Alpha 4.10 to 4.56 gears swap strength worries! /Old Man Emu Leaf Spring height ask!

[Guerrero]

Hello Everyone!

I am in the process of building my ultimate Hummer H3 alpha, right now I am focused in axles and suspension..

About gears, I am going to install front and rear factory lockers and maintain the 2.64:1 ratio in transfer case (good ratio for desert driving), my concerns are:

-My opinion is that HUMMER install 4.10 gear ratio in the alpha to reinforced that weak point in the front differential. Lower ratio (for example, 4.56) is weaker than higher ratios....so...why everyone is installing 4.56 gears in off road alphas? I considered doing the swap..till I realize the step back in front axle strength...

-I am currently using 305 70 R16 Toyo Tyres MT so I am considering doing the gear swap to 4.56 because I am in 33 inch diameter. My alpha is right now producing somewhere between 340 and 350 flywheel horsepower, so I should be good with 33 inch, but want to hear your opinions...
another point is, could someone give me some REAL input of how MPG decrease in highway driving from 4.10 to 4.56 gears?

Alpha is amazing but MPG in highway is something that worry me being in Europe and fuel prices here are huge, I like a lot doing long trips and want to maintain my current MPG in highway

-Another separate question to all of you that installed OLD MAN EMU leaf spring; I am considering installing these as I want to replace my current set of leaf spring with OEM, is the same strength and reliability that OEM? Could anyone give some real measurement of how much the OLD MAN EMU leaf spring lift the back? I check other old post but the mesurement dont make sense..
My current Leaf spring measurements front center hub to lower point of fender is 23,3'.....the same that other two h3s from friends. A new set of OEM spring could be somewhere between 23,5' before leaf settle down. How much real height is the OLD MAN EMU leaf spring? (installed in the h3).

Thank you, and hope you could give some light in these!
Guerrero

 

[amrg]

The rear leafs will be 24.5" stock, the arbs sit at 25.5".
As for the gearing, GM dropped to 4.10s to get better economy. Yes, 4.10s have stronger internals over 4.56, but the main issue on the front diff was the case itself, the aluminum on the I5 flexes under torque causing the gears inside to mess up.
Keep in mind, moving to 4.56 will get highway rpms up, but the added gearing torque will mean less throttle input to hold a certain speed/accelerate so less engine load. 4.56 isnt a big change anyway (everyone does 4.56 because its the only option, SAS guys skip to 4.88s)

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[Guerrero]

The rear leafs will be 24.5" stock, the arbs sit at 25.5".
As for the gearing, GM dropped to 4.10s to get better economy. Yes, 4.10s have stronger internals over 4.56, but the main issue on the front diff was the case itself, the aluminum on the I5 flexes under torque causing the gears inside to mess up.
Keep in mind, moving to 4.56 will get highway rpms up, but the added gearing torque will mean less throttle input to hold a certain speed/accelerate so less engine load. 4.56 isnt a big change anyway (everyone does 4.56 because its the only option, SAS guys skip to 4.88s)

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Thank you so much amrg!

Finally found a great deal in a new set of OEM Leaf Spring, new part number #25965051
I installed that set in my previous H3 i5 and handle amazing, seems that all the broken oem leaf spring are the previous part number that comes in all H3s from factory (#15278386).

I broke a leaf pack of this previous part number, installed a new set of the new part number and abused a lot more of it and seems more strength. I get a great deal in a new set so I've gone that route...thanks for the imput in the leaf spring though


About axles, I know that the weakest point is the case itself, being aluminium (aluminium only in the i5, the v8 has cast iron case), and flexing, but 7'6 of front gear set is not a strength axle, and I read a lot that the front axle problem of the h3 is a combination of weak aluminum case allowing flex (only in i5s), and the weak gear set 7'6 represents..(both i5s and v8 have these gear set)
Now considering the alpha with a 5.3 v8 tuned doing 350 hp, I imagine that in hard throttle offroad the 4.10 gear set, with poly bushing kit in the cast iron case will be the most reliable set, dont know either if the gear swap from 4.10 to 4.56 makes a huge difference in power...the alpha is super quick and responsible right now. But despite all of this...I am still considering the swap searching for the most powerful combination :giggle: but I tried to be smart and build in the better powerful/reliable ratio, for a Hummer H3 alpha

About fuel consumption I would love if someone have real numbers from before and after in Highway (with no other mods done except gear swap) if possible..

I experienced that low fuel consumption is directly relationated to low rpm....at highway speeds, the engine can handle the power necessary with minimun load to maintain speed (can do it despite if it is 2400 rpm or 2200 rpm (at 70 mph))....so less rpm means less fuel consumption

Again Thanks a lot amrg and hope to continue launching light over this!

Guerrero
15278386

 

[Jeepwalker]

Am I mistaken? I thought Alphas had cast iron front diff cases ...and the I-5's all had the AL??

 

[Guerrero]

Am I mistaken? I thought Alphas had cast iron front diff cases ...and the I-5's all had the AL??

Yeah that is, I edited my previous comment to avoid missunderstanding, sorry for that!

Alphas have the cast iron diff cases, and all the i5s have aluminium, except the offroad package i5s with front locker in 2009 and 2010, that have cast iron case and 4,56 ratio

 

[Guerrero]

Anybody else's opinions about 4.10 to 4.56 swap considerations of strength?

 

[Bigunit]

I went to 4:56 from 4:10 in my locked Alpha T running 35s. One of the best mods I ever had done. Make sure someone with experience doing this kind of work does it. Reloader did mine and I've had zero issues.

 

[Guerrero]

I went to 4:56 from 4:10 in my locked Alpha T running 35s. One of the best mods I ever had done. Make sure someone with experience doing this kind of work does it. Reloader did mine and I've had zero issues.

Thanks for yout imput Bigunit!

Do you notice worse MPG after the swap? Do you have some record of MPG before and after? Only concerned about highway, i can imagine that in city driving will be equal or better after the swap!

Thanks

 

[JPaul]

I went with 4.56 in my Alpha when I had to rebuild the diffs. It brought the overall gear ratio back to stock when I moved up to 35" tires. Strength is an aspect, but as mentioned it's pretty trivial of a difference when you're talking about such a small difference in ratios. It might be 1 tooth less or more is all. It made a huge difference in acceleration and putting the power band back.

The OME springs definitely push you up higher than the stock springs, they also have a bit of a military wrap at the front eye. I also think they ride a bit better than stock, but that's debatable. Never heard of OME springs breaking. Lots of old, worn out, stock springs break though.