Front and rear diff rebuild...

[DrFizz2k1]

Ok.. So I was planning to race on Friday night... Had been to the track for practice and felt pretty good about racing... BUT... I had not changed anything on the truck setup wise from when i took it out of the box...

I decided to start with the Slayden setup and then tweak it from there for my track and driving style. I opened the rear diff and emptied the factory grease, and filled it with 5000wt. worked out air bubbles... re installed it with new bearings, lubed the ring and pinion... put it back together... success.. smooth as glass!

went to the front diff...

Emptied the 30k out of it, cleaned out the left over goo... cleaned all the gears.. built the housing side, filled it with 10000wt. worked out the air bubbles.. put the ring on... replaced the bearings, lubed the ring and pinion, put the diff in and awful binding... but only 1/2 way around the ring... hmmmm..

I could go on and on here.. but i'll try to keep this short... I checked everything... measured clearances with a micrometer, replaced the bearings again, rebuilt the diff again (3 times more total) used 2 sets of Jato seals, 1 set of revo seals... the diff action is smooth, I install the diff, and the ring and pinion bind still.. i went over and over this for 2 days.... HOURS..... Finally, i figure it out... 2 of the screws that secure the ring to the diff housing were too tight... it pulled the ring inward twards the center line and made it too snug on the pinion but only one one side... i figured a way to make it just tight, and not leak, and got rid of the binding.. im telling you.. i was down to counting threads on those screws.... put the diff in the truck and VOILA!!! Smooth diff action AND smooth ring and pinion...

So. After reading my great wall of text.. you ask why am I posting this....?

Well...

While I was rebuilding the diff with the correct rebuild kit I recalled many people ranting about binding within the diff.. and people saying to put it together minus some washer... a washer I never saw when i took the diff apart... I did find one of the blue seals in 3 pieces though, so i think there might have been a washer, but it got munched in there somehow...

anyway.. i was looking AGAIN at the exploded view of the diff from my Slash book, and i saw where it was saying to use the washer that was included in the Revo kit...

I ALWAYS follow the instructions... I am dyslexic... in fact to type this takes me hours!! no joke... (I use a spell checker in my browser so you all can read my posts.. LOL) So i read them over and over and over.. i looked at the pic a hundred times during this fiasco... but I was determined to use the washer, and I was convinced that the guys who were rebuilding without the washer were in fact doing it wrong...

THEY ARE!!!

If you follow the direction in the Slash book, you'll have binding, and you will be scratching your head wondering why and finally removing the washer....

But, if you follow the Revo instructions... well.. it works fantastic, and as intended..

THE SLASH VIEWS ARE WRONG!!!!

Here is the slash exploded view... note the washer being used between the rubber seal and the housing... it prevents proper seating of the seal AND gears and causes binding...





Now, here is the Revo one... Note the proper placement of the washer on the housing side, Placed on BEFORE the blue rubber seal...




I hope that clears things up for some folks.. I put it together the Revo way, and its is working perfect!

[osteologation]

i put it together the way i took it apart.

[eddiepfund]

If this works, I will be in love with you.

So what you are saying, is to take the diff apart, and swap the order of one the blue seals and washer on the diff.

So it would look like this? Housing - Rubber Seal - Washer?

[Randopolis]

I haven't gotten into this area as yet but I know it will be coming sooner or later. Thanks for taking the time to post your findings. Props.

[DrFizz2k1]

If this works, I will be in love with you.

So what you are saying, is to take the diff apart, and swap the order of one the blue seals and washer on the diff.

So it would look like this? Housing - Rubber Seal - Washer?

going along the shaft of the output (axle) yes, shaft with hole... housing... rubber seal, washer, beveled gear... that is the order.. refer to the Revo instructions i posted...

[DrFizz2k1]

i put it together the way i took it apart.

That would have possible, BUT.. there was NO washer and the blue seal was in three pieces...

[demons revo]

i have had binding in my diffs and even with this tip it still binds unless i take out the washer. any idea's????

thanks.

[cjohns58]

good grief! where are ya traxxas?

[peelin_out]

I had the same binding issue and this is with the "proper" build method, washer sandwiching the blue seal between the housing and itself.. this is on my pede 4x4... the exploded view for the pede shows the revo way btw.. tried several times and got binding each time so left the washer out.. I had a bit of seepage on that side but it seems to be dissipating now.

Anyways.. I had the same issue with binding between my ring and pinion gear and was going nuts trying to sort it out... I ended up using a different ring gear and a new diff housing on the pinion side and it finally went away.. I must have just gotten lucky with the right parts giving enough space there... but very interesting stuff on the ring gear screws. I will for sure remember that on my next rebuild. Thanks for the detailed experience on that!

edit: the issues I had with ring/pinion binding were on the front only also.. weird.

[RcPocketRocket]

good grief! where are ya traxxas?

Yes same thing here binding 1/4 the way around anyone have any answers before I tear it all the way apart.

[slash-4x4-jake]

*** im so confused lol ive never rebuilt a diff so ya

[Freelanceshots]

I don't know if this is the fix for your situation but my diffs would bind up if I tightened up the four hex bolts to tight. You just want them snug and then maybe half a turn past that. Tighten then in a cross pattern. put the first one in where it just starts to get tension and then skip to the opposite side and just barley tighten it. Skip across to the third one and put it in just like to other two. the forth one is last of course. Once all four are on the diff unit began to tighten them down one at a time until they just start to get tight. Go around and try to make them torqued all the same. Snug not super tight. When you tighten the bolts up to tight it binds the movement of the gears. there are o-rings that help the seal the unit up so things don't have to be super tight.

As you tighten the hex bolts up to secure the two halfs together turn the output shaft with your hand and make sure they spin properly. Movement gets to tight lossen a quarter turn or less.

Also make sure that o-rings 5381 and gears 5382 are full seated by pushing on the with your fingers before you close it up.

With the stuff that you took out it all needs to go back in. The new components installed in the diff may need a little time to adjust and break in so it might be a little tighter at first. Another note don't fill the diffs completely full of fluid. Leave some air. You definitely don't want to insert the final cover with the bevel gear inserted and then tighten down and compress the fluid.

Don't worry about the air bubbles. A full sized car's diff is not filled completely full. It has the ability to mix with air as the gears turn.

[sparksthewolf]

the binding is the gears themselves they aren't machined perfectly they are pressure pressed to make the main shape than tooled down to the shape and specs but not every vally in the gears are exact perfect mesh so it might be .002mm deep on one spot and .003 in another thats what causes the binding when you have a technical good mesh i personally took the diff put it together dry with a little graphite powder and little grease on the seals and stuck it in a drill and ran it for a day straight checking temp and seals mine wore themselves in took it apart cleaned it pit back in the lube and put them together worked a lot better and don't over tighten the screws holding the diff together i use a hard drive torque wrench to set all the screws at 5 inch lbs

[Banjoblue]

I'm finding that the side where the bearing slips onto the diff. cup is wearing out over and over? Replaced twice. Do they make an aluminum rear diff. for these?