AC Transit

[Big CJ]

Here is something interesting.

http://www.polarinertia.com/march03/busses.htm#

I bet some of the 1200s and 1300s ended up here.

[Benjamin]

I think the HT740 and HT747 are equally fast: same gear ratios of 3.69 (1), 2.02 (2), 1.38 (3) and 1.0 (4). I think the only thing that makes one of these 740 variants shift faster is the shift point adjustment.

Some buses may have different rear end ratios: city buses are usually geared for up to 55 mph with direct-drive transmissions, so a 4.56:1 rear end is used on most applications; highway gearing for up to 65 mph is 4.1:1. Over-the-road coaches such as the MCI 9 series and the A/C series have a 3.73:1 rear end which really makes them go faster.

~Ben

Edited July 28, 2014 by Benjamin

[Big CJ]

I think the HT740 and HT747 are equally fast: same gear ratios of 3.69 (1), 2.02 (2), 1.38 (3) and 1.0 (4). I think the only thing that makes one of these 740 variants shift faster is the shift point adjustment.

Some buses may have different rear end ratios: city buses are usually geared for up to 55 mph with direct-drive transmissions, so a 4.56:1 rear end is used on most applications; highway gearing for up to 65 mph is 4.1:1. Over-the-road coaches such as the MCI 9 series and the A/C series have a 3.73:1 rear end which really makes them go faster.

~Ben

I think our Neoplans in Orlando likely had highway gearing. Some of those things could do 70+ depending on the bus itself. Not sure how fast the 40 footers or the 60 footers could go. Do you know the gearing for buses that use the V730/V731?

[Benjamin]

I think our Neoplans in Orlando likely had highway gearing. Some of those things could do 70+ depending on the bus itself. Not sure how fast the 40 footers or the 60 footers could go. Do you know the gearing for buses that use the V730/V731?

On the GMC RTS II and the Flxible Metro (and Grumman 870/Metro), the rear-end ratios are 5.38:1 city and 4.56:1 highway. Transmission gear ratios are 1.81 (1), 1.22 (2) and 0.875 (3).

The Ikarus 286 (the U.S. version of the 280) used a 4.3:1 rear end ratio for a top speed of 60 mph with the Cummins NHHTC engine and Allison HT740 transmission.

~Ben

Edited July 28, 2014 by Benjamin

[Detroit Diesel 6V92TA]

Here is something interesting.

http://www.polarinertia.com/march03/busses.htm#

I bet some of the 1200s and 1300s ended up here.

Holy moly! I want to go there now!!

I think the HT740 and HT747 are equally fast: same gear ratios of 3.69 (1), 2.02 (2), 1.38 (3) and 1.0 (4). I think the only thing that makes one of these 740 variants shift faster is the shift point adjustment.

Some buses may have different rear end ratios: city buses are usually geared for up to 55 mph with direct-drive transmissions, so a 4.56:1 rear end is used on most applications; highway gearing for up to 65 mph is 4.1:1. Over-the-road coaches such as the MCI 9 series and the A/C series have a 3.73:1 rear end which really makes them go faster.

~Ben

Hmm, do you know why the HT-747 typically makes buses have a higher sounding RPM than an HT-740?

[Benjamin]

Hmm, do you know why the HT-747 typically makes buses have a higher sounding RPM than an HT-740?

Shift point adjustment, as I said before.

~Ben

Edited July 30, 2014 by Benjamin

[Detroit Diesel 6V92TA]

Shift point adjustment, as I said before.

~Ben

Okay.

[bradfordbrian]

* i corrected per benjamin's information. *

Re: 740 vs 747, they have different internals, and do not readily interchange.

HT 740 and *747 have a hydraulic pressure-driven valved shift body.

* HT 748 has an electronic solenoid shift body controlled by the ATEC transmission controller.

The numbers do not denote shift ratios, they represent design variations.

* The shift points in the HT 740 and 747 are set-in at build time, and cannot be "adapted" without replacing the valve body of the transmission. This includes ratio maps. They can support a retarder on the output shaft which uses a separate controller.

