Input ratio swap

[Tony22]

 I have a L20B engine  and gearbox  from a 910 a (Aussie bluebird ).

i want to swap a pintara gearbox into L20B case/ bell housing 

 

910/bluebird gearbox    Input 22/31   1.409 ratio  3.321    2.077.  1.308.  1:1   0.838

 

Pintara gearbox.             input 21/33   1.524 ratio  3.592.   2.057   1.361   1:1    0.852 

 

if I keep input shaft and counter gear  1.409 22/31 in 910 bluey case and change  too the pintara  gearset  Change the selector from 14mm to a 16mm selector socket too suit 910 case 

i hope to end up with

 

                                        input 22/31   1.409 ratio   3.321.   1.901.   1.257   1:1    0.775 

                                         ......                                                     42%.      34%.   20%   22.5%

 

i only have these 2 gearboxes , the bluey 910 box is stuffed but the input and counter gear are good   So will this work? 

not the standard mongrel box I want,  but 280zx boxes are hard to find here in OZ  and I don't want to spend extra $$$$. 

 

 This is going in a 521 with a 4.625 diff  so the big 1-2 gap 42% give a useable 1st "hard launch" 

and hold to redline before changing too 2nd :)

better to have big gap at lower speed  and ratio's closing up from there 

 

any thoughts ,  idea's , comment's ?  Recommendations  appreciated 

Tony22

 

 

 

 

 

 

Edited May 24, 2019 by Tony22
Typo

[datzenmike]

This will depend on the Pintara 1, 2, 3 gear and over drive ratios. Often two boxes are exactly the same but for the input and the counter driven gear. Here's a mid ratio and close ratio zx box gear sets. If you put the zx input set into the mid ratio you get a mongrel box as shown.

 

 

 

 

 

 

/.

 

 Can you count the first gear ratio and the over drive in the Pinara? These X the 1.4 will give the first and overdrive. There was a '80-'82 zx with a 0.773 over drive.

[Tony22]

Pintara Ca20       first gear   33/14 = 2.357 X  1.52    = 3.592 

Bluey(910)           first gear   33/14 = 2.357 X  1.409  = 3.321

pintara Ca20  5th.OD gear.   21/39 = 0.538 X 1.524.  = 0.82 OD

pintara Ca20  5th OD gear.   21/39 = 0.538 X  1.409. = 0.758 OD :( 

Bluey(910).     5th OD gear.   22/37 = 0.595 X  1.409. = 0.838 OD :)

 

My 100mph mongrel box  swap input from 1.524 with truck #3 / Ca20  > 1.409  should have the following ratio's 

 First.         2nd.         3rd.       4th.           5th OD              

 3.321.      1.902.      1.258.    1:1.            0.758 OD             

Or if you can keep bluey (910) OD gears  

3.321.       1.902.      1.258.    1:1.            0.838 OD 

 

0.775 OD was typo or bad math 

25/28 tooth count for 1.361 3rd gear as pintara box still in car 

with this box I hope to get close to target  under 14 sec 1/4 mile @ 95+mph 

4.625 diff, L20B  in 521  and a bit of motorkana 

please advise if I can do this swap ? 5th OD gears swappable? 

 

[Tony22]

Aussie bluebird is the same a a Maxima L20B  

the pintara is truck #3 or 83-10/84 200sx  with Ca20,

 ratio % change =

               3.321. 42%. 1.901. 34%. 1.258 20%  1:1. OD 0.838. 16% 

215/65/14 tyres 

4.625 ratio diff

speed @6,500rpm= 1, 31mph  2,  55mph  3,  83mph 4th 105mph 5th 125mph

Rpm drop      1-2  3721rpm  2-3 4301rpm  3-4  5171rpm  4-5 5447rpm 

4.889ratio diff

speed @6,500rpm= 1, 30mph  2, 52mph   3, 79mp   4,   99mph . 5.  118mph 

 

Rpm drop between gears is the same with any ratio diff 

now all I need is enough power to achieve it ! ! ! 

 

the original 3rd gear 1.36  is a big jump into 4th  27%  6500-4745

swapped  input  3rd gear of 1.258 into 4th is  20% 6500-5171

this gear set has a big jump into 2nd  although it is 42% that's the same as the standard boxes , a 4.8 Ratio diff will help  get off the line