Travco 270 lost the Hydrovac brake booster

[77Travco]

My 77 has hydroboost so most of what you guys have been talking about is foreign to me, lol. I will try to take a few pics tomorrow and post them up.

[RobC]

I will take a look today but yeah- pretty sure mine is hydroboost. I will grab some shots this afternoon and post them along with a few of my rig in its torn down state.\n\nRob

[Roadrash]

I'm looking forward to seeing some pics of the hydroboost setup.

[Acesneights]

My 77 has hydroboost so most of what you guys have been talking about is foreign to me, lol. I will try to take a few pics tomorrow and post them up.

\n\nhttp://dave78chieftain.zxq.net/HydroVac_brakes.html is a pretty good explanation of the Hydravac system.

[77Travco]

Sorry guys... I got completely side tracked this last weekend with other projects and forgot. I am at work today but will leave myself a reminder about this.

[77Travco]

It's pretty dirty under there with surface rust and all but here is a pic. Next time I drive by a car wash I need to power spray that area.\n\nPretty simple setup really... A Hydroboost unit attached to a master cylinder that then has the front and rear lines going through a proportioning valve (mounted on the frame) on their way to the wheels.

[Acesneights]

Way better setup IMHO.

[Dave78Chieftain]

To help people understand the RM400/M500 systems easier:\n\n1. When Dodge produced the original M500 chassis in 73/74 they designated it as RM400. Do not confuse that with the M400 chassis as in 73 that was RM350.\nIn 75 Dodge redefined all this making it retroactive to 73 (described in 1975 Dodge MH Supplement manual). RM350 was redesignated to M400 and the RM400 was redesignated to M500. Can really confuse you if unaware.\n\n2. Aftermarket parts places originally set up their data based on the original RM350/RM400 designation. Many of them did not change over to the 75 M400/M500 redesignation. So again, confusion. That is why I always say start with Dodge P/N for xref.\n\n3. Because a RV manufacture had to ORDER the chassis early from the chassis supplier (Dodge), they normally placed this years model (e.g 1976) on the previous years chassis (e.g. 1975).\n\n4. The original 73 thru 75 Dodge RM400 (M500) chassis ((http://dave78chieftain.com/M500_73-75-RM400.html)) was based on a Hydro-Vac Brake booster system (http://dave78chieftain.com/HydroVac_brakes.html). \nOriginally Dodge used the Bendix Twinplex system on the RM400 (M500) rear wheels (http://dave78chieftain.com/TwinplexBrakes.html). \nDodge started using to the Duo-Servo system on the RM400 (M500) rear wheels in 74/75 (http://dave78chieftain.com/BXDuoServoBrakes.html)\n\n5. In 76 Dodge converted to the Hydroboost brake system (http://dave78chieftain.com/hydroboost_brakes.html) on the M500 chassis(http://dave78chieftain.com/M500_76.html).\n\nWhen using my site, access to all of this information is from the hyperlinks at the top right corner where the configuration is described:\nM500 (RM400) 1973-75: http://dave78chieftain.com/M500_73-75-RM400.html\nM500 1976 and Later: http://dave78chieftain.com/M500_76.html\n\nAnd finally, when searching for chassis parts, do not search for the term Travco, always use the Dodge Chassis designation\nM300 or RM300\nRM350 or M400\nRM400 or M500\nM600\n\nDave

[77Travco]

Once again Dave, thanks for the info...\nSo my 1977 Travco motorhome probably has a 1976 M500 chassis under it? The reason I ask is because I am curious about my engines compression ratio as there seems to have been a change from 8.2:1 to 7.8:1 in 1977.

[Dave78Chieftain]

For reference:\nBoth the 73 - 75 and 76 - 77 MH Service manual says 8.12 to 1\n78 - 79 manual says 8.1 to 1\n\nDodge did start to de-tune the engine (carburetor mods and head redesign) to burn leaner in 75 in response to all the emissions tightening. I believe the 75 head redesign was what robbed most of the power.\n\nLocate your dodge VIN number to determine year (6th digit) 1976 = M50DA6S000001 http://www.classicwinnebagos.com/Pages_ ... .html#1974\n\nDave