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Cummins R2.8 Build

Before I adapted the Cummins to the T-5 , I would check to see what the cost would be to go from a T-5 to say an AX15 or NV3550. If the transmissions use the same adapter and there wouldn't much cost associated with swapping out the T-5 (as far as bolting to the engine is concerned), then I might would just use the T-5 and see how it goes. If there would be a big expense to swap transmissions after the engine swap vs before, then I would go ahead and swap to a stronger Transmission .

Looking forward to following the build!
 
A call to Novak might help with the Transmission decision, at least with what adapters are available. Sounds like you'll be more on road oriented for this build, so a 5 speed is the most likely candidate. As stated before, I'd avoid the temptation to run the T-5 .
 
jp360cj said:
Before I adapted the Cummins to the T-5 , I would check to see what the cost would be to go from a T-5 to say an AX15 or NV3550. If the transmissions use the same adapter and there wouldn't much cost associated with swapping out the T-5 (as far as bolting to the engine is concerned), then I might would just use the T-5 and see how it goes. If there would be a big expense to swap transmissions after the engine swap vs before, then I would go ahead and swap to a stronger Transmission .

Looking forward to following the build!
Click to expand...

I'm hearing this a lot, what are your thoughts about the 700r4 ? I'm thinking if I'm going to swap transmissions I'll go for an automatic and for my application I could use an Overdrive (4.10 gears)
 
gogop66 said:
I'm hearing this a lot, what are your thoughts about the 700r4 ?
Click to expand...
The 700R4 would be a good choice in an automatic, IMO. Or, as posted, the AX15/NV35xx. If you got a smokin' good deal on a NV4500, that would be bulletproof (and possible overkill).

My 2 cents, if you're going to be driving this daily, on urban streets, you should be thinking automatic. Every now and then I get a wild hair, and think I want a manual Transmission in my DD. After a couple of years, I invariably return to an automatic.
 
Big fan of automatics and the 700r4 is a great Transmission .

Geared right, you can do anything the manual guys do - with less hassle...
 
as stated stay away from the T-5 i have it in my 85 it is ok behind the stock AMC 258 i6 / 4.2l but it is not going to hold up behind the diesel i have a spare ax15 thats going into my cj when the T-5 gives up. as far as inter coolers are concerned to save money (same with the trany) go to your local junk yard and find a diesel truck and rob its inner cooler ur installer has to modify the grill to accept one anyway so save the money and go used same with the Transmission find a wrecked jeep and away u go. just avoid really hard hits roll overs are your best bet for good tranys
 
Manic Mechanic said:
as stated stay away from the T-5 i have it in my 85 it is ok behind the stock AMC 258 i6 / 4.2l but it is not going to hold up behind the diesel i have a spare ax15 thats going into my cj when the T-5 gives up. as far as inter coolers are concerned to save money (same with the trany) go to your local junk yard and find a diesel truck and rob its inner cooler ur installer has to modify the grill to accept one anyway so save the money and go used same with the Transmission find a wrecked jeep and away u go. just avoid really hard hits roll overs are your best bet for good tranys
Click to expand...

After talking with the shop that is going to help me with the install they are steering me clear of the 700r4, said it's too long and would cause problems with drive shaft angle, so it looks like perhaps an AX-15 mated to my Dana 300

Still working on which Change Air Cooler (CAC) to install, I'm thinking of getting one from a used BMW X5 or similar instead of buying the custom one from Axis Industries
 
gogop66 said:
After talking with the shop that is going to help me with the install they are steering me clear of the 700r4, said it's too long and would cause problems with drive shaft angle, so it looks like perhaps an AX-15 mated to my Dana 300



Still working on which Change Air Cooler (CAC) to install, I'm thinking of getting one from a used BMW X5 or similar instead of buying the custom one from Axis Industries
Click to expand...



I wondered about that but figured I’d shut up and let a pro decide.

