Suspension Underslinging....

Ben Kelly

New Member
Apr 23, 2016
3
0
1
47
Riddells Creek, Victoria
I know it may have been discussed before but what are people's thoughts on underslinging an axle? I have a 2007 Jayco Expanda single axle and towing it with a 2009 120 series Prado. I have just replaced springs and shocks on the Prado accordingly to the weight I'm carrying. I've also invested in a Hayman and Reece WDS, my problem is that my van sits too low and almost drags in the rear hence, needing to be raised. I have the tow hitch on the lowest it can go. I've been told underslinging will create more sway when towing. What other options do I have in raising the van?
Cheers.
 

Drover

Well-Known Member
Nov 7, 2013
12,723
19,450
113
QLD
I did a write up on the How To for underslinging your axle, just not sure where it is so you may have to search..............the bit about causing swaying and such is really BS if it's done properly, you will gain about 100mm, sometimes a bit less so measuring things up before hand is needed...............for starters with your van level measure between ground and the bottom of your hitch then with your tug measure from ground to bottom of ball, take away about 25mm, this will show where your tug hitch would roughly be sitting when loaded up with van, add 100mm to the vans measurement it should be very close to the tug measure.
If its more than 25mm you may have to change the profile on your tyres to lower or raise, mind depending on load/springs you may only get 80mm from rolling the axle but it is doable and I reckon a worthwhile mod......I will see if I can find a link....there is a certain way it must be done and does require some measuring etc, you cannot just rotate the axle, the brakes have to stay in the same position, the spacers need to be repositioned with care to keep the alighnment, it is an easy job ......just need jack stands, new U bolts, fish plates and spacers, tape measure and patience.
 
Last edited:

1DayIll

Well-Known Member
Apr 26, 2016
997
900
93
59
South Morang, Victoria
I did a write up on the How To for underslinging your axle, just not sure where it is so you may have to search..............the bit about causing swaying and such is really BS if it's done properly, you will gain about 100mm, sometimes a bit less so measuring things up before hand is needed...............for starters with your van level measure between ground and the bottom of your hitch then with your tug measure from ground to bottom of ball, take away about 25mm, this will show where your tug hitch would roughly be sitting when loaded up with van, add 100mm to the vans measurement it should be very close to the tug measure.
If its more than 25mm you may have to change the profile on your tyres to lower or raise, mind depending on load/springs you may only get 80mm from rolling the axle but it is doable and I reckon a worthwhile mod......I will see if I can find a link....there is a certain way it must be down and does require some measuring etc, you cannot just rotate the axle, the brakes have to stay in the same position, the spacers need to be repositioned with care to keep the alighnment, it is an easy job ......just need jack stands, new U bolts, fish plates and spacers, tape measure and patience.

And you make it sound so easy!
 

Drover

Well-Known Member
Nov 7, 2013
12,723
19,450
113
QLD
Just have to do it in a certain sequence, by the numbers as they say, no shortcuts mind as it can be dangerous......I did neglect to mention it should only be attempted if on level solid ground preferably concrete, as the van does need to be elevated, especially tour models to get the height needed to move things around, 2 ton jack stands, a couple of bottle jacks and a lot of common sense or you can be injured or worse.
 
  • Like
Reactions: bigcol

Jazdiver

Member
May 26, 2016
65
92
18
Berwick
Had mine done by a trailer professional, then had shocks fitted at the same time. Had the same issue as my Colorado is lifted and the van height was pulling the rear down. Came up about 100mm. Towed better. Images are on another thread somewhere if you search.
 
  • Like
Reactions: Drover and bigcol

jeff

Well-Known Member
Mar 4, 2013
413
414
63
200km south of Perth
We have recently finished under slinging our son's Hawk, we accomplished this in a day. You need someone to remove the positioning lugs on the axle and re-weld. It lifted the Hawk 110mm. It's been on a trip since and towed better.
We used stands at the rear and left van attached to car during the conversion.
Neither of us work in the motor industry, so accomplished this without any specific mechanical skills
 
  • Like
Reactions: Drover and bigcol

mikerezny

Well-Known Member
Sep 11, 2016
1,630
2,728
113
Mount Waverley, VIC
I just left the old spacers on mine and fitted new ones, for that just in case scenerio.........
Hi @Drover,
damn, damn, damn!!!!!

