Jump to content
SAU Community

Recommended Posts

hey,

i have an RB25DET in the car and the 5spd blew last night.....drove it home and sound really bad...i think there will be teeth everywehre when i take it out, its a daily and i dont thrash it so can if i make anything else fit for a bit cheaper....eg...rb20 box or 32gtr gears inside my case etc....

cheeers

Link to comment
https://www.sau.com.au/forums/topic/220552-what-box-will-fit-my-rb25det/
Share on other sites

Any model of nissan that came with a rb motor in it, just make sure you get the correct cross member to go with it.

ie laurel, vl commodore, cefiro, skyline, 88 to 98

i think the question should be what gear box will fit your car model. as any rb box will bolt to any rb motor, etc

your best bet if you've blown your box is go to the wreckers and pick up an auto box for the time being, you will get one really cheap....even if its a 50$ job from a VL commodore for the time being...then save up hard and get new, stronger gears, and box rebuild

straight cut gears these should set you back a 1000 dollars or so but you will never break it again and also the box will then be a selling point of the car.

i would say dog engagment but these are really expensive...

two reasons for the straight cut teeth is

the two cogs have a more contact surface area, and arent herlical, they will be noisey but this will be normal....that is the whole reason car manufacturers make the gears herlical as it reduces the noise from the drive train and makes for a smooth transition between gear changes......

also because the cogs have straight cut teeth the cogs can be narrower but stronger than standard, the upside to this is the sinchro's can be thicker/stronger. snchro ring gears are seperate from the cog itself giving the gearshift the smooth interchange you feel, letting the gear you are selecting catch up to the speed of the engine matching the teeth to engage correctly.

dog engagement is where two pins engage each gear and only spin about 240 degrees then lock that is why you can shift without using the clutch once you are moving because the "dog's" lock onto the gear as you select it once locked the teeth on the cogs are matched, then all you have to do is dump the clutch or let it do its thing while rolling.

ask any race car driver, this is why the gear stick almost gets ripped out of your hand if your not onto it.

this is where the term DOGBOX comes from,

the down side to this is driveability, it's like driving a normal car with a twin plate clutch....you'll get used to it,

knocking it out of gear while the box is under load at the traffic lights for example is a no no because you will crunch it to get it back in first, make sure the car is stopped with the clutch in full then move it

also the advantage to this is having straight cut teeth the shafts wont have as much sideways force and therefore less stress on the bearings and case of the box.

Edited by nizmonut

awesome, are they the same length though? will my tail shaft fit all these gearboxes...is the lifspan of a dogbox going to be shorter. helical gears are lubricated slightly better due to the was they engage the oil can be pushed through instead of pushed out the sides?

also do you think if i bring the diff ratio down there wont be as much strain on the gearebox...hence an rb20 one might last a little while.

First off; What car and what box? Based on your nic would i be right assuming its a 180 with engine conversion?

Confirm you don't have a 20 box in there first before shelling out for internals for a 25 box.

Conversions done by someone else make it hard....

If the car was originally manual i reckon it's almost certainly the original VL box. If it was non turbo then the box would be very similar to an rb20 box and about the same strength.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Good morning all, Bit of a random question but figured I’d finally throw it out after wondering for a long while. Before I start, I'm hoping to do this purely out of personal preference. I think it would look better at night, and don't mind at all spending a few hours and dollars to get it done. I've copied this from a non-Skyline specific forum, so I apologize for the explanation of our headlight switch setup that we all know. Here we go: Zero lights (switch off) Parking lights (switch position 1) being a rectangular marker on the outside of the housing, my low beam being the projector in the centre (position 2), and a high beam triggered by my turn signal stalk. Most North American cars I’ve owned of this era have power to the amber corner (turning indicator) light as part of the first switch (parking lights). I’d love to have these amber corners receive power when the headlights and parking lights are on (headlight switch), yet still blink when using the turn signal which is of course a separate switch. Hopefully I’ve explained my question correctly. Is anyone aware of a way in which I might be able to achieve this? Thanks in advance
    • My heads are cathedral port! It's likely possible, but I don't want to add any extra moving parts (I know they don't move) between the heads, manifolds, etc. It will also affect how injectors/fuel rails etc sit and I don't really know if it would change how the FAST manifold goes/sits/fits. I have the LS6 steam pipes already as I have a very late LS1 block so it should be fine. I couldn't find anyone who had ever actually used one for this purpose, it seems 100% of people grind the water pump. The thermal spacers are 12mm and are half way to the cost of the newer water pump anyhow... so if it comes to that I suppose I'd rather buy a new pump. The bearing in the pump I do have is a little.. clunky, but it hasn't done that much time and I never noticed it when the car was together in the past few years, so..
    • The bushing has failed, not all that uncommon for a car of this age.  Any mechanic should be able to push in a new bushing for you, or you can probably buy the entire lower control arm, complete with bushes.
    • Could you not use "thermal" spacers to give the clearance, like the ones I used between the blower and head? That raised the manifold height by around 10-15mm Albeit the ones I used were for cathedral ports, but I assume they have similar for rectangular ports????
    • Thanks Paul I reached out to Autotainment but they no longer work on JDM cars as the guy who used to do the work moved on and is no longer doing that kind of work. I am talking with Level Up Audio though.
×
×
  • Create New...