Drive line issues - need some ideas

[mjhcobra]

Hi Guys,

I backed my cobra out of the garage for the first time and felt, what I believe was the u-joints binding as I backed up. I have read that the drive line is to be about 3 degrees or so, but mine appears to be excessive. I have the car blocked up evenly on a level slab since my lift lifts the frame.

Included are the pictures of the car, joints, and drive shaft.

I have a 428, toploader, and 9". All mounts were welded in by Everett-Morrison.

Really cannot figure out where the bust is here. I think the yoke out of the trans needs to have more room for the u-joint to rotate-just looks to close and little room due to angle of drive shaft.
Any thoughts would be helpful. I have waited a long time to get this car out of the garage and on the road.
Martin

[frdfver]

Before you get too involved or worried about the drive angles I would pull the driveshaft and check the u joints for binding and free rotation. Also what type off locker or limited slip do you have. Some will feel as though there is a bind at slow speeds. The shaft angles are a little big but there is a lot more to it than just saying they should be 3 degrees. Lots of web sites that explain shaft angles and how to set them up. Its a great feeling getting that close to be driving....

Paul T.

[Jaydee]

It's not the angle of the drive shaft that's important, but the angle between the shafts themselves. Zero your gauge on the output shaft of the gearbox, then measure the angle of the diff flange. The difference shouldn't be more the 1.5 degrees. Google driveline phasing.
JD

[bobcowan]

Pinion angle is often misunderstood. Of you do a google search, you'll find some really great articles with pictures to explain it all really well.

But, there is one key point to setting pinion angle, and I think this is the most important point. The pinion is the input shaft of the differential. You want that angle to be about 1.5* downward compared to the transmission output shaft angle. Not the horizon. This is the key point. Not the horizon.

U-joint angle also plays a part here. And that's important for us because the drive shaft is so short. Ideally, the U-joint angle should be 0.5-3.5*. Some U-joints made for off roading can take more, though.

Your drive shaft looks to be about 8-9*. Usually the engine and transmission angle (AKA Power Angle) is about 5*, pointing down in the back. If that's true, then you're probably pretty close.

The picture looks like a lot more than 3*. But pictures can be deceiving, so you just have to measure and do the math.

[mjhcobra]

My pinion was set to the EM specs which is 0 degrees. I still believe my issue is my trans yoke. I reviewed my receipt and the yoke is a 1310 series which is the narrow slip yoke.the drive shaft end of the transmission end is narrower than the other end by about a 1/2". Since the u-joints bind here at the trans, I think I should replace the slip yoke at the trans to the 1330 or 1350 series which might at least allow it to rotate without binding. The 1350 yoke appears to be more dished than mine (see picture) and is a stronger unit. After I get it to rotate freely, I will do the measurements and math.

Which u-joints and tube size are the norm?

Comments???

I will post a pic of the drive shaft shortly.

[mjhcobra]

Here is a shot of the drive shaft. Notice the area that binds and the slight angle that required for it to bind.

[brandx]

Just a thought, but did you spin then drive line with it in the air and watch what was going on?

[mjhcobra]

In the air on the frame lift, it binds really bad. I almost could not get the drive shaft out. I had to remove it over the diff.

On the ground it pops (minor bind) but will roll.

[CHANMADD]

The middle pic looks like the front and rear yokes are not exactly inline.....if they're out the shaft will bind..
....

[CHANMADD]

You can't have any part of one part touching the other.....

[frdfver]

Does look like you have some mismatched parts. Hard to tell from the pictures the real problem-solution. Yokes will usually pivot a little more than that. I have seen some that have a small cut out in the trans yoke where yours is contacting the shaft yoke. My idea, suggestion to you would be to take it down to your driveshaft shop for their thoughts.

Paul T.

[mjhcobra]

The drive shaft is in the truck. We shall see what the experts say at the drive line shop today.

[mjhcobra]

I met with one of the local drive line specialists today and his comment was simple, kick up the pinion angle as much as possible to get the drive shaft close to level. With the 5 bar link rear axle, this should be fairly easy.
I listened for an hour and saw every type of yoke available. He did point out that I had the long, not short, yoke at the diff (2" +/- difference), which would add length to the drive shaft if I wanted to build a new drive shaft. I also have the smaller u-joints at the trans. Yokes are designed for different angles, the more angle, the bigger they are. The trans yoke is the smallest angle, probably why it is binding.

