Thread: LS1/4L60E/C4 Differential Alignment?

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I got the C4 rear in four boxes yesterday. I just got finished putting it back together and mocking it up under the frame. I have a question. I know that typically you are suppose to have a slight angle to a driveshaft going into a rear end. Does that really matter on these as the differential is in a fixed position? I'm wondering if it can be near straight or angled up toward the rearend from the transmission? My trouble is....My transmission snout is going to be much lower than the pinion on the rear end. I'd rather not have to lose floor space by raising the transmission. Will it matter if I have to angle the driveshaft up to the rearend instead of vise-versa? Also....I saw where someone made a comment on the forum, that the propeller shafts need to be angled slightly down. What about angled slightly up as long as I have plenty of travel for the coil-overs? Any idea just how much travel I should allow for? I'm using Aldan's for the front and most likely will use the same for the rear.

How about putting up a pic or two of what you have mocked up???? Easier then trying to visualize everything.....

Originally Posted by Dave Severson

How about putting up a pic or two of what you have mocked up???? Easier then trying to visualize everything.....

I'll do that Dave. It'll have to wait till morning. The little lady says its time to watch a movie now. Every now and then I can sneak in here and check out the forum without getting to much grief.

Dave

You want the centerline axis of the rear-end input shaft to be parallel to the centerline axis of the transmission output shaft. The transmission doesn't need to point directly at the rear end input shaft.

By placing the centerlines of the rear-end and the transmission parallel to each other, the front u-joint will have the same angle as the rear u-joint. This will provide the least amount of torsional vibration in the drivetrain, and the quietest ride.

Originally Posted by Hot Rod Roy

You want the centerline axis of the rear-end input shaft to be parallel to the centerline axis of the transmission output shaft. The transmission doesn't need to point directly at the rear end input shaft.

By placing the centerlines of the rear-end and the transmission parallel to each other, the front u-joint will have the same angle as the rear u-joint. This will provide the least amount of torsional vibration in the drivetrain, and the quietest ride.

Thanks. I understand cancelling out the angle from one end to the other...no problem there. I'm wondering, and it'll probably sound foolish, will it make any difference if I am angled up (plan on keeping motor low and rear high) versus the normal angling down. I dont figure it makes any difference but I wanted to be sure before committing to something. Also, I would assume that the same would apply on the propeller shafts on the IRS. They may be angled up from the differential to the hubs. Man....I'm sweating this thing. I don't want to lose floor space and I have plenty of room to drop the motor even more. LOL's.

Dave

Match the down angle of the transmission output shaft with an equal, but upward angle of the pinion shaft.

This LINK should help.

If the output shaft of the trans is lower than the input shaft of the diff, and the driveshaft slopes upwards (instead of downwards), that shouldn't be a problem; however, you have to watch maximum angles. The rule of thumb is to divide driveshaft length by 5 to get the maximum angle. I don't like more than 6* total.

You will find that others have different ideas . . .

I ran into a similar problem many years ago, shaft angle reversed, when I stuffed a BB Rat into an 90'' A- Altered Sunbeam(was factory 86''),,, ladder bars held my rear end in place like yours and taking a chance, everything worked great. The trick is 'NOT' to have your prop shaft coming straight in, as this would have a tendecy to make the rotating shaft mass orbit,,,, good luck

Originally Posted by Stovebolter

I got the C4 rear in four boxes yesterday. I just got finished putting it back together and mocking it up under the frame. I have a question. I know that typically you are suppose to have a slight angle to a driveshaft going into a rear end. Does that really matter on these as the differential is in a fixed position? I'm wondering if it can be near straight or angled up toward the rearend from the transmission? My trouble is....My transmission snout is going to be much lower than the pinion on the rear end. I'd rather not have to lose floor space by raising the transmission. Will it matter if I have to angle the driveshaft up to the rearend instead of vise-versa? Also....I saw where someone made a comment on the forum, that the propeller shafts need to be angled slightly down. What about angled slightly up as long as I have plenty of travel for the coil-overs? Any idea just how much travel I should allow for? I'm using Aldan's for the front and most likely will use the same for the rear.

I finally got a few pictures. Looks like the output shaft on the transmission will be 12.25 inches from ground (pan clearance at 7 inches). Since I'll be using 27 inch tires my hub center will be 13.5 inches from ground, and the pinion appears to be in the same line as the half shaft outputs so it will need to be slightly higher. I'm going to say.....14 inches? With 36 inches from the rotating point on either end of the drive shaft, that should leave me with a 2.8 degree angle difference (drive shaft will angle up to the differential from the output shaft on the transmission). Looks like I'm going to lose a little bed depth so I can raise the frame rails up to give enough clearance for suspension travel? I might do a recess box where the rearend resides. I've seen it on a couple web sites....like Progressive Automotives site. Tell me what you thinks guys?

Thanks,
Dave

I only have one pic showing up????

Anyway, not saying there's anything wrong with a driveshaft having the angle bass ackwards, just never have dealt with it before.. With it being a solid mount center, as long as the pinion angle is correct it should work ok.... You're tranny and engine must be really low!!!! No clearance issues with them?????

Ok. Try em now. I tried loading direct from my flickr account...the pics must have been too big so it was taking me a while to convert them. I have 7 inches of transmission pan clearance. I could raise the engine/tranny but I'm trying to avoid losing the floor space to a huge transmission hump. They should all be up now.

Dave

Pics came thru fine this time.... I guess if the angles come out correct on the tailshaft and pinion it should be fine.... With the center section mounted as you have spec'd, what angle will your half shafts be at?????

Originally Posted by Dave Severson

Pics came thru fine this time.... I guess if the angles come out correct on the tailshaft and pinion it should be fine.... With the center section mounted as you have spec'd, what angle will your half shafts be at?????

Dave,

With the center section mounted where it is now wont give me any susplension travel. I'll have to raise it a couple inches. Still trying to figure out me options. I'm told the half shafts need to be sloped downward slightly instead of upwards. Still digging for that info.

Thanks,
Dave

Dave,

More imprtant than height from ground is the angle. Get the chassis level, then get an angle finder, they sell for less than $10 at Harbor Freight or Sears and place it against the transmission output shaft. Ideal down angle is 3-5 degrees. Then measure the angle on the input shaft (pinion angle) of the differential center section. The angles should be similar but opposite. In other words, if the transmission shaft angle is 3 degrees down, the input shaft should be 3 degrees up. That will make them parallel. In live rear ends people will put some down angle in the pinion to allow for the rear end to twist up under torque. That is not an issue for you since yours will be solid mounted. The drive shaft angle should follow the guidelines mentioned by Jack.

hope that helps

Pat

Originally Posted by Stu Cool

Dave,

More imprtant than height from ground is the angle. Get the chassis level, then get an angle finder, they sell for less than $10 at Harbor Freight or Sears and place it against the transmission output shaft. Ideal down angle is 3-5 degrees. Then measure the angle on the input shaft (pinion angle) of the differential center section. The angles should be similar but opposite. In other words, if the transmission shaft angle is 3 degrees down, the input shaft should be 3 degrees up. That will make them parallel. In live rear ends people will put some down angle in the pinion to allow for the rear end to twist up under torque. That is not an issue for you since yours will be solid mounted. The drive shaft angle should follow the guidelines mentioned by Jack.

hope that helps

Pat

Thanks. I've got that part figured out now, with an old chassis book and helpful information from everyone on here, but there was nothing in the book about the C4 IRS. Now I'm worried about how much angle....if any....I need for the half shafts.

Thanks,
Dave

Tha