Duramax 6.6L FJ80 ratios and size

[TwoTonic]

We're just starting to do planning on putting a Duramax diesel into a 1992 FJ80.
To work well with the diesel's powerband, we need taller gears than the stock-- need to at least go with 3.73s like in the FJ60s... Does anyone know of gearsets/suppliers for the FJ80 differentials that could take us down to 3.73, or better still, 3.42? Most guys are going shorter, even up to 4.88s, but we need to go the other way. Any easy way to go taller, instead?

Size of engine has been a big concern-- initial measurements show the DMax to be shorter than the 3FE and not as tall as the Atlas we did recently. Top of intake to bottom of pan is actually about 2.5" less on the DMax than the I-5... so we have a good shot.

Width is the largest question, especially clearance with the steering linkage. The pan is also quite wide so we'll have to finesse clearance around the front diff, too.

We'll post pics as we go.

 

[Gordopescado]

Thats a dream of mine.

 

[jeepocabra]

You could go up to 33" or 35" tires with the stock gears. That would probably get you to about the right range. On our work truck with 4.10's and 33 the diesel is in about the right range.

What transmission are you going to use? Surely not the A440f?

A lift will also help you on the front diff clearances.

 

[ThePookieBear]

You kids are crazy!! A good crazy of course.

 

[matt49]

cant wait

 

[Tapage]

Good swap .. I love to see it ...

There is no ( at least I don't know ) of 3.** gears for the front 8" HP 3rd member .. so as others said, simple solution it's upgrading your tire size ..

 

[retrofive]

Good swap .. I love to see it ...

There is no ( at least I don't know ) of 3.** gears for the front 8" HP 3rd member .. so as others said, simple solution it's upgrading your tire size ..

After all 39's are new 37's.

 

[Tapage]

After all 39's are new 37's.

damn .. need to comment it to my wife ..

 

[locrwln1]

Like others have said, I think your only choice is for the rubber overdrive (bigger tires). I don't know of any 3.** ratios for the front third member.

As always, take lots of pictures. Can't wait to see the progress and results.

Jack

 

[TwoTonic]

ZF Transmission with Duramax

You could go up to 33" or 35" tires with the stock gears. That would probably get you to about the right range. On our work truck with 4.10's and 33 the diesel is in about the right range.

What transmission are you going to use? Surely not the A440f?

A lift will also help you on the front diff clearances.

We've been running the numbers on tire sizes and are planning to go to at least 33's. We'll be converting to manual, so we can use the ZF 6-speed with it, too.

 

[91Cruizer]

I wish I had your problem. A Duramax would be very nice.

 

[Lka1988]

Size of engine has been a big concern-- initial measurements show the DMax to be shorter than the 3FE and not as tall as the Atlas we did recently. Top of intake to bottom of pan is actually about 2.5" less on the DMax than the I-5... so we have a good shot.

I've had the opportunity to see a few different diesel V8s on engine stands. I'm fairly surprised by how (relatively) small the Duramax is compared to the old GM 6.2L, a Cummins 5.9L (not a V8, I know), or even a regular 350.

Want to see more....

 

[TwoTonic]

I've had the opportunity to see a few different diesel V8s on engine stands. I'm fairly surprised by how (relatively) small the Duramax is compared to the old GM 6.2L, a Cummins 5.9L (not a V8, I know), or even a regular 350.

Want to see more....

I've got the Duramax in the shop next to a fully-dressed L92 and they are basically the same size. DMax does have a very large pan, but that's about it. If a SBC will fit we think the DMax will, too.

The bummer is that with all GM's financial problems, they've suspended work on the "baby" Duramax-- It must have been close to done, as it had been planned for release in light trucks in 2010. It was (and may still someday be) even more compact than the LQ4/9 gasoline engines, and would have fit in a lot of potential conversion targets, like FJ40s and 60s.

They apparently did innovative stuff like put the exhaust manifolds INSIDE the V and integrated the whole thing directly with the turbo assembly. This is a very compelling configuration for thermodynamic efficiency and compact packaging. Was rumored to be about 300HP and 475TQ in a very small package.

May never make it to market.

 

[Atoyot1031]

You could go up to 33" or 35" tires with the stock gears.

A lift will also help you on the front diff clearances.

I think there's a reason Proffitt's requires at least a 4" lift and 35s their deisel conversions (They use the 4bt though, IIRC).

Search under GreaseCruiser's name, and you'll find lots of deisel info not just on 80s.

 

[Tapage]

We've been running the numbers on tire sizes and are planning to go to at least 33's. We'll be converting to manual, so we can use the ZF 6-speed with it, too.

which it's the large OD on the 6 speed ZF ( and 5 speed if you have the numbers . ? ) just to compare to with mine ..

I thought ( and love how it looks ) the 315 on 80 series .. with Duramax power and 6 speed ZF sound like a great combo to me ..

 

[TwoTonic]

which it's the large OD on the 6 speed ZF ( and 5 speed if you have the numbers . ? ) just to compare to with mine ..

I thought ( and love how it looks ) the 315 on 80 series .. with Duramax power and 6 speed ZF sound like a great combo to me ..

ZF 6-speed has a 0.50 overdrive, which helps the issue. It's quite a gearbox. We're still thinking we'll go to at least 33s.

 

[Atoyot1031]

Don't you guys know? 37s are the new 33s.

https://forum.ih8mud.com/80-series-tech/279947-just-another-80-trxus-37s.html

 

[ThePookieBear]

What about swapping the thirds from the other diesel cruisers that the 3.** gears? I thought I read somewhere you could. Maybe I'm just dumb though...

 

[TwoTonic]

What about swapping the thirds from the other diesel cruisers that the 3.** gears? I thought I read somewhere you could. Maybe I'm just dumb though...

Thanks! I wonder what configuration was for diesels sold in Australia and ROW during those years. That would be an elegant solution. We haven't been able to find taller gearsets in the US, so will do some research.

 

[Tapage]

ZF 6-speed has a 0.50 overdrive, which helps the issue. It's quite a gearbox. We're still thinking we'll go to at least 33s.

wou .. ! that's OD .. !

and the 5ft it's . ?