However, if I was to use a bigger joint with more angle to eliminate the bind, he said it would vibrate like crazy.

Bottom line-the shaft needs to be close to level. Since the trans has no adjustment, it must come out of the pinion. We shall see tonight.

[Jerry Clayton]

Is your rear IRS or live solid axle????????

since you may toss the front slip joint---why don't you grind some clearance in it to check out the results???????

[mjhcobra]

It is tempting to grind away, but the drive line guy said I would be in for a really rough ride.

I have the 5 bar link with the 9" rear.

I am hoping that adjusting the pinion up will get the shaft closer to level. At this point, any adjustment up will be an improvement.

[DanEC]

Maybe I missed it in all the above posts but the angle of the driveshaft is only one small part of the equation. What you need to know is the angle from horizontal of the differential pinion shaft/yoke saddle. Then you need to measure the angle from horizontal of the transmission output shaft/yoke saddle. This can usually be determined by rotating the yoke to top dead center and put an angle finder on top of it. I've had to sometimes put a big socket on top of the yoke saddle and the angle finder on top of that.

At normal ride height you want those two angles to be as close to the same as possible, regardless for the moment of the difference in height. In other words if the differential is angled down to the front 2 degrees and the transmission yoke is angled down to the front 2 degrees then that is what you want. If the differential is 3 degrees up to the front and the transmission is 3 degrees down to the front, you will have vibration problems. Then the difference in angle of the driveshaft needs to be measured and the resultant angles between it and the differential pinion and then betwee the driveshaft and the transmission shaft determined.

I know that at least a couple of degrees minimum (between driveshaft and pinion and driveshaft and transmission) is required in order to generate proper rotation of the needle bearings. I don't remember what an approximate maximum angle difference is - probably depends on U-joints, yoke knuckle clearances, etc.

Getting the driveshaft more level isn't the issue. Getting the pinion and transmission output shaft angles as close to the same as possible at ride height is what's important.

[frdfver]

The driveshaft specialist you talked with may know how to weld shafts together but I believe he gave you some bad info on driveshaft angles. I defiantly wouldn’t set the driveshaft level with all the adjustment coming out of the pinion. As stated by Dan and Jerry you need to check the angles on both the trans and pinion and work from there. As stated before there are a lot of trans yokes out there, mine included that have clearance reliefs in them. Link below to a simplified way to set up. Set up the angles then see if it still binds, grind clearance reliefs in it and if it vibrates take it out and have it balanced.

Drive Shaft Harmonics

Paul T.

[mjhcobra]

I have put an angle finder on both the pinion and the trans and both are about zero degrees. So herein is my problem-I cannot lower the trans without seeing the sidepipes drop. The only adjustable option is the pinion. I considered shorter springs on the rear to raise the rear axle, but then the tires will hit the fenders.

The "specialist" said that I could dish out the yoke for clearance, but he guaranteed tremendous vibration unless I can get the drive shaft "closer to level" (his terms). Keep in mind that both angles are close to zero degrees, so they are in the proper relationship with each other-there is just to much height difference with this short little drive shaft.

Everything I have done is by the numbers per EM's manual. EM even welded the brackets on the rear end as well as all the mounts on the frame.

Unfortunately, there are not many EM owners that have the same set up as I do that can offer help.

I almost lowered the trans mount 1.5" this weekend, then I noticed what it did to the sidepipes. I tried to loosen all the sidepipe bolts for max "lift" but this did not work.

I have actually considered a CV joint, but only a thought.

Using the shorter pinion yoke would help a little, but then I need a new drive shaft.

You would think that there is something obvious wrong here, but it just isn't obvious yet.

Thanks for the continued ideas-but with the trans mount "fixed", my options are limited.

Martin

[Jerry Clayton]

My EM has the C4 IRS under it ---on your 5 link rear does the 5th link locate the housing side to side????? if so you need to adjust it to center / line the pinion with the trans output shaft as the side angle combined with the vertical angle gets nasty---------

And the housing will probably rotate with the up/dowm travel of the housing in addition to any torque twist on accer/deceleration and or hard braking (twist the housing)

[frdfver]

The Zero degree reading at the trans seems unusual as most engines slant more than that, usually around 3 degrees. Unusual problem. Could always raise the front of the engine at the mounts to tip the trans down, then bring the pinion up to within the 1 degree or so difference, if you have the room body to header clearance, but maybe you already considered that...