The HT 748 shift points are electronically controlled, are in fact load-adaptive, and they can be modified through programming. The ATEC can skip gears, selectively engage the lockup in the torque converter, can interface with the engine brake and can autonomously control an integrated retarder.

Edited July 30, 2014 by bradfordbrian

[Benjamin]

http://www.dal-trans.com.au/Products/HT-740_-HT-747-1.pdf

Here's a 1987 HT740 and HT747 specification brochure. The HT747 was used for city and transit bus applications only, and was rated for up to 365 NHP (net HP) maximum and 1100 lb/ft max TQ. Vehicle weight max 60K GVW. Governed speed range 19/2400 RPM.

The HT747 is not electronically controlled but it can still be distinguished from the original HT740 by means of a forged lock-up piston for added durability and a three-gear oil pump to increase coolant and lubrication flow. Per the official Allison transmission history (per its website), it was introduced in 1982-83 for use in the transit coach industry.

The HT741 and HT748 electronically-controlled automatic transmissions follow the same logic; the HT748 is the one with the forged piston and triple-gear oil pump.

~Ben

Edited July 30, 2014 by Benjamin

[bradfordbrian]

http://www.dal-trans.com.au/Products/HT-740_-HT-747-1.pdf

Here's a 1987 HT740 and HT747 specification brochure. The HT747 was used for city and transit bus applications only, and was rated for up to 365 NHP (net HP) maximum and 1100 lb/ft max TQ. Vehicle weight max 60K GVW. Governed speed range 19/2400 RPM.

The HT747 can be distinguished from the original HT740 by means of a forged lock-up piston for added durability and a three-gear oil pump to increase coolant and lubrication flow. It was introduced in 1982-83 for use in the transit coach industry.

The HT741 and HT748 electronically-controlled automatic transmissions follow the same logic; the HT748 is the one with the forged piston and triple-gear oil pump.

~Ben

ahh... okay, well i was half-right.

i could have swore that atec was a major feature intro, but that didn't get rolled out until 1986

[coordinator47]

Muni's last buses to have an 8V71N was the 1975 AMG's (4100's). The rest were 6V92TA's as well (with a few exceptions). Now all of Muni's 6V92TA buses (1984-1991) had HTB-740 or 748's. How did the Flyer D901 feel compared to the Gilligs? Was it as smooth, rough, slower, faster, etc.?

Did the Neoplans have faux woodgrain on the inside?

The Muni 4100s had 6V71N engines and a two-speed V-drive transmission (VH-9?). They topped out around 38 MPH as they had the Muni standard 6 1/7 rear end ratio. A few (4109 which I rode, perhaps 4154, maybe others?) were retrofitted with what sounded and accelerated like a 6V92TA with a VS2 three-speed transmission.

About a year after delivery AC's 2400s and 2500s received a shift point profile change from economy and smoothness to maximum acceleration, upshifting near maximum governed speed. Prior to that they shifted just like Muni's D902s. Muni (as far as I know) stayed with the economy shift profile. I moved from the Bay Area to Seattle in 1989 and never rode a Muni D40. Nothing since the T8H-5305 accelerated from stopped with the urgency of those AC D35s and D40s.

The V730 transmission had a much sloppier feel when mated with the V903 engine than the 6V92TA. On the AC 1000s and the 1100s with the V903 there was a bit of throttle lag up to about 8 MPH and then they accelerated as well as the 2400s and 2500s. The 2400s and 2500s topped out about 61 MPH and the 1000s and 1100s were good for 65 MPH or more. The D901As locked up the torque converter in 2nd gear between 30 and 35 MPH and then shifted into 3rd gear around 40 MPH. On the D901s (1155 - 1169) the torque converter locked up in 2nd gear at 37 MPH or more. Some didn't lock up in 2nd gear at all and went straight into 3rd gear. The D901s were very smooth (see my comments from April 2013).

