Skip to main content
Topic: U280 vs U300 (Read 2035 times) previous topic - next topic

U280 vs U300

Hello all,

I've narrowed down my search to either a U280 or a U300, but I have a couple questions.

1)  What year did these models switch to a wide body?  I think it was around 1992, but I'm not sure.  Did U280 and U300 both switch in the same year?

2)  For those of you with the U300 and the DD 8v71, have you had any issues finding shops that can work on them?  I've read in other forums that it's getting harder to find 2 stroke diesel mechanics, but I'm not sure if I should believe it.

Thanks,
Joe

Re: U280 vs U300

Reply #1
Joe,

The U300 DD is the 6V92.

Specs for various years: Foretravel brochures, specifications and manuals Information Links
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: U280 vs U300

Reply #2
Hey Joe, the U 280& the U 300 are about the same coach a few more things on the U300 depending on year, the wide body first year was 92 it was the 25 the anniversary of foretravel.
Others more wiser than me will add to this list of things, some say the 92 isn't as good as the later models it all depends on what you want and what's available to you.
IAM very happy with our 92 with no real problems. We have the 6/92 dedec with the 746 Allison's 4 speed. Good luck on you searching and ask away , lot of knowledge on the site.
Andy & Eileen
Riverton Wyoming
1992 U300  40' 6V92 TA
2007 Honda CRV
1998 Jeep Grand Cherokee) Build # 4135 Skp# 122921

Re: U280 vs U300

Reply #3
Hello all,

I've narrowed down my search to either a U280 or a U300, but I have a couple questions.
For those of you with the U300 and the DD 8v71, have you had any issues finding shops that can work on them?  I've read in other forums that it's getting harder to find 2 stroke diesel mechanics, but I'm not sure if I should believe it.

The 2-stroke Detroit engines haven't been produced in highway vehicles in nearly 25 years. Even when they were produced in highway vehicles they weren't nearly as common as were 4-stroke diesels. Therefore it only makes sense that it's getting more and more difficult to find mechanics who are familiar with them. That doesn't mean that they are bad engines--but it does mean that one needs to be aware of the challenges of owning one.
David and Carolyn Osborn
1995 U320C SE 40' Build 4726 Feb 1995
FMCA 147762
Motorcade 17186

Re: U280 vs U300

Reply #4
The Detroit Diesel 6V-92TA as found in U300 was the first electronic HD diesel made. Everything is done via the DDEC II (Detroit Diesel Electronic Controls) and has NO RACK to run regardless of what you might hear. It also is protected against low oil pressure, high coolant temperature, etc. It was the premium engine at that time. At 9 liters, it's the smallest of the 92 series with 12, 18 and 24 liter liter engines in the lineup. Mercedes/MTU now controls Detroit Diesel and still makes the engine for off road vehicles, generators, military, etc as there were 3.5 million of the 2-cycles made. Parts are available either from MTU or aftermarket suppliers like Mahle or Clevite. With a reasonably priced programmer/reader, the injectors may be tested, a fast idle used, etc. Pretty easy to learn.

Early U300s had the 300hp version and a 4 speed with the later 1992 models fitted with 350hp (just a software modification) and the HD garbage truck Allison 746 4 speed. The torque of the 350 was too high for the original Allison so the 746 was used as it became available. The horsepower is very detuned as fire trucks usually have 445hp and ladder trucks 500hp. In marine use, the hp is usually 535hp but can go up to 620hp maximum in the same engine. Naturally, TBO goes way down at this rating.

Later 1995 U300s didn't use the 6V-92TA as it would not pass smog so most were CAT equipped (the last year for CATs as they also would not pass smog) with some having a Cummins M11 engine. Big advantage here is the 6 speed transmission. This is a huge advantage coming off a stoplight/stopsign as the 6 speed has a 6.xx to 1 first gear compared to 4.xx to 1 in the four speed. The six speed also has a taller final drive so highway cruising is at a lower RPM and gives probably a half mpg advantage. 60-65 mph gives me about 10 mpg w/o toad, 8 or so mpg with toad in mixed topography. Fuel cutoff is 82 MPH (top speed).

