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How To Tell If My Gearbox Is A Dogbox Or An Aftermarket Box Without Taking It Out?

J-Boy
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jantolis Proficient

jantolis

Posted
Posted

If it's a dogbox it usually makes a whinning sound all the time. They are also alot harder to drive at first. After market gearboxes i'm not sure if they make the same sound.

Bass Junky Grand Master

Bass Junky

Posted
Posted

try this.

Put it in first.

Flatten right foot on floor.

Accelerate to 7500 rpm, change gear as quickly as possible without using the clutch.

If it goes into gear and makes a bang but keeps going, she's a dog box.

If it doesn't go in, or goes in then shits itself all over the road, it's not a dog box.

Then try it without the taking your foot off the throttle!

On a serious note, you' know from the V8Supercar whine that they give off. The faster you go, the higher the whine. Like the diff of a fu(ckarsed old taxi

saliya Rising Star

saliya

Posted
Posted

Hi,

There's a heap of info at the PPG or PAR websites.

In particular, have a read of the PAR FAQ

A dog-engagement box has no synchromesh/synchronizers on one or more gears.

Rather than gradually selecting a gear (and allowing the synchro to work)

you basically slam the gear in as fast as possible with a dog box. This needs to

be done while the box is unloaded. You definitely need to find out - driving a dogbox

like a synchro box apparently causes rapid dog wear.

You can't tell a dog-box by the whine - when the dogs are engaged (with or without

synchromesh) they are not moving relative to one another and should be making no noise.

The gearbox whine in racecars is created mainly by the gearset - most racecars

have straight-cut gears (because of strength and no-lateral-load reasons, amongst others),

and it is the teeth of the straight-cut gears meshing and unmeshing that makes the whine.

Helical gears (like those in an OEM gearbox) make much less noise; and you can

have helical gears with synchros or without (that is, you can have a helically-geared dogbox).

A dog-engagement box will feel just like a box without synchros : ) One of the ways you can

tell by noise is if it makes a noticeable 'clunk' when you select first gear from a standstill.

I'm sure there are others...

Regards,

Saliya

Bass Junky Grand Master

Bass Junky

Posted
Posted

J-Boy.

Yep, but that's half the fun.

saliya.

I was under the impression that you wouldn't have a dog engagement box on anything other than a straight cut gearset.

There's not much point in changing to og engagement with normal helical cut gears as there is no strength advantage.

Straight cut gears is much stronger because there is considerably more meat in the gears.

saliya Rising Star

saliya

Posted
Posted (edited)
J-Boy.

Yep, but that's half the fun.

saliya.

I was under the impression that you wouldn't have a dog engagement box on anything other than a straight cut gearset.

There's not much point in changing to og engagement with normal helical cut gears as there is no strength advantage.

Straight cut gears is much stronger because there is considerably more meat in the gears.

Hey,

according to some, it's actually helical gearsets that have a strength advantage on a strict size-for-size

basis - this kind of makes sense, because with a helical gearset there are more teeth engaged at any

one time (which translates to less push on any individual tooth). But yes, at very high loadings the

side loads become significant - so in theory, right at the top of the strength tree is a straight cut

box that has no lateral loads.

According to PAR, the 'strength' advantage of dog vs synchro is more to do with gear size rather

than engagement method; the dog-engagement arrangement takes up less room than synchro,

allowing more space for a wider gear. This extra width can then be used for either helical or

straight gears...

I'd guess that because they're harder to make, helical aftermarket gearsets have been around for

less time and probably cost more, so yes, you're "more likely" to see a straight-cut aftermarket

gearset than a helical set statistically. But straight-cut gears != dog-engagement, is the point I

was trying to make.

Dog engagement has the advantage of virtually requiring high-speed shifting - apply pressure to the

shifter, unload the box and wham, you're in the next gear. You can unload either electrically

(ignition 'blipper' or similar) or mechanically (lift throttle for long enough).

I'm certainly considering going down the path of a dog-engagement helical gearset sometime

in the not-too-distant future; I don't want the noise of straight-cut gears but I love the high-speed

shifts that are possible. It will depend primarily on how long my current box lasts, what the

service/rebuild intervals for the dogbox are, and whether I can live without synchros in real life :P

Regards,

Saliya

Edited by saliya
Beer Baron Grand Master

Beer Baron

Posted
Posted

the real question is why do you think it has anything other than a standard box? i would think if it had a dog box in it you would know about it as the first time you jumped in it would have been practically undriveable.

J-Boy Mentor

J-Boy

Posted
  • Author
Posted

Well i do get sorta like a clunk sound going into first...sometimes when shifting fast from 1st into 2nd i get a loud "bang" kindda sound and the gear engages, but i am using the clutch...every gear change feels like as if it goes in very hard somehow...like a very bare metal feeling...no cushioning on impact wotsoever....it does whine as well...somehow i dont really dare to slam it from 1st into 2nd without the clutch....

  • 2 weeks later...
9krpm Mentor

9krpm

Posted
Posted

let me take it for a spin next time and I will let you know if it's a dogbox or not. Like beer baron said if it's a dogbox you will know it aldready. It's not that simple to drive a dogbox but not very difficult once u learn what to do.

one quick test is while the car is idling, clutch in and put it into first gear. If it goes in smoothly and THEN bang ==> dog box

If it's difficult to go into gear or make noise as it goes in ==> stuffed synchro. This is bad new because if your first gear syncrho is stuffed then more than likely the others are not healthy either!

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