AC's 1000s, 1200s, 1300s and 2050s had a black and dark green hound's tooth upholstery fabric. The 1200s, 1300s and 2050s as I recall had woodgrain paneling.

[Detroit Diesel 6V92TA]

The Muni 4100s had 6V71N engines and a two-speed V-drive transmission (VH-9?). They topped out around 38 MPH as they had the Muni standard 6 1/7 rear end ratio. A few (4109 which I rode, perhaps 4154, maybe others?) were retrofitted with what sounded and accelerated like a 6V92TA with a VS2 three-speed transmission.

About a year after delivery AC's 2400s and 2500s received a shift point profile change from economy and smoothness to maximum acceleration, upshifting near maximum governed speed. Prior to that they shifted just like Muni's D902s. Muni (as far as I know) stayed with the economy shift profile. I moved from the Bay Area to Seattle in 1989 and never rode a Muni D40. Nothing since the T8H-5305 accelerated from stopped with the urgency of those AC D35s and D40s.

The V730 transmission had a much sloppier feel when mated with the V903 engine than the 6V92TA. On the AC 1000s and the 1100s with the V903 there was a bit of throttle lag up to about 8 MPH and then they accelerated as well as the 2400s and 2500s. The 2400s and 2500s topped out about 61 MPH and the 1000s and 1100s were good for 65 MPH or more. The D901As locked up the torque converter in 2nd gear between 30 and 35 MPH and then shifted into 3rd gear around 40 MPH. On the D901s (1155 - 1169) the torque converter locked up in 2nd gear at 37 MPH or more. Some didn't lock up in 2nd gear at all and went straight into 3rd gear. The D901s were very smooth (see my comments from April 2013).

AC's 1000s, 1200s, 1300s and 2050s had a black and dark green hound's tooth upholstery fabric. The 1200s, 1300s and 2050s as I recall had woodgrain paneling.

A 6V71N? I would also believe it would be 8V71N, due to the 1969 GMC's and Flxible's also having 8V71N. The wiki also says 8V71N, but you can't rely on everything from it. Now I am completely clueless on the transmission, but you are probably correct on it, due to the V730 not coming out until 1976. 4154 is the only one Muni preserved.

You are right about the 2400's and 2500's (D35's and D40's) having extremely smooth shifting. They sound like they would have been D60's in disguise. Muni's D902's (4500's) had HT-740 trans. while both AC Transit and Muni's D40's had HTB-748 trans. I heard that Muni's D40's were extremely smooth and fairly fast (similar to AC's).

I still don't know too much about the VTB-903. Was it a good engine (in your opinion)?

Which series of AC's buses do you think was the best? (I would guess the D40's).

[gmcfan949]

A 6V71N? I would also believe it would be 8V71N, due to the 1969 GMC's and Flxible's also having 8V71N. The wiki also says 8V71N, but you can't rely on everything from it. Now I am completely clueless on the transmission, but you are probably correct on it, due to the V730 not coming out until 1976. 4154 is the only one Muni preserved.

You are right about the 2400's and 2500's (D35's and D40's) having extremely smooth shifting. They sound like they would have been D60's in disguise. Muni's D902's (4500's) had HT-740 trans. while both AC Transit and Muni's D40's had HTB-748 trans. I heard that Muni's D40's were extremely smooth and fairly fast (similar to AC's).

I still don't know too much about the VTB-903. Was it a good engine (in your opinion)?

Which series of AC's buses do you think was the best? (I would guess the D40's).

the best? T6H-5307N. the 900s :-) in recent memory.... the MCI. it cascades down from there. the 903 engine was not a favorite of mine, but it could just be because it was in the D901 Flyers. I have a soft spot for the old Detroits up to the 6V92.

for sheer novelty we could discuss the pancake engine in the MAN artics :-) those were fun. each cylinder had its own head, so 6 per engine. they had a very distinctive sound compared to the 6V71s on the road at the time.

can you believe the Van Hools are at retirement age?? the 1000s and 2000s anyway... good riddance, I say :-)

