Noisy Hewland DGB trans

I have a GT car that has a Hewland DGB transmission. I am new to Hewlands and dog boxes - my prior experience is with older Porsche transmissions. My DGB seems noisy to me when the car is idling in neutral. It sounds like rattling metal, and got my attention quickly the first time I started the car. The noise goes away when I disengage the clutch (neutral or in gear), and I do not hear the noise when I am driving the car at any speed. I do not hear grinding, banging, or other noises.

I asked a mechanic who worked on this car previously, and he said he thought it was normal based on what I was describing. I'm wanting to get additional opinions. Thoughts?

Scott

Normal to clatter at idle

It can be normal, but if it continues to make noise when driven under load, it could be an indication of a broken (or in the process of breaking tooth) in the gearbox. Consider putting the car on jackstands, and putting it into gear with a bit of drag on the brakes. It should be much quieter -- if not, then I would take it apart and examine the gears very closely to make sure you don't have a mismatched set, broken tooth, etc.

I recently had this exact problem on a Sadev gearbox and caught a tooth before it broke

https://www.apexspeed.com/forums/att...id=84672&stc=1

Lucky catch. Had a dog ring snap in two in a Staffs on the track once. I was lucky too. if it was my DGB, I would pull it apart and check everything. Very cheap compared to teeth breaking and really making a mess.

Thanks guys. I should have mentioned that I pulled the gearbox apart to inspect it before I started the car. I disassembled the gear stack and examined everything - it all looked fine to me. I was just surprised at the rattling/clattering noise when in neutral. Sounds like it should be fine.

Scott

Wasn't there a difference between DG and DGB dog rings? Look identical fit fine in either box but the dogs are longer on one version.

Yes. The DGB dog teeth are taller than the DG, but otherwise dimensionally the same. You could put a DG dog ring in a DGB and it would work, but the dog teeth wouldn't have as much engagement area with the gears. I was told by Hewland that they built the DGB because the DG300's were having trouble making it through the longer endurance races.

The gears are a little different too. DGB gears also have the extra height on the dog teeth. The gross dimensions of DG and DGB gears are almost the same, and you can put a DG gear into a DGB and it will *almost* fit, but there are some differences. The width of a DG300 non-fixed gear (the one that rides on the roller bearing) is like .010" more where it mates with the hub. The non-fixed gear will rub against the gear next to it, and the trans binds when you torque the nuts on the end of the shafts. Ask me how I know this :/. A guy sold me a bunch of "DGB" gearsets that turned out to be DG300 …

Let me know if anyone is looking for some DG300 gearsets ;)

Scott

If you need DG-B parts or need gears PM me, I got a lot.

Dog boxes typically are a bit noisey . But if it sounds like a box rocks banging around there is a good chance there is a bent tooth somewhere in the mix . Each gear needs to be inspected .