peterk Report post Posted October 22, 2018 England Calling. 1990 Gulfstream 28ft on a Oshkosh Chassis, Cummins BT6 and Allison Transmission. Hi everybody, hope you guys are keeping well. Has anybody had any experience in installing a Exhaust Brake on a 1990 Allison Transmission, the free wheel overun type (sorry but I can't manage to read the model number on the Tranmission ID plate). We have uprated the engine output power a little (from 150hp to about 210hp) Brake system ( Discs all round)is working well but I'd be alot happier if we could install an Exhaust Brake. Look forward to your comments and suggestions Best regards Peter & Rayne Share this post Link to post Share on other sites
wolfe10 Report post Posted October 22, 2018 Peter, Best advice is to e-mail both Allison with your transmission model and serial number AND Cummins with your engine serial number to verify that you both can install an exhaust brake and then from Cummins the maximum backpressure the engine was designed to accommodate. It may be that you could fit one, but the exhaust springs would limit backpressure to where it would not be effective/not worth the money. Share this post Link to post Share on other sites
kaypsmith Report post Posted October 22, 2018 Peter, if the transmission is four speed Allison, most likely an HT740 in that model. Share this post Link to post Share on other sites
wolfe10 Report post Posted October 22, 2018 I suspect a much less "robust" Allison with a 150 HP 1990 rig. Might be an AT545. Share this post Link to post Share on other sites
dickandlois Report post Posted October 22, 2018 1 hour ago, wolfe10 said: I suspect a much less "robust" Allison with a 150 HP 1990 rig. Might be an AT545. Brett, this is some information I found on the AT545. Not sure it would be an ideal fit. The AT545 just freewheels! you can only control your speed with the brake. Rich. Share this post Link to post Share on other sites
wolfe10 Report post Posted October 22, 2018 Look forward to what Peter finds as he digs into this. Share this post Link to post Share on other sites
peterk Report post Posted October 23, 2018 Hi Guys I'll start digginf but I think Rich has hit it on the head as ours only Free wheels on over run. The good news is we've not spent any money yet, I take Wolfe's point it'll need heavier exhaust springs. I was hoping there was some addition valve block we could fit to convert the Trans into a locking type, so either I've got to find another Transmission or Torque converter. So that raises a key question is the actual Transmission dissengaging on overrun or is the actual the Toque converter dissengaging. ????? Cummins here in the Uk are not that helpful, so would anyone have any contact addresses in the US where I can track down some sense. As you guys were so helpful on the Front axle King Pin issues I owe you an update, the actual King Pins are great the problem is down the Shimm kit, there's too much play on the vertical plain on the Driver's side, it does not fail on the annual test but its something that needs to be sorted out, got absolutle no respeonse fron the Front Axle Manufacturerbut a friendly Truck repair shop help us nail the problem so shimms should be available when I know the Kng Pin diameter. Best regards to all Peter & Rayne Share this post Link to post Share on other sites
wolfe10 Report post Posted October 23, 2018 https://www.cummins.com/customer-assistance Be sure to include your engine serial number. Share this post Link to post Share on other sites
manholt Report post Posted October 23, 2018 The old and new Saga continues... Not easy to find American parts in Europe, so I feel their doing rather well. Share this post Link to post Share on other sites
obedb Report post Posted October 30, 2018 Entertaining, but you live in Great Britain. Why would you want to go to the expense of modifying something nearly impossible to do? Highest mountain pass ? Come on over hear, rent a unit with Diesel engine and an exhaust brake, and have the time of your life. You may do it only once because of the cost, but you will never forget it. Guarantee..😐 Share this post Link to post Share on other sites
manholt Report post Posted October 31, 2018 Byron. Your a day late and a buck short. They lived in Arizona from 1993 to 97. Seeing the USA is not the problem! They bought the unit from a farmer in UK...let's call it a Hobby! Works for me.😎 I have run into quite a few people from other countries, that do what you suggested and they love it. Some keep DP's in Storage here, and spend winter in them! Yes, FMCA members! Share this post Link to post Share on other sites
obedb Report post Posted October 31, 2018 More than a buck short, but we are comfortable.😉 Share this post Link to post Share on other sites
obedb Report post Posted November 1, 2018 OK! I get it now. He is from Great Britain, but lived in the US for a few years. The thing that I can not quite get past is that I navigated the Rocky Mountains in our 34' gas powered coach for many years. No exhaust brake or Jake brake was possible. Wolf Creek Pass, Monarch Pass, Million Dollar Highway (US 550) ,and the Slumgullion Slide ( unnerving even to me ) headed to Lake City Colorado. So now I live in in a flat environment, but I would still like an exhaust brake. I got it . Just kidding you Peter. Our British friend. 😊 Share this post Link to post Share on other sites
richard5933 Report post Posted November 1, 2018 10 hours ago, obedb said: ...The thing that I can not quite get past is that I navigated the Rocky Mountains in our 34' gas powered coach for many years. No exhaust brake or Jake brake was possible. Wolf Creek Pass, Monarch Pass, Million Dollar Highway (US 550) ,and the Slumgullion Slide ( unnerving even to me ) headed to Lake City Colorado. ...😊 Gasoline engines provide braking action by their nature just by keeping the transmission in gear and taking your foot off the throttle pedal. Not the same in a Diesel. Diesel engines on their own will provide very little braking action, which is why people add either an engine brake (Jacobs Brake is one brand), an exhaust brake, or a transmission retarder. Engine speed in a gasoline engine is controlled by a throttle plate which restrict air flow through the engine. In older vehicles the throttle plate was in the carburetor, in newer cars it's in the fuel injection system. Close the air supply into an engine and a manifold vacuum is created as the engine struggles to pull air against the closed throttle plate. This is what produces the majority of the braking action in a gasoline engine. A Diesel engine controls engine speed by modulating the fuel supply. There is no way to create an intake vacuum because there is no throttle plate. An engine brake (Jacobs Brake, Jake Brake) works by physically changing the way the cylinder valves work while the system is engaged. The engine is basically turned into a huge air compressor, and the noise heard when drivers engage the Jake Brake is the sudden exhausting of air from the cylinders as this process works. An exhaust brake works by creating a restriction in the exhaust system - similar to the way a gasoline engine creates braking action except on the other end of the system. Instead of restricting air flow into the engine, it restricts air flow out. Can't get air out and suddenly the engine is fighting against itself as it tries to push more air out the back end. Not all engines are built to handle the increased pressures created by an exhaust brake, which is why the OP asked his question. Retarders are devices used to slow a vehicle by adding friction or hydraulic pressure inside the transmission to work against forward motion of the vehicle. Various system are used by different manufacturers. Share this post Link to post Share on other sites
manholt Report post Posted November 1, 2018 Well written and informative to new and future motor home owners! Also of help to those who have a pull behind or 5'er! Share this post Link to post Share on other sites
dickandlois Report post Posted November 3, 2018 Richard ! You are correct regarding the newer drive trains. With the older coaches - things where not setup the same way. The automatic transmissions where free wheeling, lockup transmissions / torque where not on the market. Today the system will offer engine braking in the system except for first gear. Rich. Share this post Link to post Share on other sites
