I'm slowly working the kinks out of this build and one of the issues is the front driveshaft vibrates when going over 15mph.

Now the truck has a 5.5" spring over with HD OME 1.5" rear springs all around. The wheelbase has been lengthened 1.5" in the front.

The rear has a Trail Tough driveshaft extension and it doesn't vibrate at all.

In the front I have a double Cardon style driveshaft with a Trail Tough extension and a modified transmission crossmember.

I need to make new motor mounts because the original owner installed a twin cam gti and it's crooked. So I'm considering lowering the Engine, tranny, and tcase 2.5" to reduce the angle of the front shaft. I have plenty of clearance under the engine and header and the tcase has a Mighty Kong so it's protected. The slip joints in the driveshafts have plent of room so I'm not concerned with that either.

Does anyone see a problem with this that I'm missing? I'd hate to do it and find something after!

Clean looking build. 

The major issue I see with lowering the drive train is that you are placing everything below the frame.  A skid pan will protect it but you will still be snagging on items.

You really shouldn't be seeing any vibration on your front drive-line unless it is out of balance.  It is long enough that the angle shouldn't be to steep.  Is the vibration only there when you have the front hubs locked in?  What about with your hubs locked and the front drive-line removed? 

Also, with the CV style driveshaft you should have your front diff pointed directly at the T-Case instead of trying to have both the U-Joints on the same axis.  You may have to change the angles of your front spring mounts or add a shim to give your pinion angle.  Or it could just be your drive-line is out of balance.

Well the driveshaft is new from Low Range and is in phase. The pinion is pointed up towards the t case but not quite directly at it and there aren't any shims so I could try that but my concern is with the angle of the top joint at the t case. I still need to put a spacer in so I will need to make a new tranny crossmember to clear.

If I were to lower everything the only part that would hang below the frame is the tcase mount and it's heavily skidplated (Mighty Kong) and this thing has allot of clearance.

The case seems to be tilted back a bit as you can tell by the rear driveshaft.

Here's some pics. Do you think the shims would help?

Actually now that I look closer the transmission has been mounted 1/2" higher and the t case has been tilted back about 1 1/2". Maybe I'll just make a new tranny crossmember/ mount that'll lower the tranny and the front of the t case and that should do it.

Yes/No?

The T-Case has a bit of angle to it stock, it's thrown me off a few times.

Do you see the same vibrations with the front axles locked with the drive-line pulled?

Yeah but not as bad. If you get up to 30mph in 4hi it actually get quite violent!

Looking at that rear driveshaft, I would suspect that most of your vibrations are from it!



Rule #1 in driveline design is "Make the flanges Parallel!".

Tilting your rear dif up as indicated in the above picture causes the U-joints to operate out of phase with each other causing vibration and wear. 

See

http://www.4x4wire.com/toyota/tech/driveline/

and

http://www.4xshaft.com/driveline101.html

For a detailed explanation.

Exception to Rule #1:  If you use a Double-Cardan driveshaft, you may point the differential flange at the transfer case output if  you put the Double Cardan joint at the transfer case end.

See the above links for detailed info on Double Cardan setups.

I get the biggest laugh out of older, wildly-lifted pickup trucks that have regular driveshafts and the differentials pointed at the transfer case.  It's odd - I mostly see them at the Auto Parts store...

When I got the drive shaft I initially put the CV end at the t case but oddly enough it doesn't have enough movement for that angle which the single U joint does..

Also the Samurai pinions point at the t case in factory form which is also strange as I was always taught they should be parallel to avoid U joint wear. So if I want to turn the pinion down to make them parallel I would have to cut and spin the knuckle ball at the end of the housing to maintain proper caster. Then I'd have them parallel but both my joints would be at extreme angles.

Does that make any sense? 

The front drive-line on a stock vehicle is not at the proper angle.  But Suzuki also claims you should not be using 4wd on an SJ over 35mph. 

To get a little more angle out of your CV you might try cleaning/moding it.  The article claims you should get 35 degrees.  http://www.4x4wire.com/toyota/tech/cvmod/

As Ack said though, if your using the CV style Toy setup you need to have it on the T-Case end.  Looking at your angle I'm surprised it isn't already rubbing.

Good link thanks. I did turn it around yesterday and as I thought the cv binds so I was thinking about doing some sort of clearance mod. This link will help with that.

I also have 2 stock suspended sammies here so I got out my measuring tape. The bottom of the front flange on the tcase is in fact 1/4 " higher than the rear. So I measured the lifted one with the custom mount and it is almost 1 and 1/4" higher in front than in the rear.

So I figure I can make a new mount and bring the front of the tcase down just under an inch and clearance the cv like in the link and that should take care of the problem. This rig will not be driven on the highway in the winter so it only needs 4WD for trail duty. As long as it can do around 35-40mph.

I do appreciate the help guys!

why don't you get the liquid balancing bands. and give that a try.
http://forums.4wheeloffroad.com/70/6416631/new-products/sun-tech-innovations-driveshaft-balance-masters-ju/index.html

It look's to me like your front shaft is 90 degrees out of phase

Luke,

Looks to me as though you're right.

You know when you post a question and pictures and go through a big shpeel and some one points out the obvious and you feel like an idiot!

Well I do! lol

Thanks Luke I'm gonna go down to the shop with my tail between my legs and fix that!

I'm from BC it must be the weed.

I always forget those can be out of phase...

Nice catch Luke. 

I want those seats