Possible front end damage

[seagulljim]

Good evening, I own a fg649 with modified 2wd canter parabolic springs to suit my 4x4 crewcab and have removed the stock bumpstops and replaced them with ATW timberen? compressible bumpstops and lengthened stainless braided brakelines to cope with the added flex. The difference is significant and quite affordable and well worth doing.
These modifications have been in the veichle for about 2 years with no issues.
My concern is with approx 1 inch additional lift and the extra flex and give of the new front suspension set up is it possible for the front diff to contact the sump?
The front tailshaft now is noticeably more extended also and in a 4wd situation will the lack of spline in contact possibly cause some kind of failure?
Thoughts and possible fixes would be appreciated
Thank you

 

[SkiFreak]

What could be another potential issue is the increased angle between the front diff yoke and the prop shaft.
That can result in excessive noise and wear of the front uni joint.
In an ideal world, the yoke and prop shaft are inline. that will give you the optimal loggevitiy of the uni joint, The double cardan joint at the top is not really affected with a bit of an increase in angle, as that is what they are designed to deal with.

As a basic test to see how much movement there is in the spline, jack the front end up and measure how much of the slide joint is exposed. To see how much it moves, wrap a cable tie around the top of the spline, take the truck up to about 60 km/h and brake as hard as you can. The cable tie will be pushed down the spline and you will get an idea of the range of movement that you have.
You should then be able to decide if you need to get the prop shaft modified to deal with the movement or not.

If you have increased the lift, i don't think you will be driving the diff into the sump. The FG also has a cutout section in the sump to deal with having a diff up front.

 

[Howard70]

......My concern is with approx 1 inch additional lift and the extra flex and give of the new front suspension set up is it possible for the front diff to contact the sump?....

Hello seagulljim:

Short answer - Yes it may be possible, but hopefully unlikely. I know three FGs with modified front suspension that have experienced contact between the yoke and the sump. I can only speak of the details in my case as I only heard of the other two from the owners. We were over GVW by 500 lbs, hit a serious pothole at 20 mph on a paved logging road, our nitrogen assisted shocks had lost their charge (ignorant maintenance on my part), and the yoke left a very small scratch on the sump w/o damage.
We’ve had no further issues and never had any problems with off highway driving slow 4x4 flexing etc. We drive now more carefully, keep the shocks charged, and watch our weight.

Howard Snell

 

[gait]

when I first fitted parabolics I noticed a vibration from front drive shaft above about 30km/hr. Unable to use 4wd for anything beyond getting past obstacles. There was noticeable play in the splines. I had the drive shaft rebuilt (local Hardy Spicer workshop), and lengthened. Problem solved.

 

[Aussie Iron]

Removing or modifying (cutting them in half) the front bump stops can lead to the tailshaft hitting the sump when the axle articulates. They are your safety stop so that they never contact. Don't do it.
Raising the front end suspension will make the front tailshaft too short - this can be fixed by getting a 25mm spacer made to bolt in the tailshaft at the front diff pinion. Done lots of time when only a small difference is needed. Now raising the front suspension, if you look at the geometry of doing it the pinion is angled further down so fitting Caster wedges is recommended to bring the pinion (and front axle) back into correct angle.

Dan.

 

[seagulljim]

What could be another potential issue is the increased angle between the front diff yoke and the prop shaft.
That can result in excessive noise and wear of the front uni joint.
In an ideal world, the yoke and prop shaft are inline. that will give you the optimal loggevitiy of the uni joint, The double cardan joint at the top is not really affected with a bit of an increase in angle, as that is what they are designed to deal with.

As a basic test to see how much movement there is in the spline, jack the front end up and measure how much of the slide joint is exposed. To see how much it moves, wrap a cable tie around the top of the spline, take the truck up to about 60 km/h and brake as hard as you can. The cable tie will be pushed down the spline and you will get an idea of the range of movement that you have.
You should then be able to decide if you need to get the prop shaft modified to deal with the movement or not.

If you have increased the lift, i don't think you will be driving the diff into the sump. The FG also has a cutout section in the sump to deal with having a diff up front.

Thank you for your advice, I will get onto it....cheers

 

[seagulljim]

Hello seagulljim:

Short answer - Yes it may be possible, but hopefully unlikely. I know three FGs with modified front suspension that have experienced contact between the yoke and the sump. I can only speak of the details in my case as I only heard of the other two from the owners. We were over GVW by 500 lbs, hit a serious pothole at 20 mph on a paved logging road, our nitrogen assisted shocks had lost their charge (ignorant maintenance on my part), and the yoke left a very small scratch on the sump w/o damage.
We’ve had no further issues and never had any problems with off highway driving slow 4x4 flexing etc. We drive now more carefully, keep the shocks charged, and watch our weight.

Howard Snell

Thanks for that, I will make sure I drive to the conditions

 

[seagulljim]

when I first fitted parabolics I noticed a vibration from front drive shaft above about 30km/hr. Unable to use 4wd for anything beyond getting past obstacles. There was noticeable play in the splines. I had the drive shaft rebuilt (local Hardy Spicer workshop), and lengthened. Problem solved.

Roger, I'm not experiencing any vibrations ect ,thanks for your input

 

[seagulljim]

Removing or modifying (cutting them in half) the front bump stops can lead to the tailshaft hitting the sump when the axle articulates. They are your safety stop so that they never contact. Don't do it.
Raising the front end suspension will make the front tailshaft too short - this can be fixed by getting a 25mm spacer made to bolt in the tailshaft at the front diff pinion. Done lots of time when only a small difference is needed. Now raising the front suspension, if you look at the geometry of doing it the pinion is angled further down so fitting Caster wedges is recommended to bring the pinion (and front axle) back into correct angle.

Dan.

Thank you, I reckon I shall do as skifreak suggests to sort exactly how much meat I have to play with and more than likely use a tailshaft spacer, (I will get an old mate to knock one up),and certainly put some thought into the castor wedges as I need the veichle to be 100% reliable.
Thank you Dan,and every one else for your advice