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91 u300 transmission retarder

 Considering buying a 91 u300 SAi and selling my coach.  Seller who is experienced in motorcoaches swears it has a transmission retarder, and even my 89 Allison MT-647 tranny could be bought with a retarder. Beamalarm 91 u300 specs indeed show the transmission retarder as standard. In 92 specs they show a Jake brake. Does anybody have a 91 u300 with a retarder, and or know if they were problematic? Rear radiator 6v92 coach so don't know how much hp either.
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: 91 u300 transmission retarder

Reply #1 –
The 91 would have a switch on the lower dash bottom left labeled retarder. No manual lever.  No 700 series trans until the much preferred 93 350hp wide bodies.

Your 89,300 cat pulls the hills better than the 300hp/820 torque 6v.  Especially over 5k altitude. 

Time it from zero to 60.  Your 89 does it in less than 30 seconds. 

The 350 93 will bring a grin to your face plus a side drive radiator you already have in the ORED.

Although Kansas does not have hills to speak of.
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: 91 u300 transmission retarder

Reply #2 –
Retarder on '91, Jake on '92 and later. Jake coaches have the same switch labeled "retarder" on the panel. Foretravel never had the letters changed or I have not seen one. '91 has 300hp and  4 speed 647 Allison vs 4 speed 746 in the later 350hp the next year. 300hp Detroits had "Detroit" in big embossed letters on shorter valve covers. This indicates no Jake. Both lock up at the middle of second gear, all of 3rd and 4th. Horsepower and torque rating is programmed by the ECU (DDEC II). Same engine as 500hp FD ladder truck or 620hp marine application, just different programming.

Advantages: 96 inch 300hp U300 is probably as fast as the later 350 hp as the coach is a little lighter and the hydraulic fan system sucks up lots of HP on the side radiator (probably 60 hp on the 1993). Both U300s (and U280s) have the terrible engine air intake behind the rear wheels. Changed sometime in 1993 to well above the rear dock light. '92 had the vertical radiator with one fan, '93 had the horizontal radiator with two fans. Both are marginal for cooling. Rear radiator makes engine access harder but much more simple and less maintenance (after the fan blade is changed).

Don't know about the 300hp but our 350hp at 5000 feet is as fast as a U320 M11 36' on hills if the ratio matches the grade, Otherwise, the 6 speed Allison is a big advantage off the stop sign, on many hills and drops the RPM at cruising speeds.

Figure 10 mpg in mixed topo w/o toad and no headwind. 8 mpg with toad and less in all mountains and or headwind.

Jake is a nice advantage if given a choice. Detroits don't have waste gate turbos, all have aftercoolers (no intercoolers/CAC).

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

Re: 91 u300 transmission retarder

Reply #3 –
I have a '91 U300 SAI, 40 footer.
Yes, retarder is standard.  There is no joystick, just a switch on the dash and when ON the retarder is applied with the brakes.
Here' an old post on how I use it : Detroit/Allison Confusion
No issues at all in terms of reliability.
Engine is 300 hp and that's pretty much at the limit of the transmission input torque, so don't expect to bump up the HP.

Significant differences between a '91 and '92 (respectively):
96" wide body vs. 102" wide body
300 vs. 350 horsepower
rear radiator with conventional belt driven fan  vs. side radiator with hydraulic fan
600 series transmission with retarder verses 700 series with a Jake Brake on the engine
Manual air leveling vs. HWH computer controlled air leveling.

The rear radiator makes working on engine harder (access from ground or above from bed) but there's no hydraulic fan system to worry about and the whole power train system has been very reliable.  The only thing hydraulic on the whole coach is the power steering. 
The manual air leveling is beautifully simple and easy to use with no electronics.  Another post: Travel mode leveling

SAI is a nice floorplan.  Access to the back of the frig is through the closet in the bathroom.  A little strange and inconvenient, but the components back there are better protected from the elements.  There's a vertical tunnel from the basement floor to the roof to provide ventilation - it does eat some storage space.  Also, the front AC will not flow to the bedroom due to the offset hallway.
John Fitzgerald
1991 U300 (SAI) Side Aisle Island Bed 40'
Detroit 6V92 with Allison Retarder
Meridian (Boise), Idaho

Re: 91 u300 transmission retarder

Reply #4 –
John F make a good point about the manual air leveling. Given the choice, I would much prefer the manual leveling. 102" is nice and is noticeable but 96" works well too.

