I have decided to change the gears in my suburban (2008 5.3L 4sp auto), but not sure how much of a change to make. I currently have 3.73 gears, and was thinking 4.30 because 4.10 doesn't change much, and 4.56 may be a little too much. I have read many accounts where people thought it was great, some where people wish they had gone more, but never of someone wishing they had not changed anything. Has anyone here changed their gears and regretted the decision? If so why? Anyone think 4.30 is the wrong choice?Last but not least, just to be clear, I am NOT trying to save on gas by changing gears. I do not plan on ever getting my money back, just trying to give my suburban a little boost in towing power.

Here is a good rpm calculator if you want to know what rpms you will be at in each gear at certain speeds. May help you make a decision. RPM Calculator

Thanks ShinerBock, I didn't think to look for one, I just channeled my inner nerd and made one on excel. Would have been easier, but not as fun to use that one.

Are you having little issues (move to 4.10 appropriate) or big issues (4.30 appropriate)? Issues getting underway? Climbing?

Seems to me like a lot of investment for little payoff. I tried making mods to my half-ton Burb, and in the end I decided to upgrade to a 2500. THAT was the best choice I ever made, not re-gearing my half-ton.My '01 Burb had the 4L60 and 4.10 gears. I always towed in third, and the engine was around 3200 RPM at 65 MPH. I towed down to Florida, and out to the Rockies over the Continental Divide. Engine didn't have enough power/torque to hold speed in O/D, plus I didn't want to overstress the transmission. Third is a 1:1 ratio, so the tranny was just passing the power through. Regearing to a 4.30 would provide negligible increase in power, but increase your RPMs. And also, you still have that weak 9.5" semifloater rear, which, IMHO, is the weakest part of the powertrain. If you're towing something approaching 6,000-7,000 lbs, an upgrade to a 2500 would be your best bet.Just my $.02.

If it is HP and torque that you want why not just go with a different tow vehicle with the engine and tranny and rear end that will cover you now and anything in the future. Those combinations are out there but you got to lay out the bucks to get them.

Changing the gears in my suburban | Good Sam Community

LanceRKeys
Explorer
Nov 09, 2017
I tow a 26' KZ spree, but it is closer to 30' overall length
Ready to camp:
Steer Axle: 2960lb
Drive Axle: 3700lb
Trailer Axle: 5200lb
Gross Weight (truck+trailer): 11,860lb

All weights are within the specs of the suburban, per my stickers.

I have added a large after-market trans cooler. And I will change the trans filter and fluid in the next month or so.

The Burb is STABLE going down the road, a very enjoyable ride, even when in traffic around semis or during heavy cross winds.

All good comments and I appreciate the conversation. I have thought about getting into the motor, but this is my wife's daily driver and I don't want to do those kinds of modifications (supercharger) for her to drive around and sit in the pick up line at school everyday.

I don't mind the comments to purchase a 3/4 or 1 ton, or even the comments to buy a diesel from time to time. If we stuck strictly to the topic at hand, the discussion wouldn't be nearly as entertaining.

I am still shopping for a dedicated tow vehicle, but it is going to have to be just the right vehicle for a good price, those don't come around all that often and sometimes the search could take a while, until that time, I will continue to tow with the suburban.
jbeliera
Explorer
Nov 09, 2017
falconbrother wrote:
My 4x4 burb has the same gearing ratio with a 5.3. When not towing it runs super strong. Will burn the tires. But, towing isn't real impressive. I'm never going to change gear ratios. I'll live with it till I can buy a dedicated tow vehicle and keep driving this burb to work every day. That's going to be a couple of years away. The good news is that the 5.3 doesn't mind RPMs as much as I do. I do a drain and fill of my transmission at every oil change to keep the Dex6 nice and red. I changed the filter a few months ago. Nevertheless, the burb is adequate for towing. It really depends on what your standards are. Years ago I towed TT's with vehicles that didn't do as good as the burb.

Good boy taking good care of your Burb
falconbrother
Explorer II
Nov 09, 2017
My 4x4 burb has the same gearing ratio with a 5.3. When not towing it runs super strong. Will burn the tires. But, towing isn't real impressive. I'm never going to change gear ratios. I'll live with it till I can buy a dedicated tow vehicle and keep driving this burb to work every day. That's going to be a couple of years away. The good news is that the 5.3 doesn't mind RPMs as much as I do. I do a drain and fill of my transmission at every oil change to keep the Dex6 nice and red. I changed the filter a few months ago. Nevertheless, the burb is adequate for towing. It really depends on what your standards are. Years ago I towed TT's with vehicles that didn't do as good as the burb.
mkirsch
Nomad II
Nov 09, 2017
Recommending an upgrade to a 3/4 or 1 ton truck is "offensive" but apparently it's acceptable to recommend an expensive engine overhaul and blower?

