conversion and keep driveline straight

[Guest SpyderZ]

I am gathering information for my LS1 swap. For the guys who'd done any V8 conversion what did you do to keep the driveline truely straight? Here is the problem I have. This is what I wanted to do: I wanted to make measurements of the stock driveline in relative to various points of the body before removing the stock driveline. Then when I put the new driveline in make the same measurements and adjust from there. The problem I have is I bought the Zcar with out the stock driveline in it. How can I make my new driveline (LS1) as straight as possible? Thanks for any info.

[Tim240z]

When I mocked mine up, I had my machinist build me a solid driveshaft (no universal joints). Then, I slid it into the tranny and lined everything up. A bit extreme, but leaves nothing to chance.

[Guest SpyderZ]

That should work. I will give that a thought.

[LS1 Z]

Are you making your own mounts or using John's Kit? What I'm getting at is I'm using Johns and I'm not having any issues.

JOEY

[pparaska]

Actually, you want to have SOME angle in the u-joints, at least 1/2 degree:

 

http://www.vibratesoftware.com/html_help/html/Diagnosis/Propshaft/Propshaft_Angles.htm

"The working angles themselves should not equal zero. This is because with a zero working angle, the needle bearings within a U-joint will not rotate causing brinelling and premature wear of the U-joint."

Using the solid driveshaft to set up the driveline angles may not be the best way to go.

[Tim240z]

Pete,

Even with the solid driveshaft, it is almost impossible to get it 100% straight due to rubber mount settling, bolt hole shifting etc.

I had my Z up to ~90MPH and never had the slightest vibration, and I know it wasn't perfectly straight, but I know it wasn't far outta whack....

[pparaska]

Good point. I found another site that recommends at least 1 degree of running u-joint angle:

http://www.drivelinesnw.com/troubleshooting_symptom.html

[DaleMX]

Transmission and diff should have the same angle. If one is different then driveshaft will vibrate ( the driveshaft oscillates from the front to the back). You will always get a little since the angles change when torque is applied. Look at some of the wild angles you see on 4X4's. Just get them equal. On the Sebring I was working on the differential was about 6" offset to the passenger side, but if the angles on the transmission and the differential are the same then no vibration will result (within reason).

[VinhZXT]

Joey,

I have not been up to date with all the info on this site about the LS1 conversion. I will check out John's mounts.

Pete,

I said "truely straigth" but I know it's impossible to make it straight like an arrow due to many other factors like Tim said. I just want to understand the techniques you guys used and I will do my owe evaluation to which one to use so I can get the driveline straight as possible to minimize vibrations. I have not seen many of the V8 guys talked about this and I was just curious about that. Thanks for the info guys...

[pparaska]

Vinh, if you haven't read this page, you might want to review it:

http://alteredz.com/drivelinemods.htm

 

The tool I used to measure the vertical u-joint angles look like these:

http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=3254&prmenbr=361

http://www.mcmaster.com/ctlg/DisplCtlgPage.asp?ReqTyp=CATALOG&CtlgPgNbr=2104 under "General Purpose Angle Indicators"

 

Measure under the driveshaft as installed and then the block (like the starter mounting surface or pan rail or front machined surface) to get the front u-joint angle, then under the driveshaft again and the differential housing to get the rear angle.

 

The horizontal angle is more difficult to measure, as you need to do some measurings in the lateral plane under the car and do some drawings and use some trigonometry. But I seem to recall that this was less than 1 degree on my car. Anyway, the total angle is the RSS of the two angles (square root of the sum of the vertical angle squared and the horizontal angle squared). Get that angle in the 1 degree range (and equal front and rear of course) and you'll be in happy land.

[Pop N Wood]

I have not seen many of the V8 guys talked about this and I was just curious about that. Thanks for the info guys...

 

Driveline vibrations get talked about here quite often. Z's are slightly more prone to vibrations from an incorrectly set up drive line due to the relatively short drive shaft and the generally higher shaft RPM's caused by the lower rear end ratios commonly found with Z’s.

 

Ron Tyler had a whole section about driveline vibrations (can't find the link to his site). He was a strong advocate of aluminum driveshafts. He attributed the lack of vibration in his V8Z to the lower rotating mass of the aluminum shaft.

 

What you really need to do is draw an imaginary line straight out of the transmission output shaft and diff shaft, then adjust the trans/diff mount points to keep those two lines parallel. This will guarantee the same U joint angle in the front and back joints. U joints don’t actually rotate at a constant speed (unlike CV joints, hence the name). Keeping them at the same angle keeps them in synch and harmonic vibrations to a minimum.

 

I have always been wary about aligning the shafts with angle indicators because for one thing angles are generally hard to measure with any accuracy, but mostly because putting an angle indicator on the side of the transmission is no guarantee it is parallel with the output shaft. I guess the idea works because enough guys do it that way.

 

IMO the solid drive shaft is good because you can see the exact axis of rotation of the output shaft. Just need something similar on the diff shaft and aligning the two would be a 10-minute job.

 

I came up with the idea of using laser pointers and two sheets of paper. One guy actually did it that way (and posted how he did it). Spinning the shafts with the laser pointers attached guarantees the exact centerline of the output shafts are know. It is then just a matter of ensuring the two laser lines drop down and over by the same amount in the front and back (hence the paper). When that happens the shafts are parallel in 2 dimensions.

[VinhZXT]

Great information guys.. Thank you very much for your time. I am sure when it's time for me to do this task I will be asking more questions. Thanks again.

[pparaska]

I LOVE the idea of using the laser pointers! Great Idea!!!

[Dan Juday]

I have a Ron Tyler front diff mount that makes adjusting the pinion angle much easier in a V8 Z. Check his site and a search here for pics and info.

 

Also, I can attest to the aluminum driveshaft helping as well. Mine came out of an '84 Vette and includes something like a harmonic balancer on the tranny yoke.