[Detroit Diesel 6V92TA]

the best? T6H-5307N. the 900s :-) in recent memory.... the MCI. it cascades down from there. the 903 engine was not a favorite of mine, but it could just be because it was in the D901 Flyers. I have a soft spot for the old Detroits up to the 6V92.

for sheer novelty we could discuss the pancake engine in the MAN artics :-) those were fun. each cylinder had its own head, so 6 per engine. they had a very distinctive sound compared to the 6V71s on the road at the time.

can you believe the Van Hools are at retirement age?? the 1000s and 2000s anyway... good riddance, I say :-)

The Fishbowls eh? I like the good ol' New Looks as well, but something about those 1980's Gillig Phantoms, RTS's and D40's just shouts out awesomeness to me. So AC's D901's had 903's? People say those were only in D900's, but I am not truly sure what is correct. I guess I could start a section on the MAN engine sometime. Most (if not all) MAN artics seem to have had the same MAN engine in either 220 or 310HP.

I actually can't believe that 11 years is even considered the beginning of retirement. I guess the Van Hools are really "that bad." samTrans 1998 Gilligs hit 16 this year and are still running strong (even though I am sure they will be doomed for scrapping next year).

[gmcfan949]

The Fishbowls eh? I like the good ol' New Looks as well, but something about those 1980's Gillig Phantoms, RTS's and D40's just shouts out awesomeness to me. So AC's D901's had 903's? People say those were only in D900's, but I am not truly sure what is correct. I guess I could start a section on the MAN engine sometime. Most (if not all) MAN artics seem to have had the same MAN engine in either 220 or 310HP.

I actually can't believe that 11 years is even considered the beginning of retirement. I guess the Van Hools are really "that bad." samTrans 1998 Gilligs hit 16 this year and are still running strong (even though I am sure they will be doomed for scrapping next year).

okay...... I guess we fall in love with the bus design of our youth :-) to me the fishbowl defines an era and is the most beautiful ever built. the 'twinkies' (RTS) were appealing when they were new, but something about modern bus designs, when they go to seed, they REALLY look awful. of the modern varieties, the D40HF was nice looking. the new XD series isn't too bad either. looks solid.

13 years is the life expectency of any transit bus. it's how the depreciation and funding time things. by contract, the OEM no longer needs to provide parts after 13 years. for a district to look good on charts and with their community, 'fleet average age' needs to be around 6-8 years. the first NABI low floors are now 14. AC has held on to fleets past the limit in recent memory. depends on the type. like the 1900 D60HFs. they're only recently off the property--artics have been in short supply.

the Van Hools have just been a nightmare. besides they're an orphan. it's looking like a lot of Gilligs in AC's future :-)

re: the MANs, the AMG versions (first 1600s) were SG220, and the ex-SCCTD true MAN were SG310.

and yes, the 1000 New Flyers at AC, the D901s, were powered by Cummins 903 with a chain drive as delivered. they were converted to gear drive shortly thereafter. the chain sounded like they were going to leave parts on the road behind them. as I recall, toward the end of their service lives, it was becoming difficult to find parts for these things. the 903 had been discontinued.

[Detroit Diesel 6V92TA]

okay...... I guess we fall in love with the bus design of our youth :-) to me the fishbowl defines an era and is the most beautiful ever built. the 'twinkies' (RTS) were appealing when they were new, but something about modern bus designs, when they go to seed, they REALLY look awful. of the modern varieties, the D40HF was nice looking. the new XD series isn't too bad either. looks solid.

13 years is the life expectency of any transit bus. it's how the depreciation and funding time things. by contract, the OEM no longer needs to provide parts after 13 years. for a district to look good on charts and with their community, 'fleet average age' needs to be around 6-8 years. the first NABI low floors are now 14. AC has held on to fleets past the limit in recent memory. depends on the type. like the 1900 D60HFs. they're only recently off the property--artics have been in short supply.

the Van Hools have just been a nightmare. besides they're an orphan. it's looking like a lot of Gilligs in AC's future :-)

re: the MANs, the AMG versions (first 1600s) were SG220, and the ex-SCCTD true MAN were SG310.

and yes, the 1000 New Flyers at AC, the D901s, were powered by Cummins 903 with a chain drive as delivered. they were converted to gear drive shortly thereafter. the chain sounded like they were going to leave parts on the road behind them. as I recall, toward the end of their service lives, it was becoming difficult to find parts for these things. the 903 had been discontinued.