The gearing change is relatively easy and inexpensive, especially if the OP can DIY it, but an engine overhaul and blower kit is going to run you SEVERAL THOUSAND DOLLARS if not more.

Even after that expensive overhaul and blower, he still has a 1/2 ton transmission, a 1/2 ton driveshaft, a 1/2 ton rear axle, 1/2 ton springs, 1/2 ton frame. All of that needs to be upgraded to handle the extra power from the blown engine, and he may still need the gearing change after all is said and done.

People consider gear changes because they feel there is a deficiency in their tow vehicle. That deficiency is in power. That deficiency is caused by a heavy trailer, which while it may not exceed any limits on paper, is still a significant load on the truck that could be handled better by a heavier duty truck.

Heck, at page 6 I don't even think we've ever been told what trailer he is towing, or what it weighs! Yet the "Anti-3/4-Ton Police" are here in force shouting down anyone that dares recommend upgrading the whole truck rather than just the axle gear ratio.

But again, it's perfectly fine to tear the engine apart and put a friggin' BLOWER on it?!?!?

Ultimately, it is the OP's choice, and it does not hurt to have all the options laid out on the table. Maybe, just maybe, the OP will see something that he had not considered before?

...but nawwwww, let's just shout down anyone that doesn't answer the OP's questions exactly as asked...
4x4ord
Explorer III
Nov 09, 2017
Have you considered rebuilding your engine? You could install a stroker kit or a supercharger, either of which could dramatically effect your towing performance.
mt1729
Explorer
Nov 09, 2017
3.73 is a good overall gear ratio. What you lack is power. Tow in a lower gear when necessary or get something with more power. Just my opinion for what it's worth.
Huntindog
Explorer
Nov 09, 2017
BenK wrote:
There is a potential weakness in the higher numerical gear sets because the pinion gear get pretty small in dia vs the ring gear..

I have read that the reason the GM Dmax only comes with a 3.73 is that in testing, the lower gears would not hold up.
The pinion has less tooth area in contact with the ring gear... That is the issue.

In spite of this, I feel it is a worthwhile mod for some.
It will perform better, and as long as the usage is low, will likely be trouble free. That covers a lot of people.

For those that tow heavy and often.... A half ton will always be just that.
BenK
Explorer
Nov 08, 2017
Go for it...another learning experience of school of hard knocks...not saying you won't like it...think you will...but it will still be a half ton...

Know from my hard knock PhD's...

My 1973 K5 Blazer was not up to the trailers borrowed from buddies...even though they were in the 18' to 24' range. Short wheel base and that half ton frame...need the whole package to manhandle the situation at that day Mr Murphy cross your path...

Took a few weeks scrounging and another few weeks installing a Dana 60 front (re-arched with positive curve) and GM 14 bolt rear. Up sized all the U-joints, etc, etc to a full 1 ton suspension...but...it was still a half ton frame...

There is a potential weakness in the higher numerical gear sets because the pinion gear get pretty small in dia vs the ring gear...but...it makes up for it with more turns per rev to distribute the torque over the ring gear.

As others have stated...your tire rev's per mile will come into play, as are the other attributes. Tire rev's per mile of OEM vs your 'new' setup will dictate which tranny gear is best for any situation. Do the math as others have listed for each gear of your tranny vs the 'old' and 'new' diff ratio...then decide where you wish to be in any of those situations on engine rev's

Found this one but don't know if it applies to yours...PS...the onboard image function no longer seems to work with just a drag n drop...gotta have an url...

If me, I'd prefer to tow between 3.5K and 5K RPMs with this engine
Huntindog
Explorer
Nov 08, 2017
One thing to consider is that as you go to higher ratio ring and pinions is that it gets weaker the lower you go...The truck will feel a lot stronger, but will actually be weaker in the ring and pinion area... So The only real fix is a heavier duty axle that will be stronger with lower gears.
marcsbigfoot20b
Explorer
Nov 08, 2017
The first thing I would do to that suburban is call Black Bear and get a tune. With a good cold air intake and a tune you can gain ~20 hp/tq and have modified transmission shift strategies to keep you in gear and lockup longer. Add gears and it would do well....plus you may need a tune for the speedo anyhow if you do gears.

I was towing 7K tall trailer with a 99 Tahoe that I heavily modified (in my sig) and I just realized it could do it but it was working too hard for my driving style. Had to upgrade trucks....still have the Tahoe.