Driveline Angles Series

[allende]

Am busy upgrading springs to 109's with military shackles on my 88. Anybody have the data on driveline angles that have to be maintained so the ujoints don't break? British Pacific says a 6 deg shim needed at the front, but nothing about the rear. Ideas?

[TeriAnn]

Am busy upgrading springs to 109's with military shackles on my 88. Anybody have the data on driveline angles that have to be maintained so the ujoints don't break? British Pacific says a 6 deg shim needed at the front, but nothing about the rear. Ideas?

When you add extended front shackles to a civilian frame, the nose of the front diff points more to the ground, adding to the front prop shaft angle and it throws the steering king pin angle off.

The 6 degree shim corrects the steering geometry. The Testing was originally done on my "The Green Rover" at a front end alignment shop. The Green Rover was laser aligned with stock shackles (the king pin angle was spot on) then checked again with extended shackles and different shims. A 6 degree shim bought the king pin angle back to the pre shackle change king pin alignment. So if your Land Rover's king pin angle was within factory spec before the shackle change, a 6 degree wedge should return it to factory spec.

However, since you are increasing the vertical distance between the plain of the transfer case front output shaft and the plain or the diff pinion gear shaft, the angle on the front U joints will be greater. Front axles do not articulate much. Unless you play around with springs & shock mounts you can usually get away with a stock front prop shaft. Check your U joint mounting flanges for shiny spots after a short off road run. If you have them you will need to either go to a new custom prop shaft or have new ends put on your existing shaft.

Also look for a shiny metal ring where the front prop shaft crosses over the front of the bulkhead cross member. If you have contact you will need to make a divot where the prop shaft crosses over the front of the cross member. When the factory used extended shackles the factory also had a cross member divot to keep the prop shaft from contacting the cross member. It is a good idea to have one. Solid contact changes the angle of the pinion shaft enough to destroy R&P gears.

Now getting to the rear:

BP doesn't say anything about the rears because it was a non issue for my 109. The fronts were important primarily because of changes to to the steering geometry.

With the rear, the nose of the diff goes upwards, decreasing the angle on the rear U joints. However, it does change the rear pinion shaft plain so that it is less parallel to the transfer case output shaft plain, and the vertical distance between the flanges increase. This is not a real issue with 109's because of their long rear prop shafts but you may find vibration issues developing with that very short 88 rear prop shaft. The longer rear springs articulate more than the fronts do as well. I just don't feel comfortable about the stock 88 rear prop shaft. Especially since the LR factory did not use long shackles on an 88.

If it were me, I would contact Bill at Great Basin Land Rovers & have him make up a custom high angle prop shaft. I don't think you need a shim to bring the rear U joints back into their proper angle relationships but I've never dwelt with 88s. Bill will probably know.

I have high a Great Basin high angle U joint front prop shaft on my 109 & I'm quite happy with it.:thumb-up:

[allende]

Really great info and a great website. I'll call Bill

Allen on Vashon Island, WA

[yorker]

I've used the long shackles since '97 with no issues. The springs were new standard 88" springs though. long shackles were used on factory 88s- the Australian 2a 88s had them. BUT they also had lower front spring mounts as well like the 109 1 tons and military 109's.

[KevinNY]

My 88 coiler runs a rear shaft at about the max you can get away with. Tom Woods can make a shaft up for you cheap and it uses the more common and larger 1310 size u-joint. Thats what I'm running now and just accept yearly u-joint changes since they wear faster at high angles.

[yorker]

Kevin-

I know it is difficult since you have a designa chassis but do you know how much lift you have as compared to a standard leafer? You are running OME springs still?

[Mercedesrover]

I run 3-leaf paras and military shackles in my 88" and also have Toyota centers that are hypoid which means the pinion is lower in the housing. Change the rear U-joints every year or so and you'll be fine.

jim

[J!m]

I also have military shackles on my 88. I run 109 station wagon front springs and 109 1-ton rear springs to carry the excessive weight of expeditions.

I used a set of shims in the front to correct my pinion angle: 1/2 inch thick at the rear, tapering to zero at the front with an alignment hole. (you will need longer u-bolts as well) This is pretty damn close to 6 degrees, but I did not check it that way, I used the "yard stick method" as explained below. I did not run any shim in the rear, but I did retain a set of (longer) limit straps which everyone likes to delete. Don't delete these, as they keep your brake line and drive shaft in one piece! I then drove this truck across North Africa for two months. It still runs and drives perfectly today.

The short version of the story is that the exit of the transfer case and the entrance to the diff should be parallel with the weight of the vehicle on it. (use a pair of yard sticks and a tape measure to check this) Angled up, toward the transfer case, is just as bad as angling away from it (unless you have a double u-joint set-up at the transfer box as some have added with big crazy lifts).

Now, to throw a wrench in the works, my 110 has the front diff angled up, toward the transfer box. This normally makes minced meat of a u-joint in about a week. The way LR got around this is to off set the u-joints 45 degrees, rather than 90 degrees as is normal for the majority of vehicles. I don't understand it, because angling the u-joints off of 90 also makes minced meat of u-joints. This is why it is so critical to keep the splines aligned when disassembling a drive shaft... I had some bad bushings in the rear of the 110, allowing about 2 degrees of play, and I destroyed the rear u-joint this way. So, it's important.