Yeah, I do like the look of the Fishbowls though. They do look really cool. About modern designs looking bad when they get old, SF Muni's Neoplan AN440's are starting to show signs of rust on the front end. I always liked the standard, yet tough look of the D40HF. I have never really cared for the D40LF as much and I honestly don't like the XD look. (It just looks really weird to me).

I guess 13 years just seems like an ultra short life compared to Fishbowls running for 26 years and Gillig Phantoms (of the past) running for 17-23 years. I wonder how samTrans has been keeping up their remaining 1998 Gilligs (600's) since they have Cummins M11's (not ISM's). They still look and run well though. When were the 1900 D60HF's retired?

I've luckily never been on a Van Hool. I guess AC is going back to their ol' reliable Gillig.

re: the MAN's. I didn't know AC had the AMG MAN's. That's cool.

re: the D901's (1000's). I could imagine it being be very tough since the VTB903 had been discontinued since the early 1980's.

[gmcfan949]

Yeah, I do like the look of the Fishbowls though. They do look really cool. About modern designs looking bad when they get old, SF Muni's Neoplan AN440's are starting to show signs of rust on the front end. I always liked the standard, yet tough look of the D40HF. I have never really cared for the D40LF as much and I honestly don't like the XD look. (It just looks really weird to me).

I guess 13 years just seems like an ultra short life compared to Fishbowls running for 26 years and Gillig Phantoms (of the past) running for 17-23 years. I wonder how samTrans has been keeping up their remaining 1998 Gilligs (600's) since they have Cummins M11's (not ISM's). They still look and run well though. When were the 1900 D60HF's retired?

I've luckily never been on a Van Hool. I guess AC is going back to their ol' reliable Gillig.

re: the MAN's. I didn't know AC had the AMG MAN's. That's cool.

re: the D901's (1000's). I could imagine it being be very tough since the VTB903 had been discontinued since the early 1980's.

I'm guessing the 'service life' issue didn't come into play until 'recently'. ie: gov't intervention into how long a bus is expected to last. since the 12-13 year 'standard', I have noticed manufacturers obsoleteing parts right at the 12 year mark.

agreed: the D40HF was a nice looking design. the XD60s that AC has, with that fairing along the roofline, makes the thing look like a bullet train. it's very solid and a good riding coach. I guess the face is something I'm getting used to thanks to the Van Hools--but the Flyer version is a bit more conservative. (must have learned their lesson after the Invero!)

the 1900s (New Flyer D60HFs) were officially off the property early this year. they were pretty much out of service sometime last year. the arrival of the 2190s (Van Hool AG300) and 2200s (New Flyer XD60) meant the end of the 1900s.

the AMG MAN 1600s were probably not noticed because AC had a tradition of not having the mfg's name or logo on their busses. unlike Muni, whose AMGs carried the bold logo, AC's did not. when the ex-SCCTD MANs and Ikarus showed up, they came with mfg logos, but it's been so long ago now, I don't remember if these were removed for AC service. it seems now that builders have gotten wise: they now cast their logos into the body panels.

