ring pinion 4runner
03-18-2005, 12:06 PM
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ring pinion 4runner
hallo i have 4runner year 1994 . the problem is ring and pinion front axle.
one of the teeth is broken. the orginal ratio is 39:8.
i tried to buy oem part of precision gear and they told me that if i have this ratio original i must buy toyota parts because it will not feet .
toyota parts cost over 500 $.
if someone have experience with this issue i will happy to get advise .
thanks
one of the teeth is broken. the orginal ratio is 39:8.
i tried to buy oem part of precision gear and they told me that if i have this ratio original i must buy toyota parts because it will not feet .
toyota parts cost over 500 $.
if someone have experience with this issue i will happy to get advise .
thanks
03-18-2005, 01:21 PM
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Can't even think of a typo that could be (3.889, 3.9 etc) 3.9 is in 2wd autos, never knew what supposedly came with 3.889s.
I know of no front ratio that is not commonly available aftermarket, but there are a few pitfalls to certain rears. None of them is 39.8 though. Try this: http://www.off-road.com/toyota/tech/other/4_axles.html and scroll down to the chart.
I know of no front ratio that is not commonly available aftermarket, but there are a few pitfalls to certain rears. None of them is 39.8 though. Try this: http://www.off-road.com/toyota/tech/other/4_axles.html and scroll down to the chart.
03-18-2005, 01:44 PM
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Ahh Yes.. I have been through this one.
The reason you are unable to get aftermarket gears for your original 4.88 front axle is because the ring and pinion spacing is completely different in these axles. Assuming your 4Runner is an auto, just as my truck is, 4.88's were common..
When you go with lower gears, say from 4.10's to 4.88's for example, your pinion gets smaller and the ring gear gets a little thicker. With a smaller pinion, at any given time, you have less gear mesh than with a larger one or taller gears. It is for this reason that you can only go so low with your gears before they start to become to weak.
As a result, when toyota designed the 4.88 gears at the factory, they increased the spacing between the ring gear and the pinion gear, thus strengthening the gears and still allowing the 4.88 ratio. If you tried to put standard aftermarket gears in your diff they would not mesh. On the rear you can simply swap out your 3rd member with one that came with 4.10's factory and purchase aftermarket gears. For the front I am not sure. May have to swap out the entire center section. At least you have the peace of mind knowing that your factory 4.88's are stronger than the next guys aftermarket, but not strong enough in your case.
However, I have heard, that another way around this is to purchase one of the gearless lockers. I have not tried this to verify.
This is the reason I still have my factory 4.88's in my truck as well.
The reason you are unable to get aftermarket gears for your original 4.88 front axle is because the ring and pinion spacing is completely different in these axles. Assuming your 4Runner is an auto, just as my truck is, 4.88's were common..
When you go with lower gears, say from 4.10's to 4.88's for example, your pinion gets smaller and the ring gear gets a little thicker. With a smaller pinion, at any given time, you have less gear mesh than with a larger one or taller gears. It is for this reason that you can only go so low with your gears before they start to become to weak.
As a result, when toyota designed the 4.88 gears at the factory, they increased the spacing between the ring gear and the pinion gear, thus strengthening the gears and still allowing the 4.88 ratio. If you tried to put standard aftermarket gears in your diff they would not mesh. On the rear you can simply swap out your 3rd member with one that came with 4.10's factory and purchase aftermarket gears. For the front I am not sure. May have to swap out the entire center section. At least you have the peace of mind knowing that your factory 4.88's are stronger than the next guys aftermarket, but not strong enough in your case.
However, I have heard, that another way around this is to purchase one of the gearless lockers. I have not tried this to verify.
This is the reason I still have my factory 4.88's in my truck as well.
03-18-2005, 06:34 PM
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Originally Posted by Silver_Truck
Is 39:8 the same as a 4.88:1? If so you should be able to get any aftermarket gear you want and put it in
39:8 is the ratio of teeth on the drive gear to teeth on the driven gear. 39 divided by 8= 4.875 or rounded to 4.88.
03-19-2005, 09:40 AM
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NO. 4.88 FRONT GEARS ARE NORMAL. Any aftermarket gears will fit. The REAR gears are different and you're stuck there.
I have aftermarket front 5.29s in my front.
http://www.pirate4x4.com/forum/showt...highlight=4.88
I have aftermarket front 5.29s in my front.
http://www.pirate4x4.com/forum/showt...highlight=4.88
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03-22-2005, 10:40 AM
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Robinhood is right. Factory 4.88s (8" r&p) have a different carrier in the rear. All the fronts are the same. Lotsa threads here and tech articles on the net about this.
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