I have a 4104 and I think that if I swapped in a v730 auto trans I could get better fuel economy.
I plan to install a turbo 671. the 4spd has a 1 to 1 angle drive and the v730 has a .875 to 1 angle drive.
I have a 4.125 rear axle and run 11r 22.5 tires.
This would reduce my rpm by 12.5% say 200 rpm.
So my question is will the v730 fit behind the 6L71?
Is the bellhousing in the same location as the 4106?
Looking at the 4106's (without measuring) it looks like the bellhousing may have the same position as the 4104 because the 4106's have the muffler between the radiator and the engine.
Has anyone done this already?
Any thoughts?
Thanks,
John
John,
I don't believe that you'll get any better fuel mileage from the change to an auto! Most auto trannys are far inefficient compared to a manual because the manual is a direct gear to gear drive, while the auto has the torque converter, and clutch packs that lose/use power so even with a slight overdrive on the auto it'll be less efficient than the manual. FWIW ;D BK ;D
1. the V730 is approx 20% less efficient than the Spicer 4 speed.
2. With the instalation of the V-730 you will have to change the rear end as well as the angle of dangle is different
3. With the instalation of the V730 you will have increase engine temp so your cooling system will have to be upgraded
4. With the instalation of the 6-71T you will have increased need for cooling as well
can the v730 use a separate cooler so not to tax the original 671 cooling?
Thanks for the input guys!
Quote from: johns4104 on February 01, 2009, 02:59:37 PM
can the v730 use a separate cooler so not to tax the original 671 cooling?
Thanks for the input guys!
Yes, an oil to air cooler can be installed. Jack
There is a member on this board that has done several 4104s. I hope he doesn't mind me showing some of his work. Truly exceptional craftsmanship.
4104 8V71TA/730 and one photo of a 671 with a v730.
The rest:
Can you all guess which bus nut it is?
Barn owl thanks for the pictures.
I love bus pictures!
John
They do make a 6-71TA block-but very hard to find. Rebuild your 6-71 into a turbocharged engine with air to air intercooling (mount the intercooler in the transmission door). With 80 injectors (the highest Detroit made from the factory) you can get 300hp with 900lb/ft torque. With the V730-a serious increase in torque-like 50%! The inline 2 strokers are much more rugged than the V blocks since they have just one cylinder running off the crankshaft throw compared to 2 cylinders per crankshaft throw on the V blocks. Personally, I'd feel safe running 90 injectors in a turbocharged and intercooled 6-71 for 340hp and over 1000lb/ft torque! Course you could achieve the same results by using a Cummins ISL through a reverser gear and have 425hp and 1200lb/ft torque, and quite possibly close to 10mpg with it. Good Luck, TomC
John.
When I put an v730 in my 4106 it cost me about 1and1/2 miles per gallon. I have been told that a v730 takes about 35horse power to pull plus generating some heat. But it sure is nice in traffic.
Roger 4106
Hi John,
Our 4104 with a 8V71 and 730 has the transmision cooler outside of the radiator, also the rear end was swapped for one out of a 4106 because the drive angle is different. Doesn't the 730 have a lock-up converter? I would think there should not be an efficiancy difference from a manual when locked up. We averaged 8 mpg in the 3000 miles we have driven it .
Bob
Yes the V730 has a lockup torque converter, but-and this is straight from Allison- a planetary gear transmission with clutches will always have a drag on it because of the transmission fluid circulating between the disengaged clutches and gears engaged. Granted, on a manual transmission you do have some drag, but the automatic is more like about 20hp with the V730 the worst with its' bevel gear. Even with that, I still think the Allison transmissions are the best for our application-there is no other transmission that will accelerate from 0-40 like a fully automatic transmission with a torque converter. Hence-also alot more heat rejection at all times. Good Luck, TomC
johns4104,
This is off the subject, the picture in your post (the black truck, bus behind it) did you at some time tow your bus with that
truck? I remember a few years back seeing this on the road when I was out west! Didn't mean to hijack your thread.
Steve 5B......
Roger, I would be changing the bevel gear from 1 to 1 to .875 to1 I am not starting with the same overall gear ratio as the 4106
Steve5b Yes I did tow my parts bus home from mineral wells tx.
