No power after change of Gearbox

[dwambua]

My car is a '97 BG5 - Twin cam Non turbo. I replaced my original gearbox with a used one (Ex Japan). I was unable to get an exact match of the original one and got a replacement that matched on the first six characters only.

Problem is after the replacement, the car is moving alright but you do not feel its power. Got someone to carry out a diagnostics check today and he suggested i change the computer as it was reporting of incompatibilities.

 

His explanation is that it appears apparent that there is lost communication that is causing the car not respond as required.

 

What do the experts here recommend? Is it possible i can get a computer that is compatible with the gearbox but not the engine? Is there a work around to ensure the existing computer can work with the gearbox and engine to enable me get the output i so desire?

 

Will appreciate your help.

[Brighton96]

It sounds like the trans gearing is different then the old one, it may just be a mechanical difference then an electronic one. Did you swap the diff and trans or just the trans? Just because the diff ratio is the same doesn't mean the rest of the gearing is, but the computer wouldn't/shouldn't care that much about gearing I would think.

[Infosecdad]

What are the full numbers (trans code) of each tranny?

[Setnev]

First off, is it a gearbox (5MT) or a slushbox (4EAT)? I ask because you said someone told you to swap ECU due to "inconsistencies". 5MT is not computer controlled, nor is the transmission dependent on a computer, other than for the speed sensors.

 

Second, JDM manual transmissions for that vintage and model are almost always 4.444 final drive. Other markets (US, EU, AU) got a 4.11 FD, or worse, a 3.90 final drive because they provide better fuel economy for longer hauls typically encountered in those markets. Most JDM cars will be lucky to see the freeway speeds we encounter on a regular basis, so they're geared for more low RPM performance.

 

As Brighton asked, did you swap the rear diff or even make sure that your existing diff was compatible with the transmission? If not, you're very likely going to suffer catastrophic failure of your rear end, center diff, and/or transfer gears. We need to know what the full part number is off both of the transmissions.