Bolt on turbo kit (51 Viewers)

[cary]

Would still love to see the dyno plot.

 

[junior80]

Gorgeous truck. Just ordered my suspension - 3" icon with DVS helper kit. Having a tough time deciding between 4.88s in the diffs and high range t-case gears for 35s.

I’ll be fitting the underdrive high range gears this week sometime. With 35s, I’ll either start a thread for a before after or find one of the ones already going to post a video or something

 

[haulin auss]

I’ll be fitting the underdrive high range gears this week sometime. With 35s, I’ll either start a thread for a before after or find one of the ones already going to post a video or something

I'm happy this conversation has come up. About to pull the engine for a rebuild before the turbo install and have been torn about what to do with the transmission and t-case while they're out. The truck already has 4.88s and 35s and sees just as much highway driving as trail riding.

For the t-case, I've been planning on rebuilding with CruiserOutfitters' Overhaul hit and while I'm in there, swapping the low range gear set and the high range set with the 10% overdrive set. I'm starting to second guess swapping the high range set given the noise reports and in general it being overkill with the 4.88s and turbo. My initial thought was that this should put my speedo right back to where it was from the factory (almost). Thoughts?

 

[HDJdreams]

I'm happy this conversation has come up. About to pull the engine for a rebuild before the turbo install and have been torn about what to do with the transmission and t-case while they're out. The truck already has 4.88s and 35s and sees just as much highway driving as trail riding.

For the t-case, I've been planning on rebuilding with CruiserOutfitters' Overhaul hit and while I'm in there, swapping the low range gear set and the high range set with the 10% overdrive set. I'm starting to second guess swapping the high range set given the noise reports and in general it being overkill with the 4.88s and turbo. My initial thought was that this should put my speedo right back to where it was from the factory (almost). Thoughts?

Transfercase gears don’t affect speedometer.

 

[haulin auss]

Transfercase gears don’t affect speedometer.

To dumb it down for a software developer like myself, wouldn't re-gearing the transfer case, just like re-gearing the thirds, affect the amount of rotations the wheels make per rotation of the transmission output shaft?

I know it's in no way directly affecting the speedo, but this setup should get my 35's closer to the distance-covered-per-output-shaft-rotation value (getting really technical there ) as stock gearing/tires, right?

 

[Bambusiero]

I'm happy this conversation has come up. About to pull the engine for a rebuild before the turbo install and have been torn about what to do with the transmission and t-case while they're out. The truck already has 4.88s and 35s and sees just as much highway driving as trail riding.

For the t-case, I've been planning on rebuilding with CruiserOutfitters' Overhaul hit and while I'm in there, swapping the low range gear set and the high range set with the 10% overdrive set. I'm starting to second guess swapping the high range set given the noise reports and in general it being overkill with the 4.88s and turbo. My initial thought was that this should put my speedo right back to where it was from the factory (almost). Thoughts?

315 (35"):
4.88 diff gears + 315 tires + 3.11 LowRange T-case + 9% OD HighRange T-case gears will put you at:
0.981 * stock RPMs in High Range. ( a mere 1.9% under revs, close to ideal)
3.254 * stock High Range in Low Range. (compared to stock 2.488 Low Range)
This gives you the best achievable Low Range / High Range ratio of 3.317.

37": (similarly)
5.29 diff gears + 37" tires + 3.11 LowRange T-case + 9% OD HighRange T-case gears will put you at:
1.002 * stock RPMs in High Range. ( a mere 0.2% over revs, practically perfect)
3.325 * stock High Range in Low Range. (compared to stock 2.488 Low Range)
Likewise, best achievable Low Range / High Range ratio of 3.317.
This combo on 35s would over-rev by 6.4% for high altitude and wintertime mountain chain mounting clearance - perfect.

Not sure what shows on the speedo though.

 

[bryson]

Transfercase gears don’t affect speedometer.

To dumb it down for a software developer like myself, wouldn't re-gearing the transfer case, just like re-gearing the thirds, affect the amount of rotations the wheels make per rotation of the transmission output shaft?

I know it's in no way directly affecting the speedo, but this setup should get my 35's closer to the distance-covered-per-output-shaft-rotation value (getting really technical there ) as stock gearing/tires, right?

The transfer case underdrive gears certainly change the overall effective gear ratio, just like re-gearing the axles. BUT, since the gear reduction takes place in the transfer case before the speedometer pickup (which is in the tailhousing of the transfer case) the speedometer readings are not affected by the ratio change like it would be with an axle ratio change. The relationship between engine RPM and indicated speed will be changed though.

In short, if your speedo is 5% off before t-case gears, it will still be 5% off after the t-case gears. But, you'll be at a higher engine RPM for the same speed.

 

[junior80]

The transfer case underdrive gears certainly change the overall effective gear ratio, just like re-gearing the axles. BUT, since the gear reduction takes place in the transfer case before the speedometer pickup (which is in the tailhousing of the transfer case) the speedometer readings are not affected by the ratio change like it would be with an axle ratio change. The relationship between engine RPM and indicated speed will be changed though.

In short, if your speedo is 5% off before t-case gears, it will still be 5% off after the t-case gears. But, you'll be at a higher engine RPM for the same speed.