Series-92: MTU Online

Advantages 92 Detroit vs Cummins:

92TA is 2-cycle is a military spec HD engine
Aftercooler is liquid cooled and under blower and turbo vs a remote mounted intercooler (CAC). Liquid cooled aftercooler is more efficient and less chance of cracking.
No external fuel injection lines. Each injector is a unit injector with integral pump.
Glass smooth at all RPMs
Lower EGT with 2 cycle so a valve failure is rare
No intake valves, 4 exhaust valves so even temps across cylinder head.
Well engineered exhaust manifold with much less chance of cracking compared to 8.3 Cummins.
Direct drive power steering pump.
Two camshafts with short pushrods so less chance of engine damage if max RPM exceeded on downgrades.
Very HD transmission cooler with less chance of failure and coolant ending up in the ATF. A potentially fatal and expensive mix.
Jake Brake on 350hp models. A HUGE advantage to me. 1995 U300 with the CAT also has a Jake Brake.
8.3 Cummins is not available with Jake Brake in Foretravels.

Disadvantages:
Most 92 series block heaters are installed in a very poor location and very inefficient. Almost mandatory is a remote mounted block heater if you want to start without a white cloud of smoke.
Since the 92 series is no longer installed in an RV, it is harder to get knowledgeable service unless you go to a Detroit Dealership.
Poor crankshaft pulley to hydraulic pump alignment done by Foretravel and should be aligned properly as it's easy to lose the belt and possibly damage the engine if the "override" is used. Easy to align pulleys.
Poor documentation as to belt part numbers, filters, etc in the manuals that came with the coach. Some information is incorrect.

Cummins advantages:
Current production for on road vehicles means easier service.
Heated air intake for better cold weather starting.
Up to 380hp in the latest RV installations from the 8.3 liter engine.
Later U280s came with 6 speed Allison World Transmission. An excellent RV automatic transmission for all around driving.
Waste gate turbo allows max boost at higher altitudes.

I've driven Detroits since the late 1960's in fire trucks and our personal bus conversion. Love them! Not to say that CATs and Cummins are not good engines. Many Cummins/CAT fans on our forum to tout their favorite's advantages.

Pierce

Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: U280 vs U300

Reply #5
have two 6V-92 in our 48' 1981 Westport tri cabin boat.

Cummins M11 in my U320

Really glad to have the 6V-92 in the boat, just so neat to hear, start immediately, one of my boat partners has learned how to work on them, and he is not a mechanic by trade, just mechanically inclined and smart (Alaska Airlines captain). really enjoy that boat with those powerplants

Love my Cummins too - actually would love to find a solid 6V-92 powered U-300 to restore at some point.
Tim Fiedler    2000  Foretravel U-320 4010
2000 Chevy Tracker 2 Door Convertible 4WD Now lifted 4.5"
1985 Citroen 2CV6 Charleston
Murphy Rebel on wheels with 175HP Titan
Cessna 185 on Aerocet 3500 straight floats. (1/4 share)
1980 48' Westport MY (!/4 Share)

Re: U280 vs U300

Reply #6
I have a 1994 U300, with the Detroit 6V92  350 HP, 4 speed allison transmission.  No Problems with the set-up or maintaining my unit. You must Follow Lubrication Specifications on engine oil, Straight 40 or 50 weight, Delo or Shell T1. The only thing I do different then most is about every third fuel fill up I add 1 or 2 quarts of two cycle oil too the fuel tank to help lubricate the system, I do this because the new diesel fuel blend has less oil content.
The selected media item is not currently available.
Gerry & Brenda
CHARLOTTE HARBOR, FL
1994 Grand Villa - # 4466
U300 Unihome - 6V92 Detroit
4 speed Allison - Jake Brake


Re: U280 vs U300

Reply #8
yup

still love them...

Tim Fiedler

Sure Start Soft Start - home of SureStart soft starters TCER Direct - home of Generac Approved Aluminum and Copper TCER Composite cable generator-gas-prod - home of X-Riser Gas Risers for PE installation Call me at 630 240-9139
Gen-Pro
Tim Fiedler    2000  Foretravel U-320 4010
2000 Chevy Tracker 2 Door Convertible 4WD Now lifted 4.5"
1985 Citroen 2CV6 Charleston
Murphy Rebel on wheels with 175HP Titan
Cessna 185 on Aerocet 3500 straight floats. (1/4 share)
1980 48' Westport MY (!/4 Share)

Re: U280 vs U300

Reply #9
Tim,

Nothing wrong with the old school mechanical Detroits. They require zero electrical hookups aside from the starter motor. The lift pump is mechanical so once running, they stay running. I never liked the fuel valve that requires 12 or 24 volts to stay open. VW diesels are like that. Mercedes uses a vacuum actuated valve to shut down with an emergency mechanical link as a back up.

