37s with an I5 auto How bad can it be?

[06 H3]

How bad can it be?

I am currently running 35s with a catback exhaust, air doc and an AFE pro dry filter, thats it. stock 4.56s after running hammers I realized 35in goodyear duratracs are not ideal for this. I need MTs and to go bigger.

I am running no PCM tune, do u guys think a PCM tune with 37s would cancel out how it currently drives? Supposedly it makes a big difference and I have been driving tuneless for years.

As for strength I will be running probably the strongest AAM-7 you can run with cryoed gears and all the works. Just waiting to install the locker.

I still have 35-40% tread life left so I will wait a bit longer and I will stay with a 16in rim so that leaves me with the 345/75/16 KM2 or the 37x12.5x16 IROK radial, not sure if there is anything else.

The solid axle I picked up is gonna be a while. I need a DD seeing downtime will be a while, I think I am going to get my bike license and drive around on some old cheap POS street legal 250cc dirt bike.

I picked up the axle on a deal, and need to still get mounts and brackets but I am still not 100% convinced. I feel more pressured as its the "cool thing" to do with the rock crawler crew. Over the next few months I will push this IFS to the limits with more hammer trails if I can get back out there soon. I remember feeling somewhat like this with the spring over, I did it and I would never go back. I am scared on the SAS but if I do it I feel I will love it but at the same time I hate the fact that I am not pushing my IFS further. I try not to seek opinions too much because its what I drive everyday not what other people drive but when I dont know what I want I entertain the ideas of others. I have some tell me the IFS hasnt held me up yet, just slowed me down so continue with it and others say chop it off.

So for the time being while I atleast get brackets and try to have an axle "H3 ready" I will throw some 37s on and see how long it lasts.

 

[06 H3]

I am more interested in street performance. I know 37s will do work off road but on road is the question....

I wonder if 35s, no PCM tune will be the same as 37s with a PCM tune and maybe a header.

 

[Kyle]

i honestly think you should go with a pcm tune and do as much as possible to get some power, maybe even re gear, what i would do is drive up the grapvine with the 37s on and see how things go, if you can tackle the grapvine without having to have the truck floored and in 3rd gear then id say your golden.

 

[06 H3]

regear is not possible with an AAM-7. I think I would lose 3rd gear up the grapevine and have to hold it between 2nd and 3rd. 4th would be useless.

 

[4speedfunk]

How bad can it be?

Bad enough to ignore the "D" and go straight to "3" every time you put it in gear. :giggle:

 

[06 H3]

I know the 5.13s would solve that problem...

 

[Kyle]

regear is not possible with an AAM-7. I think I would lose 3rd gear up the grapevine and have to hold it between 2nd and 3rd. 4th would be useless.

more power then, 37s are going to make the thing a total dog on the road imho, unless you do an axle swap and re-gear to get back into the power band and have some more power behind the I5. whatever happened to doing a cat delete? Maybe even a whole new exhaust system to free up some more horsepower, im talking from headers back just do a whole new exhaust system with high flow headers, high flow cats, and high flow everything else.

 

[Kyle]

i really think the good ol I5 has potential to produce some decent power, they used the i5 in the h3 they ran in BAHA

 

[atvspeed4]

If I was going to keep the H3 I would have put 37s on it. I really dont understand the whole "underpowered" thing everyone bitches about. My last two H3s have been on 35s their whole life and I pull a 3800lbs snowmobile trailer to NH in the winter. In the summer I have 5 people in my H3, a roof basket, spare tire basket and trailer hitch basket full of camping gear and have no problem on the highway going 65+. At the mountains I might drop down to 50 but that is to be expected. Sure there will be long steep stretches of highway that you are going slow but who cares we dont drive racecars...

I say do it

If you think our rigs are slow you have never been in an H1.

 

[06 H3]

your selling the 3?

37s here are tough because we have speed limits at 65, strong headwinds, and steep climbs.

 

[atvspeed4]

your selling the 3?

37s here are tough because we have speed limits at 65, strong headwinds, and steep climbs.

Possibly this Friday not sure yet. Our speed limit is 65mph too.

Just do the 37s you will be happy you did.

 

[Kyle]

If I was going to keep the H3 I would have put 37s on it. I really dont understand the whole "underpowered" thing everyone bitches about. My last two H3s have been on 35s their whole life and I pull a 3800lbs snowmobile trailer to NH in the winter. In the summer I have 5 people in my H3, a roof basket, spare tire basket and trailer hitch basket full of camping gear and have no problem on the highway going 65+. At the mountains I might drop down to 50 but that is to be expected. Sure there will be long steep stretches of highway that you are going slow but who cares we dont drive racecars...

