Just bought a new 4.0L

[Firebird]

Hi everyone, I just bought a 94' Mazda B4000. It has the same engine as the ranger, so I wanted to ask some questions here. First off, this thing wont rev over about 3000rpms, any idea why? It feels like it just wont get any fuel past that point.

Second question, is there a write up, or does anyone have a walk through on changing the gears in the front axle?

Thanks for any help, I look forward to any help I can get.

 

[Wicked_Sludge]

welcome to the boards.

more then the engine is the same between your mazda and a ranger, if you lifted the body off of both, you wouldnt know which was which.

what does the engine do when you try to rev higher then 3k? does it sputter and stumble? or does it just rev up to 3k and stay there?

setting up a ring and pinion isnt as simple as throwing the gears in and going. it takes some special tools and special skills to know how to set them up properly. HERE is a good article on R&P setup.

 

[Firebird]

Thank you very much for your reply.

As for the rev problem, it depends on the gear, in 1st it just revs up to 3K and stays there, same in with the clutch in. In 2nd and higher it does the same thing but stumbles a little. Any ideas?

Thank you for the article on the axle, looks like I better do my homework before I jump into it.

 

[Wicked_Sludge]

as always, start with checking basic tune-up items. check spark plugs, wires, and fuel and air filters. you might try pulling codes on it. even if the CEL isnt on, there may be codes stored in the PCM that could help point us in the right direction.

 

[woodyedmiston]

You might try something real basic first - pull the hose to the air cleaner (air channel) off and see if you are getting full open throttle when you depress the pedal.

 

[MAKG]

The best ring & pinion setup article I've seen is Randy's. http://www.differentials.com/install.html

They really are all just about the same. And it is NOT easy. You have to be really anal about the settings or your gears won't last.

The easiest way to swap gears in the front is to swap the whole front pig.

 

[Bob Ayers]

Thank you very much for your reply.

As for the rev problem, it depends on the gear, in 1st it just revs up to 3K and stays there, same in with the clutch in. In 2nd and higher it does the same thing but stumbles a little. Any ideas?

Thank you for the article on the axle, looks like I better do my homework before I jump into it.

The PCM has a rev limiter, as well as a speed limiter. If you are driving, the RPMs will go higher than 3K, but not sitting still with the clutch pushed in.

 

[fastpakr]

The PCM has a rev limiter, as well as a speed limiter. If you are driving, the RPMs will go higher than 3K, but not sitting still with the clutch pushed in.

Since when does the ECM limit engine speed on a manual transmission vehicle based on the clutch safety switch? It certainly doesn't on my '94. It may on an auto in neutral/park, but not on the manual transmission vehicles.

 

[MAKG]

The best ring & pinion setup article I've seen is Randy's. http://www.differentials.com/install.html

OK, I take this back.

Randy's is definitely usable, but I read the Pirate article, and it's very well written and the figures are amazing. It particularly shines with the gear marking interpretation. Randy's discusses this in detail, but the figures are not easy to read.

 

[Bob Ayers]

Since when does the ECM limit engine speed on a manual transmission vehicle based on the clutch safety switch? It certainly doesn't on my '94. It may on an auto in neutral/park, but not on the manual transmission vehicles.

You may be correct, I thought the rev. limiter came into play with the clutch disengauged also.

 

[Wicked_Sludge]

You may be correct, I thought the rev. limiter came into play with the clutch disengauged also.

its a moot point because a '94 doesnt have a nuetral rev limiter anyway. the rev limiter is about 6500 on his truck, whether its in motion or not.

 

[Bird]

You may be correct, I thought the rev. limiter came into play with the clutch disengauged also.

No Bob, you were correct - the later models all have a 3000 rpm rev limiter when in park (auto) or neutral (auto/manual). A good tuner can take it out, but for a daily driver, why bother.


Bird

 

[Wicked_Sludge]

yep, starting in '95.

since this is a '94, it doesnt matter.

 

[Firebird]

Thanks everyone for your replies. I actually bought the truck last night, so I didn't get to test it out very well. Tonight I took it for a drive and noticed it would rev all the way to redline as long as i didn't go over about 3/4th throttle. So I figured maybe the throttle position sensor might be bad. Sure enough, I unplugged this:
http://picsorban.com/upload/dsc00044.jpg
Which is what I thought was the right one, and the truck revs straight up in gear now at full throttle. Does anyone have a part number for this? What are the adverse affects of just leaving it unplugged? It feels a little sluggish now.

For the gear question, I have an almost full front axle sitting in the bed with the original gearing, please look at these pictures.
http://picsorban.com/upload/dsc00046.jpg
http://picsorban.com/upload/dsc00049.jpg
http://picsorban.com/upload/dsc00047.jpg

It has 4517 stamped on it. It looks like the center differential could be disconnected from the axles and main housing which acts as the cover, and be directly bolted into my new one. If so, this would be great so I wouldn't have to set up the gear and pinion myself.

Thanks again everyone for your help, I look forward to ANY info I can get.

 

[Wicked_Sludge]

good call. thats a bad throttle position sensor. any of your local parts stores should be able to get one for you at a reasonable price. unplugging it should have tripped the CEL...which means your truck is now running in open loop. it'll hurt your power, mileage, and overall dirveability.

your right about the differential being removable from the main housing. thats the easiest way to swap in new gears. you need to match them with the gears that are already in the truck, however, or else your 4wd will be very much useless. if you have the passenger side beam that matches the drivers side one (pictured), then it should have a large plastic sticker on it that will tell you the gear ratio. if not, you'll have to pull the diff. off and count the teeth.

to determine the current ratio in the truck, you can read the axle code off the drivers door sticker and compair it to the codes in the tech library.