Rb20 vs rb25 transmission?

[lilskyline240]

im going to be puttin a rb25 into my 73 240z this spring and i have a motor wiring harness and ecu but no transmission. I can find rb20 transmission's easier and ALOT cheaper.....my question is, how much weaker is it? like what HP level will it start to be a problem at?

[Joe]

its hard to give an exact number, but somewhere in the 4-500whp range is when they start to self destruct.

[nissanman04]

from what i've read, the 25 transmission is a lot beefier than the 20 transmission, hence the significant weight difference between the two engine swaps.

[lilskyline240]

i only plan on makin 400whp MAX and if i would go anything more than that i would definitely need the rb25 transmission.....so i will probably just go with a rb20 transmission because its like $800 cheaper....for that, i could buy a good clutch for the rb20 trans

the rb20 trans will bolt to the rb25 block correct?

[Joe]

yes it will

<- rb20 trans on rb25.

[lilskyline240]

thanks....this definitely will save me tons of money.....can i run an auto ecu even tho the car will be manual?

[Sil240]

Yeah I think the only diff between the Auto and the Manual ecu is the timing20 degrees and 15 degrees

[Joe]

if you ground one of the AT sensor wires on the ECU it will run it in "normal" timing. i forgot which one but i did it on mine. runs smoother

(it only effects base timing)

<- auto ECU on a manual hahaha

[OpeLok]

side by side comparison of 20v 25 transmission

[Chaos the Xile]

OpeLok I'm glad that you posted that pic up cause I was getting ready tooo. The internals of the 25 are VERY Strong. If you have ever seen a RB26 Drag car, RWD setup they have 25 trannies and push over 1200WHP