Anyone have directions on how to do a gear swap in the GDU? Ran an event at Gratten this weekend and didn't even have to use 6th. Ok, maybe a little but a shorter set of gears would have been really nice.
How tough a job is this?
@trackmnky, changing the gears is not difficult, but it is a little messy so it is easier to do at home then at the track.
Here is a quick summary of how to do it:
Step 1- Remove the lower line going from the GDU to the GDU Cooler to drain the gear fluid. Then reinstall the hose
Step 2 - Remove the fasteners from the perimeter of the left side GDU cover and remove the cover.
Step 3 - Put a rag between the two gears visible in the GDU. Then use a pneumatic or electric lug gun to remove the nuts holding on each gear. It is important that you make sure which way to turn the nuts (it is marked on the nuts). You will notice that the nuts are staked to keep them from coming loose so it takes a bit of force to remove them.
Step 4 - Replace the gears with the new set and install / torque the new nuts. It is recommended that new nuts are used because they are staked in place, but it is possible to reuse them in a pinch. Then stake the nuts in place.
Step 5 - Reinstall and torque the side cover. You will notice that the lock washers are unique so if you loose one don't try and use a standard lock washer.
Step 6 - Refill the fluid (make sure that you reinstalled the line to drain the fluid). It is important to only fill the fluid until it reaches the level plug on the side of the case. If you overfill the GDU it will spit gear oil out of the vent. Remember to re-safety wire the drain plug.
Charley
Thanks Charley. Doesn't sound bad at all. What sealant do you use to seal the cover?
Looks like I'll be ordering a set of gears soon. Just need to figure out which ones now. 🙂
There is an o-ring so no sealant is needed. Sometimes it helps to put a little grease in the o ring slot to help hold the o ring in place while you put on the cover. If you get a new o ring it will seem like it is 3/4" to long to fit in the slot but if you keep working it into place you can eventually get it to stay in the slot.
Regarding gearing, if you want some shorter gears you might want to try the 3.23's they give you better acceleration and only a minimal decrease in top speed. The one thing I noticed with the 3.23's is you go through the gears much quicker and it is easier to over rev. I know that Spring Mountain keeps most of the common gearing in stock.
Charley
Looking for the gear ratio's in the trans now so I can plug them into my gearing/speed calculation spreadsheet. I think they might be in the manual.
I'm probably going to go with your suggestion of 3.23's. Stradale recommended 3.2's for the shorter tracks too. Should be a noticeable improvement over the 2.9's that are in the car now.
Don't we have a rev limiter on the top end?
Thanks!
@trakmnky, there is a gear ratio speed vs RPM chart in the Radical Manual that Charley added to the resource library 👍
Thanks Crit, I'll take a look at that.