In starting mechanical Detroit that has been sitting for years, you should make sure the rack/throttle is not sticking as the engine could immediately go to high RPM. If an injector is stuck, it's pretty easy to free it/them up. See YouTube for DIY videos for freeing the rack as well as freeing an injector in place.

The mechanical Detroits also have very inexpensive unit injectors in comparison to the high priced electronic injectors. The last mechanical unit injector I replaced was only $50 so the cost to replace all eight in my 8V-71 was about the same as one electronic injector.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: U280 vs U300

Reply #10
Boat has been used about 250-300 hours a year last 12 years. Basic maintenance. No smoke, great sound. About 10GPH total at 10 knots

Tim Fiedler
Gen-Pro.biz
630 240-9139
Tim Fiedler    2000  Foretravel U-320 4010
2000 Chevy Tracker 2 Door Convertible 4WD Now lifted 4.5"
1985 Citroen 2CV6 Charleston
Murphy Rebel on wheels with 175HP Titan
Cessna 185 on Aerocet 3500 straight floats. (1/4 share)
1980 48' Westport MY (!/4 Share)

Re: U280 vs U300

Reply #11
Joe, reason we went with the U300 over the U280 was towing ability. The U300 can tow 6000 pounds, while the U280 is limited to 2000. That really limits your towed.

As has been mentioned, finding techs to work on the two cycle Detroits is becoming more of a challenge as the people who know them are retiring and the younger ones don't know them. I suspect that there will be at least one or two techs in the Nac area who know these engines.

Re: U280 vs U300

Reply #12
Can't see a real reason for the difference in towing capacity. The frame and brakes are the same. The only thing I can think of is the Jake vs retarder. If I owned a U280, I don't think I would worry too much about it. I watched a U300/280 tow a long construction trailer with a Case 580 plus other construction equipment on it. The trailer must have weighted a couple times what the coach did and on flat ground, they were going at least the speed limit.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: U280 vs U300

Reply #13
I would guess that once you eleminate the valve train components any normal diesel mechanic should be capable of maintenance or repair. Just make sure you get the correct DD 2 stroke motor oil, better yet have the correct oil onboard for a full change.
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: U280 vs U300

Reply #14
Yeah, sure!! The diesel engine shops today don't want anything to do with any diesel engine not equipped with an on-board computer that will do the diagnostics for the "mechanics".
Been there, tried that!!
Dropped our coach off at one of the top shops in the area. Got home and had a message from them saying to come and pick up our coach. No one there wanted to or could work on our coach without throwing a lot of parts at it to try and find out what was causing my problem. No power/fuel to the engine after 3-5 minutes running (DD 8.2L turbo-charged V8)
Found a shop up in the next county. The guy drove it down the road, turned it around, experienced my problem, pulled the coach into the shop and put a pressure gauge on the fuel supply line. Then proceeded to take off the pressure valve, blow out the line and then reassemble with a new pressure valve. Fired right up and now runs great!!
Nitehawk,  Demolition Lady, & our NEW master, Zippy the speeding BB cat.
1989 Grand Villa 36' ORED
Oshkosh chassis, 8.2 DD V8
2006 Saturn Vue AWD

Re: U280 vs U300

Reply #15
GCWR for the U280 as of 7/1/95 was 36,000 lbs.  ours comes in at about 27,000 before the Jeep.  That leaves me with what should be plenty of room ( 9,000 lbs ) to tow.      Sure not going up a 6% grade faster than 45 mph towing 9 grand though.
Robert and Susan Moe Sr.
 1995 36' 280 WTBI 8.3 3060r
 1200 watts on the roof, 720 Ah of lithium's
 Build # 4637. Motorcade # 17599
        FMCA  # 451505
        18  Wrangler JLUR
         

Re: U280 vs U300

Reply #16
GCWR for the U280 as of 7/1/95 was 36,000 lbs.  ours comes in at about 27,000 before the Jeep.  That leaves me with what should be plenty of room ( 9,000 lbs ) to tow.      Sure not going up a 6% grade faster than 45 mph towing 9 grand though.
The GVWR is 30,000 lbs the GCWR is allowing for a 6,000 lb towing capacity.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: U280 vs U300

Reply #17
Oh,,  I was thinking that if a person ( me) had the GV under the max (28,000)) then it left more room ( weight ) for the GC ( towing).  Wrong ??      6,000 is still plenty though.
Robert and Susan Moe Sr.
 1995 36' 280 WTBI 8.3 3060r
 1200 watts on the roof, 720 Ah of lithium's
 Build # 4637. Motorcade # 17599
        FMCA  # 451505
        18  Wrangler JLUR
         

