5.38's/37's and a question

[BearDog]

Have been needing to regear for a long time for the 37's. Finally got it done last week. Took a 500+ mile round trip to do some wheeling. These are my thoughts...

The plan all along has been to go to 40's. After this trip, that plan has now changed. The 37's and 5.38's are an absolutely perfect combination. On highway in 8th and 70-80, the RPM's run 2400-2600...right in the V6 sweet spot. MPG avg (not that I care) is up 1.0-1.5 on the highway. Wheeling at Hidden Falls, the 5.38 did awesome with the 2.72 Sport t-case. Overall, it is my perfect setup. I may try a 38 tire, but the 40's are no longer on the table.

Question:

Truck now hits 8th almost religiously. The only time it doesn't is in two scenarios. One - when accelerating hard-ish up to hwy speed. It will shift normal all the way to 7th, then once at speed it will stay in 7th. I have to manually pick 8th. Two - cruising at hwy speed, it will downshift to pass or pull a particular tall grade. It will not go back into 8th. It just stays in 7th. In both scenarios, I have left it to change itself for several minutes, but it will not go back into 8th. Does it need a flash for the transmission so it can relearn everything? Other than those two issues, this thing is rock solid. It will even be in 8th at 35mph in town.

My opinion: 37's and 5.38's are absolutely perfect for my mission. I love this truck more and more every upgrade I do.

Sponsored

 

[ChiefsJT]

Thanks for the info. I’m currently on 37s and about to pull the trigger on gears and new tires. I was leaning towards 5.13s but your post has me thinking otherwise. Thanks!!

 

[BearDog]

Thanks for the info. I’m currently on 37s and about to pull the trigger on gears and new tires. I was leaning towards 5.13s but your post has me thinking otherwise. Thanks!!

Don't be scared. For me, it is the perfect combo.

 

[Levi.Butler]

Heck yeah, Johnnie! Glad to hear you enjoyed the trip and the gear/tire combo!

 

[BearDog]

Heck yeah, Johnnie! Glad to hear you enjoyed the trip and the gear/tire combo!

37's good...until I see your truck again and shove money to the bob tail

 

[Levi.Butler]

I know exactly how you feel! You saw the people I hang out with! My 39s seem so tiny compared to all of my friends! HAHA!

 

[Hasemano]

I’m about 1,000 miles into my 5.38 re-gear on a JTR after installing the MC 3.5” and fitting 37x12.5. I also have the 6-speed manual transmission rather than an 8-speed automatic. I agree, it’s simply perfect and an absolute joy to drive.

Unlike the stock configuration, where 6th gear felt more like “another gear,” it now seems to function more like a traditional overdrive.

Only negative that I can note from extensive 4HI use during a recent snowstorm is that the gears are now pretty loud when using 4WD, specifically when accelerating in 3-4th gear. That wasn’t the case when stock.

 

[BearDog]

No doubt. I think I'll look into the bed cut option first. Would still be good if I do the bob and use the bed as a trailer. I only came down on the rear side twice...and I knew it was coming so I made it easy. Both times were on the level 4 trails we did. This truck surprised the shit out of me with how capable it is off-road. I freakin' love this thing.

 

[Zachanadandy]

Some people love really deep gears. I read 8th gear at 35mph and think what a waste of 4 gears in the 8 speed. It’s a double overdrive transmission. There’s no reason to be in the 2nd overdrive at low speeds. Further, I agree 2800rpms is the sweet spot to start getting power out of the v6, but that’s not the point of the 2nd overdrive either. I’d rather see 2200rpm in 8th gear coming down a grade on the freeway personally. If I need 2800rpm the Trans will downshift just fine. I’m glad you’re happy with it, but I hated 5.38s with 38s. Even 4.56s with 35s felt too low at freeway speed with the 8spd.

 

[James H]

Did you use a Tazer or similar to let the computer know the drive ratio has changed?

 

[BearDog]

Of course ?

 

[AstroZombie]

nice, i am thinking of 4.88 for my rubi and 35's

 

[BearDog]

Pics like this have been posted before, but another set won't hurt. 5.38 Dana gears on 37x13.50 Ridge Grapplers at 30psi. Calibration needs a minor tweak. Truck reads exactly 1 mph slow compared to my aviation GPS.

 

[Planerdude]

Have been needing to regear for a long time for the 37's. Finally got it done last week. Took a 500+ mile round trip to do some wheeling. These are my thoughts...

The plan all along has been to go to 40's. After this trip, that plan has now changed. The 37's and 5.38's are an absolutely perfect combination. On highway in 8th and 70-80, the RPM's run 2400-2600...right in the V6 sweet spot. MPG avg (not that I care) is up 1.0-1.5 on the highway. Wheeling at Hidden Falls, the 5.38 did awesome with the 2.72 Sport t-case. Overall, it is my perfect setup. I may try a 38 tire, but the 40's are no longer on the table.

Question:

Truck now hits 8th almost religiously. The only time it doesn't is in two scenarios. One - when accelerating hard-ish up to hwy speed. It will shift normal all the way to 7th, then once at speed it will stay in 7th. I have to manually pick 8th. Two - cruising at hwy speed, it will downshift to pass or pull a particular tall grade. It will not go back into 8th. It just stays in 7th. In both scenarios, I have left it to change itself for several minutes, but it will not go back into 8th. Does it need a flash for the transmission so it can relearn everything? Other than those two issues, this thing is rock solid. It will even be in 8th at 35mph in town.

My opinion: 37's and 5.38's are absolutely perfect for my mission. I love this truck more and more every upgrade I do.

So what is your mileage?

 

[BearDog]

So what is your mileage?

I never pay attention to mpg because, frankly, I don't care. It's not why I bought my truck.

However, I knew guys here watch it like a hawk for some reason so I reset the counter for the first time since I bought it right after the gears were installed. No hard data yet, but it is trending up by about 1.0-1.5 mpg.

Sponsored