Engine and transmission swap

[Cary and Don]

If we swap out a 8V71 and Alllison 740 for a 8V92 and an Allison HTB748 with retarder.

What will the difference in length be?

Don

[TomC]

The 8V-92TA has a longer crank out the front to facilitate the big vibration dampner. Otherwise, the dimensions should be the same. You'll just have to get maximum cooling-the 8V-92TA is one of the hardest engines to keep cool. Good Luck, TomC

[HB of CJ]

Did the HT 740 family have two, (2) different types of transmission retarders?  Was one inside the convertor assembly and the other a heavier unit that actually added about 3-6 inches to the length of the tranny?  Some help here please ... it has been too long.

Also consider, FWIW, all that retarder heat must go somewhere.  Usually it is dumped into the transmission cooler, or sometimes just a loop through the water radiator.  Tranny retarders seem to work great for brief periods of time.  Long term use?  Heating?

Dunno.  A Jake Brake dumps about 70% of the energy absorbed as heat back into the water radiator.  The remaining 30% gets dumped to the outside world as heat ... and a cool noise.  A Tulsa type drive shaft retarder works super great.  HB of CJ (old coot)

That heat is dumped into a heating coil grid like a train locomotive with dynamic braking?

[luvrbus]

The retarder on the 748 will make the setup 5-1/2 in longer then add 2- 1/2 inches for the 8v92 do away with the miter box and go to a 90 angle drive at the pillar block at the radiator that engine probably has a gear driven alternator or you can belt drive it off the front or rear
If it's going in your Eagle you will need a front mount for the turbo and air horn or raise the bed it's not that hard to do except for the rear electrical panel and it may take some more modification to the drivers side frame also, they have several different rear covers for those that will change the length 

good luck

[wg4t50]

My MH4000R would be about 5-6" longer too for the hydraulic retarder, does require a larger heat exchanger on lower radiator hose, am using the ISM500 Cummins.
Would not own a coach without the retarder, after the MC7, the difference is way more than massive with the disk brakes added, stops like a car so must have everything secured or if you have to get on the brakes hard, the junk all comes forward big time, pots, pans, chairs, people, computers, you name it as it piles up in the front.
This retarder adds 2,000 fl lb torque resistance to the driveshaft, that is noticeable.
Dave M

[pvcces]

HB of CJ, can you tell me how you found the figures for the Jacobs Brake? I was under the impression that a much larger percentage of the energy went out the exhaust.

Thanks.

Tom Caffrey

[TomC]

Jake brakes work so well, Cummins on their ISX-15 and Detroit's DD13, 15, 16 have the Jakes built into the engines.
Hydraulic retarders work really well around town with trash trucks and transit buses. But on the road, hydraulic retarders have to be dumped numerous times to keep them cool when coming down a long grade.
Jake brakes will keep the engine warm when coming down a long grade, so when you get back on it at the bottom, the engine is still warm-minimizing smoke. Good Luck, TomC