General Gearbox Questions

[G0DZLR]

so after having replaced my blown 25DE box with a stronger 25DET box to cope with the obvious power gains of going from sub 100kws NA power to over 200kw forced, all is well apart from a couple of things.

firstly, when under mild load, 4th gear tends to crunch in, hence, you pretty much have to granny it into 4th otherwise youl hear a beautiful noise and feel it up your left arm. is this a sign of an aging box on its way out? clutch is bled properly too btw, every other gear theres no issue. is there anything i can do, without pulling it apart to prolong its life? additives or....im running castrol VMX80 in it atm. is there a thicker oil maybe i should be using

secondly, are 25DET speedo senders a different part to the 25DE ones...main reason is my speedo is pretty much half scaler, ie 20 is 40, 30 is 60, 40 is 80 etc...

help is much appreciated

[The Dan]

Ageing box my friend.

What's the bet you paid top dollar for it to?

This should serve as another lesson to everyone else out there that a series one, or even series two gearbox IS NOT WORTH WHAT PEOPLE ARE SELLING THEM FOR.

Sorry to hijack it abit there mate, just sick of hearing about people buying these things for $1500 and then having to fork out another $1300 to rebuild them. I hope you didn't pay more than that.

You can try a different oil but it's not about how thick it is, it's how well the synchro operates in that oil. I wouls actually suggest a thinner oil like transmission fluid as it will help the synchro grab the gear easier. But be warned, it's a last stand and the gearbox may develop small leaks in about 6 months. Use the time to save for a rebuild

[The Dan]

And yes the speedo drives are different

[G0DZLR]

hmm, anyone know what exactly i should use in this case then? someone did suggest to me a motul "shockproof" fluid? not sure what it is and where i get it but yeah. so far theres been no whines or bearing noises so i guess thats a good sign for now.

and thanks for the news daniel...

[The Dan]

The shockproof oil is made by redline and is very expensive. It CAN help sometimes but the last couple of cars I have put that stuff in, we have been having problems with it spitting it out when the box gets warm.

You could try the Motul Gear FF - part # 18-502-01 as it can help sometimes. I have put that into a few tired boxes and it works well.

If it doesn't, drain it out into a clean container so you can use it again after the rebuild.

Put in dextron 3 in the meantime. Should improve it out of sight failing the motul.

Alternatively, you might just have to shift slower