2018 Tahoe-EXPERIENCE changing axle ratio?

[Danneman]

My research is turning up a lot opinions on 3.08 vs 3.42, and that has been helpful, but I can’t seem to find a lot of folks who have actually had the change done.

I have the 3.08 and per the manual my towing capacity goes from 6400 to 8400 if I had the 3.42.

I have the 5.3 engine and regular towing equipment, no max towing package. The boat I want + trailer + gas etc bumps right against the 6400 limit I have.

I do realize the front and rear diffs need the same ratio for my 4WD. And I presume the computer would need to be reprogrammed.

Anyone actually done this change? Any surprises?

 

[Danneman]

No one's made this change?

 

[swathdiver]

No one's made this change?

Lots of guys have done it with the older models and I'm not so sure that the GMT900s or K2s need to have any programming done as they have wheel speed sensors and sensors on the propeller shafts that determine rpms.

On the older trucks in certain instances, the payload capacity was not maximized unless one had the largest cooling system package offered as well. This was the K5L option and consisted of a larger radiator, 700 watt fans, engine oil cooler and an external transmission cooler. Does yours have those features?

The new T1 trucks have higher payload capacities because they gave them bigger radiators, fans, etc.

 

[Danneman]

I do have the engine oil and trans coolers, I saw those on the build sheet. Fan and radiator, not sure - do we know the RPO codes for those options?

My dealer just got back to me saying the speedometer would change and they have no way of recalibrating to the new ratio.

 

[fozzi58]

That's a load of BS. A simple hand tuner from Diablo, Evolution, or one of the many hand held computer tuners allow you to change that setting. Also you could reach out top BlackBear performance and speak with them about your needs. I am pretty sure they would be able to tell you if they could bump up the fan speed or change your shift points for betting towing. And I am positive they can reprogram your truck to match the gear ratio. If they can do it for tire and wheel combos, differential ratios is also just as easy.

 

[Danneman]

That's good to know, thanks for the suggestion.

 

[akbrener]

Find the axle assemblies, or pay to swap the ring and pinions all you should need is a tune. You could probably run it without the tune for a while as well, just may shift weird. Esentially you are doing the same thing as putting different sized tires on it, which is done all the time.

Not sure if the 6 speed trans would be good with 3.73s, but if you are going to just swap the ring and pinions you may as well upgrade a bit more. Could always add a little leveling kit and some 33's to help bring the actual ratio down a bit. my 08 with the 4 speed trans has 3.73s and its a greeat combo

 

[swathdiver]

I do have the engine oil and trans coolers, I saw those on the build sheet. Fan and radiator, not sure - do we know the RPO codes for those options?

My dealer just got back to me saying the speedometer would change and they have no way of recalibrating to the new ratio.

I do not know them for the K2s.

On the previous generation:

K5L - Enhanced Cooling Package (Description Changes based on Marketing and Years)
KC4 - Engine Oil Cooler
KNP - External Transmission Oil Cooler

 

[BMPNUGLS]

Not sure if the 6 speed trans would be good with 3.73s, but if you are going to just swap the ring and pinions you may as well upgrade a bit more. Could always add a little leveling kit and some 33's to help bring the actual ratio down a bit. my 08 with the 4 speed trans has 3.73s and its a great combo

If I were looking for the best towing ability I’d go with this recommendation! I’m also surprised that GM doesn’t offer 3:73’s in these SUVs (at least not nowadays)...I tried to find a XL Denali with 3:73’s when I bought mine. I came from a F150 Supercrew that had 3:73’s and there was a night and day difference in low end performance vs other F150’s I drove with 3:55’s or higher axel ratios! I’ve seriously considered switching out the Denali ring & pinions to 3:73’s as well.