BJ73 Differential

[Izee]

Hi,
I'm new to this forum. i have a BJ73. i put in a 5 speed manual gear box now i have a lag on speed on the 5th gear. what should be the differential. i think whats on the jeep is 37/9. is this correct or what should i have to correct the issue.

Thanks
Izee

 

[Hulsty]

Turbo, more power.

 

[sadam_husain]

as above you need more power or lower gearing, the body plate on the firewall should have the diff code on it to work out the ratio but you'd really need to pull the diffs to physically check them to be certain of the ratios as they could have been swapped over by a pervious owner during the past 20+ years

translation of the diff codes here
http://www.cruiserfaq.com/09-01.php

 

[Izee]

Thanks.
The issue is it has not got a plate. The engine 13bt witch came with a Auto transmission. The gear box has been changed to a 5 speed manual supposed to be from a 14B engine. need to now what is the 39/9 teeth ratio is correct or what should it be.

 

[Hulsty]

If it has a 13BT, manual and 4.11 diff gears you should have more than enough headroom for more power to drive it. That is the setup I run with 35'' tyres and lots more boost than stock, goes well.

 

[cruiserdan]

If it has a 13BT, manual and 4.11 diff gears you should have more than enough headroom for more power to drive it. That is the setup I run with 35'' tyres and lots more boost than stock, goes well.

How much is "lots more boost than stock"?

 

[Hulsty]

Currently at 24psi boost, putting out around 100-120kw at the wheels, somewhere around 500-550Nm torque at the engine estimated.

 

[cruiserdan]

Nice. I presume there is much more to it than simply cranking up the boost that high. Seeing as stock is about 8 psi max. I imagine fueling at the very least.

 

[Hulsty]

Yeah, a Gturbo CT26, 3'' exhaust, smaller cooler and fuel pump wound up to the max.

 

[cicak]

Thanks.
The issue is it has not got a plate. The engine 13bt witch came with a Auto transmission. The gear box has been changed to a 5 speed manual supposed to be from a 14B engine. need to now what is the 39/9 teeth ratio is correct or what should it be.

This should have way more than adequate power mine ran for years with this combo before we rebuilt and modified the turbo and fuel pump and timing gear similar to hultsy's but a few more mods. I ran 8/39 DIFF ratio (destroyed that) and now 9/41 or 10/41 I forget as I just put new crown and pinion in rear after another bolt came out and took the crown out.

Are you sure turbo has proper boost (8psi), injectors are fine (cleaned) and fuel pump is fine, Fuel filter is not blocked. Does it smoke badly. What is the EGT temps? is it underfueling? haveyou taken to a diesel specialist to see if the basics are set corrrectly.