place.

redmist

Can't you use CV joints instead of u-joints? I understand they are ALOT more tolerant of misalignment. Audi and Bmw do this.

Andy1

I think there is more than one school of though on this. What's refered to as the optimum alighment leads to pre-mature U-joint wear, as the neelde bearings hob themselves into the yoke from lack of movement. Perhaps frequently replacing U-joints is prefered over vibration issues.

Andy1