That is annoying. I was under the impression that it would correct the speedo. However it’s still better for me to do the t case with the input and output seals and an output bearing. If I did diff ratios that would blow out to diff rebuild and new disks refurbed callipers and lockers because why do all that again later.

I’ll order a speedo correction box from marks and be done with it until I’m ready to do lockers, then put 1:4.88 in and fit 37’s too

 

[junior80]

315 (35"):
4.88 diff gears + 315 tires + 3.11 LowRange T-case + 9% OD HighRange T-case gears will put you at:
0.981 * stock RPMs in High Range. ( a mere 1.9% under revs, close to ideal)
3.254 * stock High Range in Low Range. (compared to stock 2.488 Low Range)
This gives you the best achievable Low Range / High Range ratio of 3.317.

37": (similarly)
5.29 diff gears + 37" tires + 3.11 LowRange T-case + 9% OD HighRange T-case gears will put you at:
1.002 * stock RPMs in High Range. ( a mere 0.2% over revs, practically perfect)
3.325 * stock High Range in Low Range. (compared to stock 2.488 Low Range)
Likewise, best achievable Low Range / High Range ratio of 3.317.
This combo on 35s would over-rev by 6.4% for high altitude and wintertime mountain chain mounting clearance - perfect.

Not sure what shows on the speedo though.

Just want to check you are calculating for a 9% Underdrive when you are writing 9% OD ?

 

[Bambusiero]

Under - over, the meaning can be confused, I suppose. It's relative.
The term Overdrive is used in the same sense as the vehicle's transmission is equipped with a button selectable Overdrive that reduces RPMs when engaged.
Then, Underdrive is the opposite, increasing RPMs.
This is from the following, published by CruiserOutfitters.

p.s. And adding a Turbocharger Overdrive increases RPMs in all cases (except in a whole different way, 'cause you can't help it)

p.p.s To put everything in the same terms:
Bigger tires is an Overdrive (reduces RPMs)
Higher ratio diffs is an Underdrive (increases RPMs).
An Underdrive compensates for an Overdrive, and vise versa.

 

[haulin auss]

I love this place

Thank you all for the clarification, makes perfect sense!

 

[junior80]

Under - over, the meaning can be confused, I suppose. It's relative.
The term Overdrive is used in the same sense as the vehicle's transmission is equipped with a button selectable Overdrive that reduces RPMs when engaged.
Then, Underdrive is the opposite, increasing RPMs.
This is from the following, published by CruiserOutfitters.

View attachment 1988661

p.s. And adding a Turbocharger Overdrive increases RPMs in all cases

Yeh i'm familiar with the od button. I was just referring to the optional 10% high range underdrive gears available. I'm putting a set in my t case to correct for the 35" tires. there is also a 10% overdrive for the high range in the t case available.

 

[Willy beamin]

My current gearing set up is:
37" km3s
3.1:1 low range gears
UD high range gears
4.88 in the diffs
part time kit
@ 80 mph the rpms sit @ 2700 - 2800
we will see what the turbo does to all this madness

 

[Bambusiero]

Guys, while there's obviously a relationship between available engine torque and gearing choices, it's really a cleanly separable relationship, as well.
To paraphrase the Bard - "To turbo, or not to turbo, that is the question."

The gearing subject came up, and there seemed to be some vagueness, so the above info & chart should clear it up.
I'll just point this out, and say no more - The T-case High Range and Low Range gears interact with each other. Not independent.
Look at the X= and Y= formulae in the chart.

However, this thread is about the Bolt on Turbocharger project , not about tire sizes, differential and transfer case gear ratios, so...
There are other threads for all that. Suggest dropping this .

 

[haulin auss]

Guys, while there's obviously a relationship between available engine torque and gearing choices, it's really a cleanly separable relationship, as well.
To paraphrase the Bard - "To turbo, or not to turbo, that is the question."

The gearing subject came up, and there seemed to be some vagueness, so the above info & chart should clear it up.
I'll just point this out, and say no more - The T-case High Range and Low Range gears interact with each other. Not independent.
Look at the X= and Y= formulae in the chart.

However, this thread is about the Bolt on Turbocharger project , not about tire sizes, differential and transfer case gear ratios, so...
There are other threads for all that. Suggest dropping this .

Oh, c’mon now, we’re just overly excited for our turbos

Next up, what color trucks are fastest with boost

 

[NLXTACY]

New truck is going to SEMA Garage tomorrow. Just need to remove the front driveshaft and bring two stock tires. They should have it done, UNMOLESTED, by Tuesday.

 

[LXDOC]

Now it is ready for drifting. Is a valet switch part of the kit?

 

[alia176]

New truck is going to SEMA Garage tomorrow. Just need to remove the front driveshaft and bring two stock tires. They should have it done, UNMOLESTED, by Tuesday.

Refresh our memories and for the newbies, what is SEMA's part in all this?

 

[NLXTACY]

Refresh our memories and for the newbies, what is SEMA's part in all this?

CARB certification






...and vehicle destruction

 

[Corbet]

Good to hear the SEMA schedule Joey.

As far as gearing it’s 4.88’s, 37’s, and the low range 3/1’s for me personally. I’m not willing to goto the tiny 5.29 pinions. I’d love the 100 series 5-speed Auto if a conversion kit becomes available.