Bob Yes the v730 does have a lock up converter. As mentioned the auto has more drag internally than a manual trans.
In theory AT always have lower ratio rear ends so they should get better mileage in lock up.
In practice there is so much slippage getting to the lock up stage that the mileage is probably always lower. An extreme case in which the AT goes for thousands of miles in top gear lock up would give better mileage, but that never happens.
Slippage also generates a lot of heat which is fuel vanishing into thin air.
I think lock up is powered by hyd pressure so the hyd pump also uses a bunch of energy.
The only energy loss I can think of for a manual box is some of the gears turning around in oil and the trans oil pump circulating oil, but that would not be much.
Short GMC Powertrain History Lesson - (There will be a test!!) :o
GMC designed the powertrain around tires that turned 495 revs per mile, going all the way back to the pre- and post-war Silversides. With the 1:1 bevel gears, this gave 60 mph at 2100 rpm. This combination was perfect for the time period, when the Interstate system was still on the drawing boards, and most highways were still one lane in each direction. A few freeways existed around major metropolitan areas, but that was the exception, rather than the rule.
Fast forward to the late '50's. President Eisenhower authorized the Interstate system, and the freeway race was on. Greyhound had their Scenicruiser on the roadways, but was unhappy with it's twin 4-71s powerplant, and was experimenting with other combinations. Come late 1959, when the "New Look" or Fishbowl transits was introduced as 1960 models, along with them came the first V-block 71s - the 6V71. This was followed in 1961 with the introduction of the 8V71 in the PD4106, and as an option with the transits. Greyhound immediately cycled all remaining Scenics thru Marmon-Herrington to get the new engine and other modifications. The 8V71 was a hit, and became the engine of choice for the bus industry over the next two decades.
One of the things GM discovered while doing development work on the 8V71 for the highway models was that the increased torque of the 8V, multiplied by the gears in the transmission, would blow out the bevel gears. This is why the bevel gear sets on subsequent models, both transit and highway, are before the transmission, not after, like the 4104's. By placing the bevel gears first, they were better able to withstand the greater torque output. A side effect of this, however, was that the engine/transmission powerpack had to be shifted slightly, and the rear axle pumpkin moved to the opposite side of the coach centerline, in order to maintain proper u-joint angles during operation, or they, too, would be short-lived.
Now remember, GM was still using tires that turned 495 revs per mile for their development work. Because of the additional torque available, the engineers discovered that they could overdrive the bevel gears somewhat, while using the same basic internal transmission ratios that had worked so well up to that point. This lowered the engine rpm at any given road speed, thus giving the 4106 virtually equal fuel mileage at 60 mph compared to the 4104. Turns out, this is translates to a 450 rpm drop, because the 4106 runs 60 mph at 1650 rpm with these tires, compared to the 4104 running 2100 rpm at the same speed. Fleet operators liked that, a LOT, since they were paying the fuel bill! (So did the drivers - because the 4106 would flat get up and MOVE next to the '04, thus negating the equal fuel mileage claims. One reason so many '06's out of the factory were governed at 1700 or 1800 rpm initially!!) Thus all subsequent GMC manual transmission buses, be they transit/suburban or highway models, were equipped with an 0.808 bevel gearset. Coupled to the 4.125:1 rear axle, this gave an overall 3.333:1 final drive, compared to the 4.125:1 overall of the earlier models.
(This "tall" ratio is also why reverse seems way too high a gear for our purposes, but you must put that, too, into perspective. It wasn't designed for wiggling into a campsite at Oh Dark Thirty - it was designed for backing out of a flat & level bus depot parking stall. It's that simple. Perspective, folk, perspective!)
