55 replies to this topic

[OCD]

***edit: Sorry, I think I accidentally responded to an old post on page-1. Doh!

According to the instructions, you must leave air inside. I imagine without any air, you would run into leakage problems as internal temperature fluctuates. Higher temp = higher pressure. Without enough air to allow compression , you will hydro-lock and blow out the seals. Just like an off-road damper w/ too little air inside.

BTW: Air inside should be perfectly fine. When the diff is spinning, all the bubbles will collect in the center away from the bevel gears as the dense fluid is spun to the outside via centripetal acceleration (mistakenly referred to as centrifugal force).

I was thinking of cavitation being the main culprit here; If you completely break grip and one wheel is stationary while the other is in full-slip, you're gonna have a lot of spin inside that housing. 1:1 diffs have vanes and pockets to assume the extra volume, but Tamiya seems to have solved this issue by just having you partially fill the housing. Occam's Razor I guess?

[JeepnMike]

Exactly how much fluid to put in the diff may take some tinkering. For the first test with the gear diffs (F&R), I likely over-filled the diffs and the seals did blow out (after many runs) and there wasn't any oil left in the diffs when I rebuilt them last weekend. So lesson #1, don't try to fill them all the way up. For this last rebuild, I tried to fill them what I thought was full enough with a little bit of room for air, AND added a somewhat healthy amount of Green Slime (thanks Paul!) to the seals. I ran my buggy on a pretty gnarly track through 4 5000mah LiPo packs over the weekend and I think they still may have leaked a little but not nearly as bad as before. Of course I want as much LSD effect as I can get so your instinct is to put as much fluid as you can, you just have to try to refrain or you will be rebuilding your diffs as much with the gears as you would with the ball diffs.

I will say with 10K fluid in the front and 3K in the back, it handles extremely well and is very predictable in corners on loose dirt and pulls just fine. I ran plently of power and battery in my car and didn't see any hints of wear on any parts of the diff in my last rebuild so they are still getting a big thumbs up from me.

[speedy_w_beans]

I wouldn't fill the diff higher than the cross pins for the spider gears. A little bit of air is fine and even necessary. Glad you like the 10k/3k combination! If you like that combination and think you'll stick with it long-term, you can always replace the green slime with black silicone RTV, like what is available from Permatex.

-Paul

[Raman36]

I've been watching these pop up on eBay recently; Does anyone know if these fit either the TA04 or TRF415 cars?

I really like the idea of making one of them a center diff in a TLT.

TA04 actually had a gear diff option. It came standard on the TA04S. The gear case looks like its discontinued, ( prob find it in a google search ), the bevel gears however are still available

http://www.tamiyausa.com/product/item.php?product-id=50891

http://www.tamiyausa.com/product/item.php?product-id=50602

The bevel gears we're made out of metal. Prob aluminium.

[OCD]

TA04 actually had a gear diff option. It came standard on the TA04S. The gear case looks like its discontinued, ( prob find it in a google search ), the bevel gears however are still available

http://www.tamiyausa...roduct-id=50891

http://www.tamiyausa...roduct-id=50602

The bevel gears we're made out of metal. Prob aluminium.

Yup, and I already have one in my TLT as well. It's just a plain old gear diff though; Doesn't hold oil so I don't have the ability to tune it like the viscous diff.

[Yello]

I still have the "hybrid" power train in my DB01, that is, the gear diff in the back with stock 1k oil and the ball diff in the front.

What I discovered after many many many runs is that only a tiny amount of oil leaked- perhaps residual oil squeezed out when the halves were screwed together- when the diff was placed in. And that's judging only by the amount of dust and dirt stuck to the outshafts. Otherwise, the diff has held up fine.

Another thing I discovered is that you have to be careful about the way you install these gear diffs as they can bind as you tighten down the gear covers. I'd recommend removing the two washers for at least one of the ball bearings on the outshafts as they don't seem to be neccesary (unlike on the ball diffs). Doing so should ensure that the diff does't bind anywhere against the cover.

The gear diff, IMO, is probably the single best hopup one can buy for the DB01. Definitely recommended. Only the pros should stick with the ball diffs.