I say do it

If you think our rigs are slow you have never been in an H1.

Have you ever driven on the freeways here in California or Los Angeles area? lol in order to drive on the freeways here and not be run of the road by a bunch of pissed off drivers doing 85 you need to be able to keep up with the flow of traffic somewhat. the speed limits on the freeways here say 65mph but everyone some how thinks that the sign is a suggestion and do 10-15mph over it.

 

[freeze]

Based on how ATV drives that 3 with 35s, I would say 37s would be no problem at all. 10-15 over the limit is Cake with the 35s. I've seen him pull trailers right up to the weight limit, and still haven't been able to keep up in my Hummer.

 

[06 H3]

Your a manual though? That will help too ill probably try it anyways

 

[Mb30sdl]

Then regear transmission. T is pretty slow going up 10% hill pulling small trailer and 3 people. I was stuck doing 30-40mpg in 2nd gear. When it shifts to 3rd I loose all the power and can't shift down till it slows down to ~30.

 

[rsc]

There IS one tire you could mount that might help out a little in the power dept, Falkken makes a metric 36.5" tire for a 16" rim. Its an AT though and its a Falkken too, probably not what you are looking for but it would take less power to spin than a KM2 or IROK. I would bet that going to 37's on an I5 gets you about 10 mpg in 3rd and that 4th would be totally useless unless you went with all the power bumping goodies like the efan/header/exhaust/ported throttle body/PCM tune. That might just be enough to let you run 4th on flat highway. The only re-gearing I've seen for the 4L60E is for the 1-2 shift, not 3rd or 4th gear where you really need it. A PCM tune would really help with shift points and holding gears longer, but can't overcome the insanely high gearing in 4th. Remember, 3rd is 1:1 and 4th is some horribly high 0.67:1 overdrive ratio. Third on 37's should put you in the middle of 3rd/4th on stock-ish tires.

 

[Kyle]

maybe just straight trans swap Chris? lol get an 8 speed and stuff it in there! :mock:

 

[Mb30sdl]

GearVendors probably can make it. Doing some research for f350 I can get secondary transm that will give me 3.5 and 4.5 gears.so 6gears instead of 4.

 

[Kyle]

GearVendors probably can make it. Doing some research for f350 I can get secondary transm that will give me 3.5 and 4.5 gears.so 6gears instead of 4.

probably will cost a pretty penny though!

 

[Zach]

Then regear transmission. T is pretty slow going up 10% hill pulling small trailer and 3 people. I was stuck doing 30-40mpg in 2nd gear. When it shifts to 3rd I loose all the power and can't shift down till it slows down to ~30.

If you did that, wouldn't you also have to regear the tcase? I know with the change in 2's the tcase is different because of the trans. Not the engine. It's how it's geared I believe. If not, please enlighten me.

 

[mudbug]

Could be wrong but I don't think the tcase cares what speed the shaft from the transmission turns.
I know they are bias ply but you could look at 36" iroks they are the same size as the 37" radials.
What auto trans does the H3 use?

 

[Zach]

Trans is 4l60E. I know the 2's went through the change in 08. Not that familiar with them. I know the tcase changed gearing then.

 

[amrg]

Without regearing wldnt the transmission b extremely unhappy with 37s?

 

[Mb30sdl]

Isn't TC just 2:1 or 4:1 drop in output? If so transmission regearing doesn't affect it, besides making LOW gears even lower. So if you have 2:1 drop TC with lower transm. gear it will be 3:1 or so.

 

[4speedfunk]

Just do the 37s you will be happy you did

True, as long as you just cruise around town.

But if you do any high-way driving at all....37"s will quickly turn your H3 into the most annoying vehicle you've ever driven. It will NOT stay in OD and it will constantly hunt between 3rd & 4th gears. 65mph is awful...70mph is so-so...75mph is finally fast enough to keep the truck in 4th gear on level ground. But any headwind or slight uphill grade will cause a downshift to 3rd (and sometimes 2nd)...which results in a 5000rpm charge to maintain speed. Cruise control is practically useless when a vehicle is this under-geared. Even with a ECM/TCM tune and an Airdoc...it's a huge compromise on drive-ability. If you run a stripped-down H3, the hit is not so bad...but if you frequently travel the interstates with passengers, camping gear, or a trailer...forget it.

Off-road its another story. 37"s are great! You need the 4:1 t-case to really put them to work, and they make a difference on the trials especially when crossing large obstacles. The big question you gotta ask yourself is: Is it worth the huge hit in drive-ability for this gain in offroad performance? IMO...no. 35"s only sit 1-inch lower, so learn to work with them, until you can afford the re-gear (SAS).