Note that when the 40-foot 4903s came out, because of their increased weight over the 35-foot models, the rear axle ratio was changed to 4.375:1, yet the bevel gear ratio remained as is. About this same time, the 12R22.5 tires started becoming the standard tire on buses, yet they stuck pretty close to the original 495 rev/mile overall sizing. You also have to remember that the V-730 was originally developed for transit use, where operators are more interested in 0 - 30 mph, but with occasional short runs on the freeway. Thus the bevel set came with the 0.875:1 ratio, as a compromise for both types of operations, city & freeway. There's an urban legend out there that says you could also get a 1.04:1 bevel set in the V-730, but in my 29+ years in the industry, I never saw one. If it, in fact, did exist, my guess is that you'd have only found it in early production runs coupled to the lower-powered 6V71 engine, and only installed in transit buses for operators like San Francisco's Muni, where hill-climbing ability is important.
So much for the history lesson. I think you can see, just from my short (?!?!) dissertation, that there's a lot more that goes into all this than simply slapping on a particular tire size or choosing an arbitrary transmission ratio.
John -
So how does this affect you? Let me illustrate with a real-world example:
There was a fellow about 10 years ago here in Fresno that did exactly what you're wanting to do - install a V-730 in a 4104, behind the stock 6-71 (non-turbo in this case), and using a rear axle out of a 4106. I visited with him often during the change-over, so was pretty familiar with what was going on. He did a beautiful job, you'd have thought it came from the factory that way when it was finished.
I talked to him again, after he got back from a trip to Texas, to see how it all worked out.
His first comment, when asked about the trans swap, was basically "Worst damn mistake I've ever made in my life!"
Elaborating, he said around town it was fine and a lot easier to drive, but on the highway the bus couldn't keep up with traffic, would climb the 6% grades we've got around this valley at 15 - 20 mph, as opposed to 30 mph with the stick, and his fuel mileage dropped from 10-11 down to 7.5 - 8.
He kept it another two years, but never made any long trips again, until a stroke took away his ability to drive and he sold the coach.
Last I heard, it was in the Oxnard/Ventura CA area, where the owner pulled the 6-71 and installed a 350 hp 6V92TA.
A 6-71T puts out just about the same HP/torque as a stock coach (not truck) 8V71, so those folk who have given you numbers for their buses with the stock engine hooked to the V-730 are very real world.
Your numbers do pencil out that theoretically you should get better mileage, based on the gearing, but reality isn't the case. Too much loss in the automatic.
OTOH, if you were to switch to 11R24.5 tires, and bought the ones that turn only 470 revs per mile, as opposed to the 502/504 your current tires are turning, you'd pick up some of that mileage loss attributed to the Allison.
But it still wouldn't equal the mileage you're getting with the manual box now.
If you really want an automatic, the best bang for the buck is a 6V92TA bolted to the V-730. Pump the six up to 350 hp, and you'll have plenty of power for climbing Rocky Top, and still get around 7.5 to 8 mpg - especially if you also invest in the taller 11R24.5 wheels & tires.
FWIW & HTH. . .
;)
Quote6V92TA bolted to the V-730. Pump the six up to 350 hp, and you'll have plenty of power for climbing Rocky Top, and still get around 7.5 to 8 mpg - especially if you also invest in the taller 11R24.5 wheels & tires.
My father's 4106 has that setup and it is exactly what RJ says. Simply wonderful!
RJ, Sounds like what I need to do is run a 4106 trany and rear axle with my 671t.
Thanks for all the info
Quote from: johns4104 on February 05, 2009, 07:23:01 PM
Sounds like what I need to do is run a 4106 trany and rear axle with my 671t.
John -Do you already have the 6-71T?
If so, pull out the measuring tape, as you'll have to do a lot of number crunching to see if this would work.
If you don't have the 6-71T, then simply swapping in a complete 4106 powerpack would be a lot easier.
Don't forget to upgrade the cooling system - the '06 radiator's a whole lot bigger than the '04's.
FWIW & HTH. . .
;)
RJ,
Yes I already have the 671 it is a fresh rebuild setup for a turbo.
Thanks, for all the info it gives me lots to think about.
I guess I need to get my conversion (interior) down first before I tackle the drive train.
The 671 with a 4spd runs good.
John
Just planning my moves!
Quote from: johns4104 on February 06, 2009, 07:19:50 AM
The 671 with a 4spd runs good.
If it ain't broke - Don't fix it!! ;)
Thats right RJ keep it simple!!! :D