I have been following this article thinking should I, shouldn't I undersling the axle on the Penguin. Then the bit about welding put a spanner in the works so I decided I wouldn't.

THEN, I remembered that the Penguin was subjected to a recall before we picked it up and had to have the entire axle assembly changed. If I had been quick off the mark, I could have got them to undersling the new axle and it would have been done for free!
Actually it would have made it easier for them since they wouldn't have had to take one of the backing plates off to feed the new axle between the body and springs.

grumble, grumble grumble

Mike
 
  • Like
Reactions: bigcol

Drover

Well-Known Member
Nov 7, 2013
12,723
19,450
113
QLD
The spacers only need a spot weld, just to hold in place so it doesn't move untill you tighten up the U bolts, liquid steel would do the same job really.............................next holiday up to Gods Country we could knock it over in an afternoon.
 
  • Like
Reactions: mikerezny

Drover

Well-Known Member
Nov 7, 2013
12,723
19,450
113
QLD
Ha I missed that bit, yep remove wheel, pull a pin out and drop the spring, walk axle out and back under, replace spring.....
 
  • Like
Reactions: bigcol

Boots in Action

Well-Known Member
Mar 13, 2017
2,054
1,806
113
Ferny Grove, Queensland
Hi @Drover,
damn, damn, damn!!!!!

I have been following this article thinking should I, shouldn't I undersling the axle on the Penguin. Then the bit about welding put a spanner in the works so I decided I wouldn't.

THEN, I remembered that the Penguin was subjected to a recall before we picked it up and had to have the entire axle assembly changed. If I had been quick off the mark, I could have got them to undersling the new axle and it would have been done for free!
Actually it would have made it easier for them since they wouldn't have had to take one of the backing plates off to feed the new axle between the body and springs.

grumble, grumble grumble

Mike

Hi @mikerezny , I had the axle on my Penguin under slung without any problems. Could not do it myself even though single axle, not like the big boys on this forum. Cost was about $350.00 and well worth it where I go. Much greater clearance for front and rear body of Penguin, although axle is still the low point. Okay if not straddling humps etc. Now need a portable step to get in/out of van as height is approx 100mm higher. Remember, my tug is a 4WD Colorado and has a good clearance already, more than your current sedan tug I think. See some of my photos with the solar panels to get some idea of how it looks.
 

Boots in Action

Well-Known Member
Mar 13, 2017
2,054
1,806
113
Ferny Grove, Queensland
Ha I missed that bit, yep remove wheel, pull a pin out and drop the spring, walk axle out and back under, replace spring.....

Hi @ drover, who said you could not use a spanner!!! You have the wood on me in that particular field. You have been rather quiet lately. Are you still travelling to the North towards Cape York and beyond?? Safe travelling. Regards
 
  • Like
Reactions: bigcol

mikerezny

Well-Known Member
Sep 11, 2016
1,630
2,728
113
Mount Waverley, VIC

Boots in Action

Well-Known Member
Mar 13, 2017
2,054
1,806
113
Ferny Grove, Queensland
Hi @Boots in Action,
last I read was that @Drover was heading to Canberra to try out his new diesel heater in -4C. Then it stopped working and he wasn't happy.

http://expandasdownunder.com/threads/winter.10485/#post-179411

He hasn't managed to drum any sense into the Pollies that abound around there or teach them to shut up when they don't have anything worthwhile to say.

cheers
Mike
Hi @mikerezny , thanks for the info on @Drover . No wonder he has been quiet !! I guess he would not be very happy at all in the cold, and as for the pollies , I think he is pushing s... up hill in that regard. Opps - should not discuss that on this forum. Wandering off thread as @Drover would say!!
 

Drover

Well-Known Member
Nov 7, 2013
12,723
19,450
113
QLD
Don't mention the heater, as they say....lol,lol only 300kms from my work bench...............ignore Pollies, useless waste of oxygen................not much to comment on lately, just the same old questions returning..........