Nissan Gearbox strength - from L series to 34 GTR

[180bfj20det]

I have searched and cant find anything ellaborative enough.

Please does someone know of a website that outlines the strength of nissan boxes, sizes and other impt specs and pros and cons of each box?

If you know, post your knowledge and maybe I can collate the info amd make a site.

Cheers

[discopotato03]

180 JT , there is an American site called Handy Dandy Denny with ya or some such , do a search . Its mainly Z stuff but lots on transmissions .

Basically the Nissan / Datsun gearboxes use a series number based on the number of mm between the main and layshaft centers . The series and options of the boxes is usually cast in the side of the case . The numbers and letters define the bellhousing type and bolt pattern , the shift mechanism , the shaft centers and possibly the syncro type . There are lots of variations that were model specific but the basics are as follows for the 71 series 6 cyl boxes .

240K - 71mm centers , servo (Porsche) syncros 1-4 , warner syncro 5th

narrow gears , steel forks , steel front bearing cover / spigot , wide ratio .

260Z - same as above with closer ratios ie 2.9 1st , aluminium front bearing cover .

910 - FS5W71B - same but unique ratios ie 3.32 , 2.07 , 1.31 , 1 , 0.83 , alloy

forks , all Warner syncros .

Z18T - LZ5W71B - as above but wide ratio ie 3.6 1st , Z/L bellhousing .

FJET - as above with Skyline ratios ie 3.32 , 1.906 , 1.31 , 1 , 0.83 . Wider

gears , larger diameter syncro hub 1-2 , larger diameter 1-2 shift rod , FJ

bellhousing .

RB20T - RB71C as above with larger 3-4 syncro hub , C type shift mechanism , all

large shift rods , larger front lay gear bearing (also used in Ser 3 bird) .

Sub gear on front of laygear to prevent backlash at idle in neutral .

As for the larger boxes used with VG30's , RB25T's , RB26's and

RB30ET's I'm not sure of the specific numbers . I believe the shift

mechanism is partly external on Z32's . I think the ratios are wider on the

VLT box than R33 25T and the VL box may not have the twin cone

syncro hubs .

[jnr32r]

Is it certain that the RB25DET is internally stronger than the RB20DET?

I know it is externally bigger, but can anyone confirm that internally the 25 is stronger than the 20.

Ive had bearing probs with mine, but so has my friend in his R33 with less power and less Km's.

So still tossing up wether its worth swaping for a RB25 box....

[SteveL]

Is it certain that the RB25DET is internally stronger than the RB20DET?

I know it is externally bigger, but can anyone confirm that internally the 25 is stronger than the 20.

There is no question that an RB25DET gearbox is much stronger than an RB20DET gearbox. Everything - gears/shafts/bearings - is physically much bigger in the RB25DET gearbox.

[SteveL]

The series and options of the boxes is usually cast in the side of the case . The numbers and letters define the bellhousing type and bolt pattern , the shift mechanism , the shaft centers and possibly the syncro type .

None of the early gearboxes (up to the end of R30 production) have any (usable) identifying marks on the outside. The top of the bellhousing just behind the head sometimes has some stamped numbers/letters which might be a serial number, but only Nissan know

servo (Porsche) syncros 1-4 , warner syncro 5th.

Actually the otherway around - warner on 1-4 and servo on 5th, although have seen one or two with warner synchro on 5th. Only 240Z/260Z 5-speeds got servo synchros on gears 1 to 4

240K 5-speeds used the FS5W71B gearbox, but early cars were 4-speed (FS4W71A) and 3.5 diff ratio.

260Z - same as above with closer ratios ie 2.9 1st , aluminium front bearing cover

240Z/260Z used steel front cover, same as 240K. Early 240Z used FS5C71A g/box (flange output; similar to Fairlady gearbox) , late had FS5C71B same as 260Z.

[SLY33]

but so has my friend in his R33 with less power and less Km's.  

So still tossing up wether its worth swaping for a RB25 box....

its an import, you cant use odometer readings to judge anything.

Rb25 box should be just about unbreakable in an quick street driven r32 with an rb20.

[aaronrb25det]

ive just rebuilt my r33 gtst box withe the internals of a grt 32.im waiting to pick it up,wasnt too exspensive ether.should be quite strong

[benm]

Just out of curiosity what did that cost in total and approx how many hours of labour?

[SteveL]

ive just rebuilt my r33 gtst box withe the internals of a grt 32.im waiting to pick it up,wasnt too exspensive ether.should be quite strong

There's no difference in strength between R32/R33 GTR gearboxes and R33 GTSt gearbox.

[mabru]

There's no difference in strength between R32/R33 GTR gearboxes and R33 GTSt gearbox.

Correct, because the part numbers for a majority of the internals are the same between the GTR box and the 25DET box.

[Bl4cK32]

Correct, because the part numbers for a majority of the internals are the same between the GTR box and the 25DET box.

anyone got the part numbers for the main bearings in the r33 box?

[someonestolecc]

Anyone know where the sr20 box fits into this and if a rb25 box mates to a sr20 "bolt in" ?

[SteveL]

.......if a rb25 box mates to a sr20 "bolt in" ?

No...different bellhousing bolt pattern.

[someonestolecc]

No...different bellhousing bolt pattern.

Thanks SteveL - looks like no rb25 replacement for me if my sr20 box dies