Don’t forget too that the GM Turbo 400 came stock in QuadraTrac CJs, Cherokees, Wagoneers and trucks. It’s a 3/4 ton tranny in a 1/4 ton CJ. It’s an extremely rugged Transmission .


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007 said:
I wondered about that but figured I’d shut up and let a pro decide.

Don’t forget too that the GM Turbo 400 came stock in QuadraTrac CJs, Cherokees, Wagoneers and trucks. It’s a 3/4 ton tranny in a 1/4 ton CJ. It’s an extremely rugged Transmission .


Sent from my iPhone using Tapatalk
Click to expand...

Had a GM Turbo 400 in a 81 suburban and love that Transmission and never had any problems. Isn't the TH350 shorter?
 
Belizean said:
Had a GM Turbo 400 in a 81 suburban and love that Transmission and never had any problems. Isn't the TH350 shorter?
Click to expand...



It is yes. And Novak has adapters. Great tranny for a Jeep.

I’m an auto fan in case it wasn’t already obvious...


Sent from my iPhone using Tapatalk
 
Update:
Transmission : It looks like I will go with the AX-15, thanks for all of those that pointed me in that direction. I will mate it up to the Dana 300 , seems like the best route for my build.

Intercooler: This turned out a lot easier than I thought, lots of options for intercoolers, I'm going with a replacement style for BMW X5. The intercooler runs a couple hundred and then build some custom brackets for it.

Gearing: I need help in this area! My jeep came to me with 3.23's in it from factory. I put 4.10's in it a few years ago and they have been fine for my application. With the Cummins R2.8 however it makes power really low in RPMs and I would like to keep RPMs at or below 2000 RPMs most of the time for fuel economy and good performance. Running the gear ratio calculator (link below) it looks to me like my RPMs at 70 MPH will be around 2309 (4.10 gears, 33" tires, .79 fifth gear). I'm thinking of going back to the 3.23's which would put the RPMs around 1819RPMs at 70MPH which I think would be okay but.. thoughts? In my RAM 2500 my RPMs are 1470 at 70MPH and it gets around 22MPG.

I'm not really looking to get some ridiculous mileage I know this is a Jeep and low gears are good, Just looking for what is ideal for this engine. It should be noted that I drive about 6 hours to my wheeling/camping area so highway gears is useful.

https://cumminsengines.com/repower.aspx
 
I've still got the factory 2:73's in my 8 if you'd like to swap ;)
 
What is the weight of this diesel engine?
What else have you confirmed about getting this SMOG legal?
LG
 
Question for anyone following this thread:

I am buying the adapters from the R2.8 to the AX-15 and then the clocking ring to the Dana 300 . Advanced Adapters has recommended that I switch the clutch linkage to hydrualic vs mechanical while make the changes. Reason is to avoid possible binding. Thoughts?

Thanks!
 
The Cummings diesel puts out 385 ft. lbs. torque at 1800 rpm. So that would mean some twist in the engine mounting. The CJ clutch bell crank is connected to the frame from the engine so excessive twisting will pull it apart. I have seen guys use Jeep Wrangler hydraulic clutch linkage work well and a improved motor mount setup would help also. That what I would think.
 
What is that AX-15 tranny rated for in torque? With 2:73 R&P gears, that engine torque will all be put into the tranny.
LG
 
No idea on what the ax15 is rated for, but here are the specs for the engine, I don't think that 267 lb/ft tq is all that outrageous.


*267 lb/ft torque.

From Cummins website:

Displacement: 2.8 L (171 cu in)
Bore: 94 mm (3.70 in)
Cylinders: 4
Stroke: 100 mm (3.94 in)
Aspiration: Turbocharged & Aftercooled
Compression Ratio: 16.9:1
Torque: 267 lb-ft @1500-3000 RPM*
Fuel System: Bosch Electronic
Horsepower: 161 hp @ 3600*
Engine Weight: 503 lbs
Dimensions: 28.3 in (H) x 25 in (W) x 25.1 in (D)
 
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