diff swap in a 720 ute

[andyathome]

 

 

hi all, I need some advice.

Ive scored a drum to drum diff with a 3.8 ratio , so Im going to swap out my 4.8 to get butter revs on the motor way.

problem is Ive never done a leaf spring diff swap before.

The question is" are the leaf springs under tension when the truck is jacked up in the air".

I want to unbolt the spring hangers at the back of the truck and slide complete diff out , check bushes for the hangers at the same time and reassemble the same way.

my son will be helping and I dont want any supprises when we are under the truck.

Also when we are at it is there anything else we should be checking for while we have it appart.

 

cheers

[wayno]

If the wheels are off the ground, then the weight of the rearend is going to make things difficult to remove unless you support the rearend when removing the rear shackles, then you are good to go.

Fact is if you have two H190 rearends, why don't you just swap out the gearsets instead, it's a lot easier, and will take only a couple hours.

Check your driveline U-joints while it is out, and I am assuming that you checked the brakes on the new rearend before you started.

[andyathome]

that was my inital thought , only issue would be a drifference in the axial splines, will pull head of both and compare , if the same then thats what I will be doing, looking for the easy way :thumbup: 

have had the drive shaft extended and ballanced when I put the 5 speed in and checked U joints and now I have a vibration at speed.

When i grab the drive shaft with it in gear I have movement of about an 16th of a turn, Is that normal, maybe the cause of vibration.

[Charlie69]

What engine is in your truck?

 

Do you haul heavy loads?

 

What is the 3.8 rearend out of?

[andyathome]

Ive got a poxy z20 single spark plug with a 5 speed, a couple of dirt bikes would be the max load and the diff is out of a 85 720 ute like mine, Im guessing it might  be a desile version

[Charlie69]

3.8 should be fine then.

 

The splines are the same.  As far as I know all truck axle spline are the same on the H190 s from The 1965 520s up until Nissan stopped using the H190s in the hardbodies.  The car H190s used a different spline

 

I would do as Wayno suggested and swap the third members, just replace the gaskets.  opportune time to replace axle beings & seals if money is available.  Keep the axle shims on the axle they came off of.

 

1980 720 is the shortest width rear differential 1985-1986 being the widest.

[andyathome]

thanks for the advice , as soon as the diff shows up( the guy is delivering it to my door diff included $100 )  sweet deal.

I will pull the head and check ratio, and comapre mine,  replace axle beings & seals and definatley replace the gasket.

cant wait, see if I can get a better top end speed , then look into the vibration problem.