Failure Analysis: Did a Baldwin PA2721 Filter Failure Kill our 8V71 Engine?

[luvrbus]

You lost me with the 1:1 final on V730 and no thanks I did a 4905 2 years ago  that was

1st   1.71:1
2nd  1.21:I
3rd  0.85:1
reverse 1.46:1

The up shift can be anywhere you want or done away completely we have no way of knowing what theirs was at least I don't and I always include the torque multiplication we went to the TC 470 converter with 3.25:1 the transmission  had a TC 490 2.51:1 and he thought it may be a little on the light side for a 40 ft bus living in the mountains

[RJ]

You lost me with the 1:1 final on V730.

Yup, that's a common thing with the V-730.  Lots of folk confuse the 3rd gear ratio with the (3rd x Bevel) ratio, but 3rd is actually 1:1.  Same as an HT-740.

I'll try to find my V-730 sales brochure that has the specs and scan it for you.

I'm not well-versed on the various torque converter ratios, but I can quickly see were in "unlocked" mode the torque multiplication can be significant between the different models. 

Speaking of unlocked, the shift sequence on a V-730 is 1C-2C-2L-3L.  Which is another thing that confuses folk not familiar with them - they think it's a 4-spd because the 2C-2L feels like a shift.

FWIW & HTH. . .



(Wow. . . Talk about thread drift!)

[luvrbus]

I have the V730 manual RJ no need to scan one,the V730 is just a 3 speed 740 a overhaul kit is the same for both only the bevel gear and shaft is the difference FWIW  

I have often thought about trying to use the 0.875 gear from a V730 on a 740 I know the bevel gear changes the ratio I was always told 7% but Allison says 0.875:1 with the bevel gear so now I don't know  

I do seem to remember there was about 4 different versions of the V730 when we were doing research    

The one I installed was V730D from a 1982 bus he wanted a V731 with overdrive but the electronic would have been a major chore on the 4095

thanks I learn something everyday

[chessie4905]

   The 740 doesn't use a bevel gear; only used because of the angle drive. The 4905 with 4.375 rear would have a high gear overall ratio of 3.83. Since the V730 doesn't have the low gear of the 740, it uses the torque converter to get it moving in 1st. (would be second in a 740, but somewhat higher gear or lower ratio because the bevel gear changes all the gear ratios in that trans).

[luvrbus]

I never said the 740 used a bevel gear I did say different but meant difference sorry and I corrected it

I am just going by what Allison says the final ratio is on a V730D and the starting is why I went to the TC470 torque converter  

When he wakes up I going to check with the Allison guru Bob Ware and see what he says is the final ratio on a V730D is if anybody knows it will be Bob not that I don't believe you guys but I want his opinion I cannot under stand why Allison would say 0.875:1   

[chessie4905]

   Definitely check with him but all V730 models had the overdriven angle drive ratio of .875 to one. In another words, if the engine turns 1 rpm, the trans shaft turns 1.14 turn or 7% more. I imagine that GM did this due to constraints of making the angle differential gears of lower numerical ratio than 4:11. Although the vs2's had two angle drive ratios; 1 to1 and 8.75 to 1. They never made optional ratios for the V730, after studying the parts manual. Some have claimed that there was an optional bevel gear ratio when the V730 first came out, but what's the point. The coach would lose 7% top end. The 4104's did have 3.875 and 3.55 ratios in an angle drive, however at a different angle. Maybe the design of the 4106 and on didn't have enough meat or clearance to go any lower in ratio or startability would have been insufficient.

[luvrbus]

Ok I got him while he was drinking his morning coffee and in a good mood  he says the V730 and the V731 have 3 different final ratios and 2 different bevel drive depending on what was spec and that transmission has other applications beside a bus that I did not know.

He says the two planetary gear sets produce the final ratio the bevel drive has nothing to do with the ratio and the 0.875:1 in lockup was the most common in the RTS they can have from 0.65 to 1.40:1 the 1.40:1 was used on a 6v71 engine in transit buses in some parts of CA he knew of

The 3rd digit in the model number will tell you the changes to the transmission that I knew, that is what he told me and now I am confused    

He did tell me I could use the V730 0.875:1 planetary gears on a 740 because he has done that for some Eagle owners that swapped to a 4 stroke Cummins he thought it was for B&B in Vegas he wasn't for sure on that, if nothing else I did get a answer on that part  

good luck  

[chessie4905]

I could see that different planetary ratios inside trans clutch units could effect the ratio spread of first and second, but it will effect the rpm drop of the engine upon gear change. Probably could be useful on a 4 stroke. My parts and service manuals are 1992's, so I'd like to get copies of the books on the new info, if they are still available.  http://groups.yahoo.com/neo/groups/RTS-bus-nuts/conversations/topics/11247
Here's some info from a few years ago:

[luvrbus]

Thanks I see where Geoff said the RTS had 2 different ratios for T series with a V730 I also read the Gurmman/Flx manual for the 870 transit it shows 3 different ratios for the V730 but I have no idea what GM used I used V730D from a RTS and shot the drive shaft with the wheel turning with my laser tach and could never make the math work to come up with 1:1 fwiw