# gear ratio on rear end



## z-family (Oct 2, 2004)




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## hatcityhosehauler (Feb 13, 2004)

I think a couple of folks here have done it. I seem to remember them saying it was between $600-$800 upgrade depending on the parts purchased. One thing to remember is that if you have a 4x4, then you must change out both differentials, doubling the cost.

Tim


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## vdub (Jun 19, 2004)

I have asked my Ford dealer this question. Yes, it can be done and it costs double for a 4x4. Cost on my F-250 would be about $2500. Although it will make a difference on what you can pull, it does not make a difference on what you can pull legally -- at least, according to my dealer. If the differential is changed, you do not get a new sticker with new GVWR, GCWR, etc. Seems odd that would be the case, but apparently it is. If you find out differently, please let us know.


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## z-family (Oct 2, 2004)




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## vdub (Jun 19, 2004)

Uh, yeap.... That was my conclusion as well....


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## Y-Guy (Jan 30, 2004)

I am pretty sure that California Jim did this and posted a report, might do a search on Eaton and see what you pull up. The dealership was really high in price but CJ found somebody else that was much cheaper as I recall.


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## California Jim (Dec 11, 2003)

Hello Z:

My Brother in Law changed out the grears on his 1999 4X4 Suburban and also had all the bearings replaced for $1200. You shouldn't pay much more than $600 per axle to do this job. I think you would notice a BIG difference going from 3.42's to 4.10's, and a more minor but still noticible difference going to 3.73's.

Given my experience with a trailer of similar weight, and the same engine I would highly reccomend the 4.10's. Our 1/2 ton trucks are near the top of their towing capacity and working very hard in the hills.

Best of luck with whatever you decide


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## z-family (Oct 2, 2004)




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## shake1969 (Sep 21, 2004)

I read where you can do a "poor man's" gear change by adjusting your wheel/tire size. I suppose smaller wheels/tires would increase the ratio, ie; more tire revolutions/driveshaft revolution @ the tire patch. Or is that larger wheels? I get confused.

Anybody know this formula?


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## California Jim (Dec 11, 2003)

I don't have the formula handy, but that's true. Although I have changed my gears from 3.73 to 4.10, I am rolling on aftermarket 20" wheels and my tire diameter is 2" taller than stock. Last time I calculated it my "effective" ratio is right back at 3.73. I know it's right also because my speedo is correct again after changing the gears.

So yes, smaller diamater tire than stock = numerically higher gear ratio.
Larger diamater tire = numerically lower gear ratio.


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## JimWilson (Feb 24, 2004)

California Jim said:


> My Brother in Law changed out the grears on his 1999 4X4 Suburban and also had all the bearings replaced for $1200. You shouldn't pay much more than $600 per axle to do this job. I think you would notice a BIG difference going from 3.42's to 4.10's, and a more minor but still noticible difference going to 3.73's.


Generally, going from something like 3.42's to 4.10's also requires upgrading the carrier as well, something that isn't usually necessary when going from 3.42' to 3.73's.


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## camping479 (Aug 27, 2003)

Will going from 3.42's to 3.73's make much difference?

I've debated back and forth and so far the general consensus seems to be it's not worth the expense. The trailer is less than 5k loaded and the yukon does a pretty good job. We'll probably trade it in 2 years, so I don't know, I don't want to waste the transmission, don't know what to do.










Mike


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## hatcityhosehauler (Feb 13, 2004)

Here is a handy page with a bunch of calculators on it.

4 LO gear calculators

Unfortunately, I don't know if there is a comparision of LT's. I only see a converter for P-Metrics to inches.

Tim


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## johnp (Mar 15, 2004)

You can also go to ringpinion.com Randy's has some good calculators I had a 97 burb with the 5.7 and 3.42 it pulled the 26rs ok but watch that tranny. I bought front and rear 3.73's to put in it but when tranny number two started to give me problems I dumped it for the beast in my sig. The gears, mirrors and a westin brush guard may soon be on ebay.


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## jscotb (Apr 10, 2004)

I just had 4.10 gears put in my Avalanche. The bearings went in the







differential, so while they had the thing apart - New Gears!

Just got back from my first tow with the new gears, big difference. I did not think it would make as big a difference as it did. I had 3.73, so not a big step in the ratio. It really changed my attitude towards my Avalanche as a TV. Gas mileage has not changed much either, not appreciably. Happy for now with AV pulling 28RSS.


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## California Jim (Dec 11, 2003)

Sweet!


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## hatcityhosehauler (Feb 13, 2004)

If you don't mind my asking....how many miles were on the Av when the rear end bearing went? I had my Av at the dealer for some minor warranty work a few weeks ago, and had them do a LOF and other routine maintenance since it was due. I asked about the differential fluids, and was told, don't worry about it. I even explained that I tow a 5000+# trailer most of the summer, and he still said "don't worry about it, they changed to a synthetic oil in the differentials. You should be fine."

Needless to say, after reading your post, and one or two others, I think I may crawl under and check the fluid myself!

Tim


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## jscotb (Apr 10, 2004)

My AV had 45,000 miles. I do not think it has anything to do with the fluid. The bearings disintegrated. The mechanics that repaired said the bearings had not been hot, probably inferior quality. I am a member of the Avalanche Forum and there are lots of people with rear differential problems. I got a call from Chevy customer service and they apologized for my problem, thatâ€™s all. I had the rear fixed by an independent, not Chevrolet, so they are blowing me off. The Chevy dealer said out of warranty, your problem. They also wanted $1100 to repair the bearings only. I like the Avalanche, but it is my last Chevrolet. They have a big problem that they are ignoring. Listen out for whining noises that sound like a tire noise, thatâ€™s how mine started. Hope I didnâ€™t vent to much, but this is a issue Chevrolet needs to deal with.


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## JimWilson (Feb 24, 2004)

camping479 said:


> Will going from 3.42's to 3.73's make much difference?
> 
> I've debated back and forth and so far the general consensus seems to be it's not worth the expense.


I would concur with the general consensus; going from 3.42' to 3.73's is probably not worth the expense and hassle. If you have 4wd, which means you need to do the front and rear diffs, then it's really hard to justify. Now, if you're in dire need of some improvement, and you're going to keep the truck/trailer combo for a while, then maybe it's worth considering. But given your circumstance it sounds to me as though it's not the best thing for you to do.


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