Mating a Cat to the Allison HT755

[waterlodge]

I misspoke it's only 3" longer. According to the Allison specs , the 4000 series without PTO is 30.54" long and with PTO it is 33.41"
The HT755 is listed at 43" , I think that's the 10" difference that was in my brain somehow.

[sledhead]

Waterlodge I sent you a P M

dave

[6805eagleguy]

Is your engine a 3406e?

[waterlodge]

I called up several Allison dealers. One of the Dartco engineers I spoke to was extremely helpful. He found that all the parts to mate my engine and transmission were readily available from them new. Or at least they seem to be -- I need to send them some measurements to make sure their computer came up with the right stuff.

They also convinced me to upgrade the transmission as well. They can sell me a 4560 transmission with new computer, wiring harness, mechanical TPS, flexplate, all ready to plug and play. It's pricey but it will be a good upgrade from the HT755. I must say the 755 has served me well, never had issues. It's just getting old and the 4500's have higher HP ratings, lower starting gear, overdrive, all good things to have.

I was originally going with a 3408 cat but I couldn't help myself and bought a 3412. It's badass. It needs to be completely rebuilt so before buying expensive Allison stuff I first need to go over this engine and make sure there aren't any showstoppers, like the broken crankshaft that the Cat engines 3408 and 3412 can suffer from.

[luvrbus]

LOL you are joking ,with the 3412 you would need another axle to carry the the 3412

[waterlodge]

It does, it has a tag axle

[luvrbus]

It does, it has a tag axle

You will need another one ,I service one at the mine the friggn radiator is 7 ft x 5 ft by 8 inches thick

[waterlodge]

Meh, I calculated it will increase the overall weight of the RV by about 7%.

[luvrbus]

Go for it

[waterlodge]

I have an 8V92 sitting here , ready to be installed.
Then I was watching Bus Grease Monkey to inframes on one after the other 8V92
Then I remembered how I've already had several 8V92's go south on me as well.
Then I remembered how I could barely get in and out of campgrounds in Colorado.
The 3408 has a lot more torque than the 8V92 so that's what I was thinking of when starting this thread.
It ended up that the one I was looking at was a PC engine. The 3408 PC's are kind of lame.
Found a 3412 DI
It was cheap because it's in unknown condition , so I'll be going through it before even pulling the old engine out. The achilles heel of these engines seem to be broken crankshafts so that'll be first on the checklist.
Do you know of any cheap parts sources?

[luvrbus]

The 3408 is 18L engine sure it has more torque than a 13L 8v92 ,I had the 3408 in 3  CAT scrapers only problem I ever had was they cracked heads or break head bolts never broke a crank in one  They were good engines just that they were thirsty for fuel like 200 gals a day.The 3412 is a monster of a engine and a heavy sucker

[chessie4905]

Wouldn't be simpler to set up a V12-92?

[luvrbus]

Wouldn't be simpler to set up a V12-92?

Hope he takes photos stuffing a 27L (1650CI) 3412 engine in a Blue Bird

[azdieselman]

WAIT!!!!!

You want to some how fit a 3412 in a BB, AND find "cheap" parts?

If the place you got the engine from GAVE you 20K to haul it off, You're still WAY upside down.

BTW, I'm all for creativity, But I prefer to stay reasonable.
I'm sure the frame, suspension and axles will handle that without any issue.

I hope it goes as planned for you.

[luvrbus]

He should have plenty of power the 3412 is the C-27 used in the D-10 dozers that weighs 155,000 lbs