Help! Pinion / drivetrain angle

[Jim Wintz]

I am in the process of setting up my drivetrain in my Cobra. I have been researching information on pinion, drive shaft and drivetrain angle and still have a few questions I hope you guys can help with.

I am stting my engine at 3 degrees, with the tranny heading down. This seems to be pretty generic in everything I have read.

I am running an 8.8. IRS so I don't think a lot of the pinion angle information applies as the rear end will not roll like a leaf spring to 4 link type set up.

This is where my confusion starts.
Most state to have the rear end at a slight downward angle with the front of the rear end angled down to allow it to roll up under acceleration and hope to align closer to parallel with the tranny. Most state about 2 to 5 degrees with the front of the rear end angled down. With an IRS I did not think I would need this much, I was thinking about setting it at 1 degree down in front. This would result in the center of the tranny tail about 1/2 inch higher then the center of the rear, allowing for a slight downward angle of the driveshaft. My other confusion is in the information saying that the angle of the tranny and the rear end should be parallel but not intersecting. If I did this the front of the rear end at the yoke would be going up about 3 degrees. This does not agree with the info stating the front of the rear end should be angled down to allow for the slight roll.

I hope this makes sense, if anyone has any information or answers it sure will help me in attempting to get my drivetrain all aligned properly. Thanks in advance for all of the help and responce I hope to get.

Jim

[CowtownCobra]

Jim,

Can't answer your question, but don't forget the drive shaft safety hoop.

[Jim Wintz]

Dave,

Already got one, it came with my RUCC kit, thanks.

Jim

[shnookie]

Jim:
What did you do about axles? I'm thinking about having new ones made up as opposed to shortening mine. I also have an IRS RUCC car.

[xlr8or]

I believe one of the MFG sites had a tech article on pinion angle. It is important to get it right with such a short drive shaft even with the independant rear to avoid any binding in the U-joints. I'll look around and see if I can dig it up.

[hog]

Denny's Drive Shaft mentions in the FAQ's a little on drive shaft angle. http://www.dennysdriveshaft.com/html...%20application
Or the website at www.dennysdriveshaft.com
This may help you some.
hog

[Jim Wintz]

Shnookie,

My kit came with the axles, I believe they are shortened thunderbird axles. The appear to have been cut and welded.

All others, thanks for the info so far, I will look up the sites for information that you had mentioned.

Jim

[zipzip]

Here's an article in Street Rodder concerning angles. Hope it helps.
http://www.streetrodderweb.com/tech/0203sr_driving/

And another informative page:
http://4crawler.cruiserpages.com/4x4...line-101.shtml

Looks like close to parallel is the best. I'd say if you don't expect any pinion shaft movement (the diff case or mount might move under load a small amount), then set it up 2 deg to be close to parallel but leave some room for movement.

The pic courtesy of www.madxj.com

[strictlypersonl]

There actually may be some disadvantage to having things exactly in line. Because there's no rotation of the bearings in the joints, the needles and cups may tend to fatigue earlier than if there was some motion, spreading the load out a bit.

[Richard Hudgins]

Originally posted by strictlypersonl


There actually may be some disadvantage to having things exactly in line. Because there's no rotation of the bearings in the joints, the needles and cups may tend to fatigue earlier than if there was some motion, spreading the load out a bit.

Bob,

You are quite correct. You must have a offset in the shaft.

The best setup is parallel with a slight vertical or horizontal offset (2>5 degrees is recommended) as shown in the second image.

If the shaft is dead inline with no offset, you will rapidly brinell the bearings. The needle bearings need to move in the race.

[Jim Wintz]

Thanks guys for the info.

I did some shimming and adjusting and I can get pretty much anything with in reason. Going with the thought of keeping the engine and rear parallel I made the following adjustments.

Originally my rear end housing as angled about 5 degrees down in the front. The engine was about 3 degrees down in the back, this appeared to be a bad set up.

