Petrol Head

When assembling my front diff as per the manufacturers instructions it feels really notchy when turning the outdrives by hand. I took out the shims that go behind the small gears inside the diff and it seems to be a lot smoother. The rear and centre diffs are smooth WITH the shims inside.

Do you think I will have a problem with the front diff with the shims removed?

Also, there is a lot of discussion about shimming the diff inside the plastic diff housing. My diffs hardly move without any shims added to the outdrives. The instructions say to add shims to reduce backlash but I don't know what backlash is?

I am tempted just to put the shims in anyway to be sure.

Any ideas?

vtrick

Petrol, I had this situation once and found it to be the small 3mm case plug screwed in too far. Yes you need to keep the washers on the shafts inside the diff as per the instructions.

Petrol Head

I just put the small shims back into the diff and it is virtually locked. I am going to have to take some out to loosen it up a bit. If the gasket was a bit thicker then that would have done the job for sure.

[sm=tired.gif][sm=tired.gif]

ringneck

i had that same issue with mine to when you assemble the diff it will be very tight and when you put it in the houseing just shim it so the ring and pinion are as loose as you can get it wich it will still be tight. when the truck is finished the 1st time you run it just run some figure 8 patterns fairly slow and that will break the diffs in and loosen them up to the point of needing re shimed. make sure you also clean out the diff fluid and replace it too cause you will have small metal fragments from break in and then you can shimm the back lash on the pinion and ring gear. even when the truck is almost done and you have tires on it you can roll it across the floor and that to will help loosen the diffs up. i to was alittle scepticle about runnin it with the diffs that tight but after a tank of fuel they were really loosend up and i just replaced all 3 diff fluids and re shimmed them all and its been a rocket ever since and have broken or bent nothing on this rig. hope this helped.

noximus

i suggest after you shim your diffs this time around, to re check them and shim them accordingly.

i had to re shim after the first 5 tanks, after that its been all good in the hood. i had to do the same with my LSP..so its nothing out of the ordinary for me here.

jimk2

Mine were the same, Mega tight when you turn the two drive cups. I'm assuming it will bed in and loosen up. But I also heard that putting in 2 diff gaskets sorted this out.

The back lash setting was straight forwar as there are 1 thick and 1 thin shim per diff.

wide_open247

I used two gaskets in and problem solved. Fitted perfect, but after you break it in take the second gasket out. And always be sure to watch your shimming

rcboxer

when you guys shim the diffs are you shimming the gears inside the diff or the outside by the output shafts for the axles? also how can you tell when you need to re-shim them, what should i look for? i was wondering because ( i haven't even broken in my truck yet) my rear diff feels a little loose, i mean i can move it side to side a tiny bit, is that ok will i blow up my rear diff? thanks, ryan

Haulin bass

Theres four little shims that go inside the diff case, and then there are shims that go on after the bearings on the outdrives(I run one thick two thin on the ring gear side, two thin on the other side) and you should shim the pinnion with 1 or two of the 8mm axel shims.

Petrol Head

Haulin, did you get all those shims in the ST-R kit?

Is it possible for the pinion to rub on the diff casing if it is shimmed too much or should the gearing prevent it from doing so?

Thanks.

Haulin bass

My pinnions before shimming were not even fully engaged with the ring gear the shims made it so the entire ring gear sat on the pinnion(there is still about 4-5mm before the pinnion touches the diff cup.
Yes All the shims I used came in the kit, but I used every single shim that comes with the truck.Just to be safe I would pick up a set of the outdrive shims and 8mm axel shims.

Petrol Head

Haulin, I am bit confused[&:].

Just shimmed mine and I have about 1mm (or less) between the end of the pinion and the diff cup (and my pinion sits perfectly on the ring gear).

If there was 4-5mm then the pinion would not touch the ring gear?

Haulin bass

Sorry it was early and I took a guess I can just fit a flatblade screwdriver inbetween my pinnion and diffcase through the bottom of the bulkhead when assembled.

jimk2

I have never shimmed my pinions and have built 3 kyosho MP777's.
I always set the back lash, then set the grub screw on the UJ so the pinion cannot move forward and hit the diff case. I do spend a little time trying to achieve a good fit and free running drive train.

I used 1 thick and 1 thin on the drive cups when shimming that's what was in my kit.

Petrol Head

I've had the diffs out three times now and am getting rather sick. I need to finish this kit so that I can get my engine in when it arrives from HK.

I have put on one thick and one thin shim on the ring gear side and one thin on the other. One shim on the pinion so that it sits neatly on the ring gear (but very close to the diff cup. Pushed the pinion back whilst tightening the grub screw on the UJ though).

That's the way its going to stay now until I have run it in. I'll open them up again after about three to four tanks.

Thanks guys for your advice