Gear Ratio Question

[fdbyrne]

Something odd just happened.

I ordered a new rear 3rd member from ECGS a few days back. They just called me and told me that they think that I ordered the wrong gear ratio. I ordered the 3.90 version. I ordered that one because they, the guys at ECGS, looked up the VIN and told me that that was what my 4Runner had. I also did some of my own research and found that in 2003 and 2004 3.90 wasn't uncommon. I even called the dealership and they verified it which makes sense because ECGS uses the same system they do.

When ECGS called me, they said that they've never rebuilt a 3.90 3rd for a 4th Generation 4Runner. Oddly, the same guy that called me just now was the same one that I spoke to when I ordered. He was the same guy that looked it up by the VIN and here he was on the phone telling me that I had to be wrong and he asked me for my VIN again.

Does anybody out there know for a fact that they put 3.90 rear ends in at least some 2004 V6 4x4 4Runners? I'd really like to only do the job once and get the right one sent to me the first time.

 

[Dominic]

I'm pretty sure all 4-speed automatics, which only come with the V6's had the 3.90 gear ratio, up until 2005 when they got the 5-speed, is when it was swapped to a 3.73.

 

[Troymclure]

Something odd just happened.

I ordered a new rear 3rd member from ECGS a few days back. They just called me and told me that they think that I ordered the wrong gear ratio. I ordered the 3.90 version. I ordered that one because they, the guys at ECGS, looked up the VIN and told me that that was what my 4Runner had. I also did some of my own research and found that in 2003 and 2004 3.90 wasn't uncommon. I even called the dealership and they verified it which makes sense because ECGS uses the same system they do.

When ECGS called me, they said that they've never rebuilt a 3.90 3rd for a 4th Generation 4Runner. Oddly, the same guy that called me just now was the same one that I spoke to when I ordered. He was the same guy that looked it up by the VIN and here he was on the phone telling me that I had to be wrong and he asked me for my VIN again.

Does anybody out there know for a fact that they put 3.90 rear ends in at least some 2004 V6 4x4 4Runners? I'd really like to only do the job once and get the right one sent to me the first time.

Yes they did put 3.91's in 4th gens. I believe only in the early years (03-04) with a V6. If you only have a 4 speed transmission, then you have 3.91's, if you have a 5 speed, 3.73's.

 

[fdbyrne]

Thank you. I was pretty sure myself. I'm just a little surprised that ECGS would tell me that in all of their combined experience that they've never built a 3.91 rear end for a 4runner. Other than Toyota themselves, ECGS probably builds more differentials than anyone.

One more question... the spec for my differential as far as I can tell is 3.909. ECGS says that theirs is a 3.90. Why wouldn't they call it a 3.91 like everyone else? Is it possible that they will actually send me a 3.90 instead of 3.909 and I'll screw something up by running slightly different ratios in my front and rear differentials?

 

[RonJR]

You might want to call and check for sure. The 3.909 would have an 11 tooth pinion and a 43 tooth ring, while the 3.90 would have a 10 tooth pinion and a 39 tooth ring. Both would be considered "non-hunting" and thus are legit values. Ask them which tooth count they are actually using.

 

[fdbyrne]

Thanks. I expressed my concerns and they just reassured me that it would work. I'll call back tomorrow.

 

[Mike07SE]

It's just a more common referral to the gear size. For the 5EAT, the gear ratio is actually a more accurate 3.737. But anywhere you look you'll always see it referred to as 3.73. Same goes with your 3.90.

And to probably speak on their behalf, they probably have never done 3.90's because nobody goes that gear ratio. It was only an oddball size that the factory used for the short term V6 4EAT combo. Pretty much all will go with 4.56 on up (with a few rare 4.11's) since this is usually quite the expense to go through and not want to have regrets with.

 

[Johnny4runner]

I have a 2003 V6 4Runner (4-Speed Auto) and I can vouch that it came stock with a 3.91 3rd. Not sure what the tooth count was, but I assumed that it was rounded to the hundredth. I doubt there is more than one tooth combination available to get close to 3.91.

I thought all V6 were 3.91--even with the 5-speed auto? I could be wrong about that.

I got my new 3rd from ECGS also--of course I went with 4.88 and a truetrac instead of stock. :biggrin1:

 

[Mike07SE]

I thought all V6 were 3.91--even with the 5-speed auto? I could be wrong about that.

This is pretty much the breakdown:

4EAT V6 = 3.91 (3.909)
5EAT V6 = 3.73 (3.727)

4EAT V8 = 3.73 (3.727)
5EAT V8 = 3.73 (3.727)

 

[fdbyrne]

Thanks. They assure me that it'll be right. It should be here at some point this week. I'll count the teeth and bust out my math skills before taking everything apart.

I appreciate the help.

 

[fdbyrne]

I got my new differential from ECGS today. It appears to be the right one. 43 teeth on the ring and 11 on the pinion for a 3.909 ratio. I'm not sure why they call it a 3.90 instead of a 3.91 but it looks like the right setup. It goes on the truck tomorrow.