DOG box driving on the street

Hi folks,

i'm driving a 2007 Seat Leon Cupra. The engine and drivetrain are swapped, with those from a Golf MK5 R32.

The stock gearbox is to weak for the power we're aiming for. So i have the option to reinforce gear 3,4,5,6 for dog engaged gears. But the car isnt used at the track only, it's a road legal car and will be driven (mostly) on the streets.

What are your experiences, driving a (partial) dog box on the street?

The life expectancy of a dog box has everything to do with the driver. There is no reason you couldn't street drive with a dog box, however it does need to be treated correctly. Slow shifting will damage the dogs quickly, so the key is to make all of your shifts fast and positive - in fact the faster and more aggressive, the better.

Many people confuse dog engagement with the term 'straight cut' and assume that a dog box will be noisy on the road. While it's true that the majority of dog boxes also use straight cut gears, they equally can be manufactured with helical cut gears (like we would see in a factory box). Helical cut gears are quiet while a straight cut gear whines and this would become frustrating for a road car. It all depends on how your gear set is manufactured and what you are prepared to put up with.

Helical cut, so no whine :)

But my real issue is, can they be driven using the clutch? Up & downshifts? I'm not looking for super hard shifts, that will cause the gearbox housing to crack (seen a couple of those). So i can 'dampen' the engagement a bit with the clutch.

I can't remember where but I seen this video linked up the other day, I think it was on the HP Academy Facebook post on dog boxes

https://m.youtube.com/watch?v=n_1jO64tuQA

Having never driven a dogbox I thought it explained everything really well

You can shift a dog box with or without the clutch. For around town running, it is definitely smoother to use the clutch as clutchless shifting will cause a shock load through the drivetrain as the shafts in the gearbox are speed matched by the dogs engaging. Under race conditions this isn't a big deal but it can be uncomfortable around town or at low speeds.

I wouldn't want to start a new thread.

What oil do you guys using for Dogboxes and sequential gear boxes?

Most gear oil are 75W-90 API GL-4. But I think a thinker oil like the Castrol Syntrans Limited slip 75W-140 API GL-5 will be better sweeted. What I can remeber the API-GL5 has a better lubrication to gears, since the API-GL4 oils has some kind of friction modifier in it for the synchro rings. That isn't neede in a Dog box, so a lubricant with best possible lubrication should be better, isn't it?

My diff manufacturer says:

Performance Gear Oils we recommend:

Requirement Oil

75W90 Motul Gear 300 (100118 1l)

75W140 Motul Gear Competition (101161 1l)

Quite funny you replied to this thread, since the actual build of my gearbox just started.

I would recommend talking to the gearbox manufacturer first and see if they have a recommendation. Often they will be a little fussy about the type of oil being used so it pays to take their advice first and foremost.

I've done some research and found out that most manufacturer recommend some thick oil (mostyl 75W-140) for their dox box or sequential gearboxes.

Actually Dreth recomends the Castrol Syntrax LSD 75W-140 i mentioned for theire gearboxes. I filled that oil into the KAPS dogbox. All went fine and smooth at the first race. We will see how the gearbox will look like at the next revision, but I feel confident that I will work fine.

Besides the Motul competion 75W-140 are recommended from many manufacturers and motul sais that's especially made for competiton gearboxes and use. Should be a very good oil I think. I has also a nice blue colour ;-)

I've done some research and found out that most manufacturer recommends some thick oil (mostyl 75W-140) for their dox box or sequential gearboxes.

Actually Dreth recommends the Castrol Syntrax LSD 75W-140 i mentioned for their gearboxes. I filled that oil into the KAPS dogbox. All went fine and smooth at the first race. We will see how the gearbox will look like at the next revision, but I feel confident that it will work fine.

Besides the Motul competion 75W-140 are recommended from many manufacturers and Motul says that's especially made for competiton gearboxes and use. Should be a very good oil I think. It has also a nice blue colour ;-)