Now after some adjustments I still have the engine at 2.7 degrees with the tranny tail shaft going down. The rear end housing is now at 2.3 degrees with the front of the rear end where the drive shaft mounts going up. They are almost parallel, I might try to improve this a little. The difference in the center of the tranny and the rear end where the drive shaft will mount is about 1/16th, with the center of the rear end being higher. This means that the drive shaft would be running almost parallel, at no angle. However it would be running at about a 2.5 degree angle coming out of the tranny and then again going into the rear end where the u-joints connect. These angles would be almost the same but running opposite to help keep the u-joints lubed.

I was wondering if there were any thoughts on this set up, looks ok should work? Bad, need to change it ? ect.. ect.. From what I have read this looks like it should be ok, my only concern is with the rear end going up in the front 2.3 degrees will this hurt? With it being an IRS and the differencial being mounted almost solid to the chassis I did not think it would hurt or be effected when I accelerate like leaf spring or 4 bar type set ups.

Any thoughts and good advice more then welcome and I am sure would be helpful.

Jim

[craigayl]

Jim

Just as one more reference the following link is to an excellent article on driveline alignment and phasing. It also speaks to the need for off-set.

http://jniolon.clubfte.com/driveline...nephasing.html

Craig

[Steve Riley]

Thank God I logged on and was reviewing this thread. I'm at that stage of aligning the engine/trans-driveshaft-rearend assembly now, and now I know how it's supposed to be set up properly! Thanks to all of you.
Steve

[Jim Wintz]

Well, I did more thinking and then more changing.

I did not like having the front of the yoke pointing up to keep it parallel with the engine and tranny. My thought was that if there was any roll of the rear end housing the front of the yoke would go up further and possibly make the situation worse.

So what I did was I changed my engine and tranny angle to 2 degrees with the tranny going down. I then changed the rear end with the front of the yoke going down about .7 degrees, (almost one degree down). The center to center height from the tranny to the rear end is now 1/8 difference with the tranny being higher.

My thought is that this is a close combination of the different versions I have read about. One suggesting that both the tranny and rear end angles being the same but opposite, intersecting in the center of the drive shaft. My angles are pretty close to being with in 1 degree difference. Plus I think I am set pretty good if I get any rear end roll, say the rear end rolls up about 2 degrees or so, as I have read to set them anywhere from 3 to 7 degrees down to allow for this. Mine being an IRS should not roll that much, so I allowed for about a 2 degree roll. If this happens under acceleration give or take a degree I should then have the rear yoke pointing up 1 to 2 degrees under acceleration which then would have the rear end and engine / tranny running close to parallel. Which again I hear is a good set up.

Well now on to getting my driveshaft ordered and getting the car done so I can trial my theory on this set up. No matter what I feel they are set up pretty close and should not cause any serious issues.

PS: Also wanted to mention the the engine / tranny center to the rear end center is off set about 1/2 inch from side to side. Again I have read that this is also a good thing.

Thanks for the help. Anyone reviewing this please give me you input and thoughts on my set up. If I am way off base I would love to know sooner rather then later.

Jim

[Cobra20646]

Jim,

I too had serious concerns about drive shaft angle when I was completing my car after a tranny swap. Due to the very short drive shaft that I had to deal with, the 1/2 inch horizontal offset I had between tranny and pinion resulted in an angle of 7 degrees. The pinion and tranny are as close as I could get to being directly inline vertically. The rear is IRS like yours, and bolted to the frame, so I don't believe there is any roll to experience either under power or brakeing. Tom Wood, a very knowledgable guy assisted me with this set up and provided a drive shaft to span the short distance. I have noticed no vibration due to the angle, and after three years and about 8000 miles have noticed no abnormal wear to the U joints. In fact I just pulled them last week to inspect them again.

There are standards that we all try to achieve, but sometimes you just have to deal with what's on your plate. Go with your best plan, and evaluate your results. If you have to go back and change things, consider the whole thing an education

Good luck and don't loose too much sleep on tring to achieve the perfect angle.

- Jim -

[rwall49]

I was just wondering about this very subject tonite and thanks for the info. Helps me understand more about drivetrains especially in these cobra's.

[392cobra]

This one is a good one too.With our driveshafts being so short,the working angles get critical in a hurry.

http://www.drivetrain.com/driveline_angle_problem.html