[Detroit Diesel 6V92TA]

I'm guessing the 'service life' issue didn't come into play until 'recently'. ie: gov't intervention into how long a bus is expected to last. since the 12-13 year 'standard', I have noticed manufacturers obsoleteing parts right at the 12 year mark.

agreed: the D40HF was a nice looking design. the XD60s that AC has, with that fairing along the roofline, makes the thing look like a bullet train. it's very solid and a good riding coach. I guess the face is something I'm getting used to thanks to the Van Hools--but the Flyer version is a bit more conservative. (must have learned their lesson after the Invero!)

the 1900s (New Flyer D60HFs) were officially off the property early this year. they were pretty much out of service sometime last year. the arrival of the 2190s (Van Hool AG300) and 2200s (New Flyer XD60) meant the end of the 1900s.

the AMG MAN 1600s were probably not noticed because AC had a tradition of not having the mfg's name or logo on their busses. unlike Muni, whose AMGs carried the bold logo, AC's did not. when the ex-SCCTD MANs and Ikarus showed up, they came with mfg logos, but it's been so long ago now, I don't remember if these were removed for AC service. it seems now that builders have gotten wise: they now cast their logos into the body panels.

Yeah, it seems like another reason to throw away good stuff.

The D40HF was so cool looking that I actually went far enough to build a lego one (check out the "Lego Bus Thread"), I guess I would have to get used to seeing all of these XDE40's and XD60's around since those seem to be the only new NFI buses around here.

So pretty much they were done by 2012 and sent away by this year.

Why did they remove the logo's? I am not sure why, but I don't recall seeing a Neoplan logo on SF Muni's Neoplans. Only on the insides.

[Detroit Diesel 6V92TA]

It seems someone preserved AC Transit 2546 (1988 D40). It was seen at the Norcal Bus Fans Excursion this year in March. I don't know when their next excursion is though.

[gmcfan949]

It seems someone preserved AC Transit 2546 (1988 D40). It was seen at the Norcal Bus Fans Excursion this year in March. I don't know when their next excursion is though.

yes. I've seen it and it looks great. but for me, it's still too new to get too excited about :-)

in other news, the first of the new minibuses has shown up: 3501. it's a Ford. looks 'nice' from the outside.

[Detroit Diesel 6V92TA]

yes. I've seen it and it looks great. but for me, it's still too new to get too excited about :-)

in other news, the first of the new minibuses has shown up: 3501. it's a Ford. looks 'nice' from the outside.

Did you get to see the D40 in person? I know a well known dude named Kris has an AC Transit GMC New Look.

[AMG]

The 1980 built Flyers that were 35 and 40 feet long had Cummins VTB-903s and Allison V730 transmission. The 1982 Flyer D901s have 6V92TAs and Allison V730 transmissions. The Flyers started retiring in 1993 by the Gillig Phantoms and were completely retired in 1997 by the first order of NABI 416s. 2013 is preserved by AC Transit and I think is stored at the Hayward Yard.

The 1982 Flyer D901s had the Cummins 903. They had the smooth rear roof, as they never had AC.

Muni's last buses to have an 8V71N was the 1975 AMG's (4100's).

Those AMGs had a 6V71N.

[Detroit Diesel 6V92TA]

The 1982 Flyer D901s had the Cummins 903. They had the smooth rear roof, as they never had AC.

Those AMGs had a 6V71N.

You are correct on the AMG's having 6V71N's, as I recently read a 1984 Muni article. Those also had Allison VH9's as mentioned by someone else. I fixed the "8V71N" thing in the SF Muni portion of the wiki.

I have one question though, did all of AC Transit's 1980, 1981, & 1982 Flyer D901's have Cummins VTB-903 engines?

[AMG]

I have one question though, did all of AC Transit's 1980, 1981, & 1982 Flyer D901's have Cummins VTB-903 engines?

When they arrived, yes. But some were repowered.

I know at least one got a 6V92TA. And another one got a Cummins L10/Voith.

The Flyers that were sold to CCCTA were repowered with DDEC 6V92TA but kept the V730s.

[Detroit Diesel 6V92TA]

When they arrived, yes. But some were repowered.

I know at least one got a 6V92TA. And another one got a Cummins L10/Voith.

The Flyers that were sold to CCCTA were repowered with DDEC 6V92TA but kept the V730s.

Okay thanks for the info. I will add that to the wiki. It seems like most Flyer D900's and D901's had VTB-903's. Oh okay. Someone filmed a County Connection 1982 Flyer D901 in 1997 and it had a 6V92TA/V730. I didn't know those were from AC.