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

Re: 91 u300 transmission retarder

Reply #5 –
ON our 91 GV with the 3208TA, there is a retarder in the exhaust that is operated by a foot sw. on the floor by the left foot.  Is this a standard kind of retarder or is it after market?  ----  Thanks and have a great day  ----  Fritz
Fritz & Kathy Johnson
1991 36'

Re: 91 u300 transmission retarder

Reply #6 –
The 647mtb locks up in mid third. 

The 350/1050 torque is considerably faster than the 300/820

We raced them side by side several times.

The 1988's u300 were 277/840.  At least a coach and a half  length faster to 60 mph in a side by side.

If I owned a pre 93 300hp 6v it would be reset to 277/840. 

I had Detroit change them for marketing purposes to the 300 at the unihome introductionary meeting in Oct 87 at Nac.

"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: 91 u300 transmission retarder

Reply #7 –
Quote
there is a retarder in the exhaust that is operated by a foot sw. on the floor by the left foot.  Is this a standard kind of retarder or is it after market? 

Fritz, that sounds like a foot operated PAC brake. I drove a 92 one time that had one.
jor
93 225
95 300
97 270
99 320

Re: 91 u300 transmission retarder

Reply #8 –
All things considered, I think I will keep my current coach. I think my galley has more storage and countertop area. I can buy $2000 worth of goodies upgrades with the sales tax and registration fees hit for another coach. Stairs are not as steep. My pilots chairs were new leather when I got it. Cat 300 hp motor is simple, gets great mileage at 11 mpg, and more than adequate at 73 lbs/ hp. My exhaust brake works pretty good and service brakes aren't touched until under 35 mph on ramps and grades.
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: 91 u300 transmission retarder

Reply #9 –
Jor  ----  I think you are correct,  Now that you mention it, I remember reading that some where.  It doesn't seem to do much, but does help on long down grades.  Thanks and have a great day  ----  Fritz
Fritz & Kathy Johnson
1991 36'

Re: 91 u300 transmission retarder

Reply #10 –
At 10.4 liters, the big CAT engine alone should give you good braking on the long downgrades. Not quite twice a big as a 5.9 Cummings but almost there.

We have a ML320 weighing about 4800 lbs empty. The 3.2 liter engine is definitely on the small size for engine braking plus it's an automatic so pretty easy to heat the brakes with a trailer behind.  Our RAV4 engine is a little smaller but at 2900 lbs and a manual transmission, it has excellent braking. Heading east on I-70 and going down from the Eisenhower summit with a 7500 lb horse trailer behind us, the engine plus the aerodynamic braking from the trailer kept our speed down to 60 or so without using the brakes.

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

Re: 91 u300 transmission retarder

Reply #11 –
I use the tranny to keep my downhill speed under control and use the retarder to assist.  My Allison 4 speed has greater distance between gears than I would like, so I have to watch my RPMs when down shifting so as not to exceed top end.  The retarder works best at higher RPMs, so it is kind of a juggling match.  Thanks and have a great day  ----  Fritz
Fritz & Kathy Johnson
1991 36'

Re: 91 u300 transmission retarder

Reply #12 –
Our m11 is roughly the same displacement as a 3208.

300 vs 450.  743 vs 1450.  The in-line has the some of the same difference when used as a jake like the 3176 cats I drove.

Exhaust brakes are much less effective than jakes anyway. 

3208 exhaust brakes requires max revs to work
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: 91 u300 transmission retarder

Reply #13 –
My exhaust brake system has a exhaust back pressure gauge and a Morse cable throttling lever for the valve % closed, so I can adjust it on the fly to make it more effective at lower rpms. I have not used that feature so far, as it would be bad news if I forgot to move it back to the automatic position. Not sure if the gillotine valve has an orifice hole in it, as there is an external bypass piping. I have not tested yet since I got the gauge tubing fixed. Let off the throttle and engages automatically if unit is switched on. Even in town I could hear the leaking gauge tubing building pressure.
Old Phart Phred, EIEIO
89 GV ored 36' #3405 300 hp cat 3208 ATAAC side radiator, mountain tamer exhaust brake

Re: 91 u300 transmission retarder

Reply #14 –
Quote from: Caflashbob –
Our m11 is roughly the same displacement as a 3208.
300 vs 450.  743 vs 1450.  The in-line has the some of the same difference when used as a jake like the 3176 cats I drove.
But the CAT 3208 is physically a very small engine with a large displacement. While you can get a lot of HP out of them, the block because of it's size, does not have the strength for continuous high output applications.

You can install a 3208 in a Ford pickup truck without many size problems as many people have done. Try that with a 8.3, M11 Cummins or 6V-92TA Detroit.

24 second video here:

https://www.youtube.com/watch?v=c7jxoR-ey-Y
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)