Re: U280 vs U300

Reply #18
You have the right idea. The GCWR minus the GVWR shows how much you can tow--as long as you don't exceed the hitch capacity. I'm not sure of the stated hitch capacity for either model.
David and Carolyn Osborn
1995 U320C SE 40' Build 4726 Feb 1995
FMCA 147762
Motorcade 17186

Re: U280 vs U300

Reply #19
As far as finding someone to fix your engine There is always someone that knows someone that knows the guy that knows about those engines. The good news is if you do good maintenance keep good hoses and belts on them they are so reliable that breaking down from a engine related issue should not be a concern. These engines are in many many sport fishing boats for a reason Reliability! Don't worry about the engine as much as all the other thing's that can strand you...
91 GV U300 Unihome 40' Build 3811
6V92TA Detroit

Re: U280 vs U300

Reply #20
My problem was NOT an engine related problem. It was a fuel supply problem that had apparently built up over time, compounded by age of the coach, and yet, after calling around and going around to almost every single diesel shop in the northern half of Wisconsin I finally got a lead on someone that was familiar with and did repairs on the old DD engines/those without computer controls.
The man was familiar with these DD engines up here because they are used in school buses, fire trucks, and stationary irrigation systems.
If there was a computer diagnostics system on board then the problem would most likely have been called up and repaired without a lot of part swapping and head scratching guesswork.
Nitehawk,  Demolition Lady, & our NEW master, Zippy the speeding BB cat.
1989 Grand Villa 36' ORED
Oshkosh chassis, 8.2 DD V8
2006 Saturn Vue AWD

Re: U280 vs U300

Reply #21
For between $100 and $200, several members have been able to pick up a Pro-Link 9000, a diagnostic testing tool for our 92 series. I keep one in the coach and another in the garage. All the 2-cycles installed in Foretravels are electronic engines. Almost 50 readings and settings are available with the tool. While some items can have their settings changed, the horsepower cannot be upgraded. A Detroit dealer has to do that and 350hp is the EPA max unless you have a fire truck or marine engine serial number to use.

The 6V-92TA installation was not thought out that well for our coaches with a terrible air intake location (along with the Cummins air intake in the U280). This was finally fixed in the mid 1993 models with the intake move from the ground to about 3 feet up on the side of the coach.  My ex-Greyhound had a military type installation with zero belts. Everything was gear driven including the radiator fan, the AC PTO and the 300 amp sealed oil cooled brushless alternator. No overheating problems, no loosing belts, etc.

Until 1995, the engine access in both U300/U280 was poor. Even then, engine removal is still difficult. The rear bumper and frame cross members could have been made removable so the engine could slide straight out easily.. This is a big reason our coaches cost so much to work on. With modular connections, any of our engines could be removed in an hour or so. If GM could do it back in the 1950's, we could today.

Pierce



Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: U280 vs U300

Reply #22
Wow, thanks everybody for the input!  I learned a bunch.  It seems like either model would work for me and I should probably just look more at condition of the coach. 

That said, anybody know of any good U280s or U300s for sale?  I'd be looking for a 36' and probably wide-body (so, 92 or later), but I wouldn't rule out something pre-1992 either.  I checked the classifieds section, but didn't see anything there that was a match.

Thanks again,
Joe

Re: U280 vs U300

Reply #23
When we were looking for our coach (took a year!), we found it on: www.rvtrader.com
1993 U-240 "La Villa Grande"..CAT 3116 w/ Pacbrake PRXB...Allison 3060 6-speed..
Previous: 1983 Airstream 310 turbo diesel, 1979 Airstream 280 turbo diesel
                                      Build # 4297
                                      PNW natives
                      Home base:  'Cactus Hug' (Ajo, Arizona)
                        DW Judy & Chet the wonder dog
                        Full-Timers 'Sailing the asphalt sea'

Re: U280 vs U300

Reply #24
Took us a year plus also but we found EXACTLY what we wanted on this forum.
The important stuff for us was length (36), bathroom layout (walk through),engine size/access ( 8.3,side radiator) and color (DW).....  hopefully it's the "last coach first " thing. 

          Big thanks to Bob Hall for passing on a well maintained coach.
Robert and Susan Moe Sr.
 1995 36' 280 WTBI 8.3 3060r
 1200 watts on the roof, 720 Ah of lithium's
 Build # 4637. Motorcade # 17599
        FMCA  # 451505
        18  Wrangler JLUR