How Do I Tell What Transmission I Have???

Highway Yacht · November 01, 2010, 06:13:18 PM

Stupid question here.. Hows the best way to tell what transmission I have? I thought I had a 4 speed auto but noticed it shifts 5 times.. Could I possibly have a 5 speed or will the 4 speed feel like it shifts 5 times?? The shifter is a 5 speed shifter but the only gears that the shifter will physically go in are 2 thru 5. That is the reason I thought I had a 4 speed transmission with a 5 speed shifter. If I start off 5 it will change into 5 different gears. This bus originally had manual transmission but was switched out to an auto before I purchased it.

luvrbus · November 01, 2010, 06:38:24 PM

Look above the oil pan on the drivers side in the middle of the transmission there you will find a id plate the backup light switch will be close to id plate

good luck

RoyJ · November 01, 2010, 08:22:50 PM

Quote from: Highway Yacht on November 01, 2010, 06:13:18 PM
Stupid question here.. Hows the best way to tell what transmission I have? I thought I had a 4 speed auto but noticed it shifts 5 times.. Could I possibly have a 5 speed or will the 4 speed feel like it shifts 5 times?? The shifter is a 5 speed shifter but the only gears that the shifter will physically go in are 2 thru 5. That is the reason I thought I had a 4 speed transmission with a 5 speed shifter. If I start off 5 it will change into 5 different gears. This bus originally had manual transmission but was switched out to an auto before I purchased it.

Well, be careful, one of the "shifts" you feel is probably the converter locking. IIRC, the Allison 740 shift sequence is as follow:

1C, 2C, 2L, 3L, 4L

The 2 converter, to 2 locked, will feel like a shift.

thomasinnv · November 01, 2010, 09:52:00 PM

I have a 740 and it locks up at the top of 1st, just before shifting to 2nd. Now if I let it shift itself, it just mushes along (mushy, slushy...know what i mean vern?). I always shift manually though.

bruceknee · November 02, 2010, 03:22:41 AM

Do you have 2 or 3 pedals?

TomC · November 02, 2010, 09:37:47 AM

If you don't have any kind of production identification plate, it is relatively easy to tell the difference between the 4 and 5 speed 600 or 700 series transmission. If you look at the transmission case at the rear, the 4 spd has the tail shaft housing attached to the main case. On the 5 spd, you'll see the main case, then going back the 5th gear addition (about a 5 inch increase) then the tail shaft housing bolted to the 5th gear housing. If you have an output retarder, that too will be attached to the rear of the transmission, but will have cooling fins on it with two hydraulic hoses going to a trans cooler. If you have an input retarder, then you have an additional housing between the bell housing and the main transmission case with two hydraulic hoses coming out of it to a cooler. Good Luck, TomC

Highway Yacht · November 02, 2010, 02:06:05 PM

The ID plate is there but I can't make out any of the numbers. Here is a picture of what the transmission looks like. Can anyone tell what transmission it is by the picture?

luvrbus · November 02, 2010, 02:20:03 PM

The old reliable 740

good luck

Highway Yacht · November 02, 2010, 02:22:51 PM

Quote from: luvrbus on November 02, 2010, 02:20:03 PM
The old reliable 740

good luck

Thanks for the help....

Mike in GA · November 03, 2010, 07:29:07 AM

Yep, that's a 740.
The 750 series is longer and has a band of protuberances around its circumference that resembles a bandolier or belt of ammunition (at least to me).
Next week I am swapping out my trusty 740 for a rebuilt 750 close ratio. I do a fair amount of suburban and secondary road driving where 45-50 mph is easier to maintain with that extra gear.
Mike in GA

brettpearson67 · April 29, 2019, 02:41:16 PM

I just bought a new bus, a 1985 MCI 96A3, and I could've sworn it shifted 4 times, at 10, 22,28, 42ish, but it certainly looks like the 740, not the 750.
What could make it feel like a 5 speed?

Thanks
Brett

richard5933 · April 29, 2019, 02:53:54 PM

Are you perhaps feeling the toque converter going into lock-up mode?

brettpearson67 · April 29, 2019, 03:54:29 PM

Well, I suppose that could be it. I don't know anything about these trannies.
Is it that noticeable?

Iceni John · April 29, 2019, 07:41:07 PM

Quote from: brettpearson67 on April 29, 2019, 03:54:29 PM
Well, I suppose that could be it. I don't know anything about these trannies.
Is it that noticeable?

Yes! When my 740 locks, there's more jerk than when it shifts between gears. It almost seems like there's also more RPM drop when locking, but maybe I'm just imagining it.

John

TomC · April 29, 2019, 10:19:30 PM

That is an HT740. The HT754CR has an extra gear bolted on the back of the transmission-of which this transmission pictured does not have.
Typically the normal shift pattern is- 1st converter, 2nd converter, 2nd torque converter lockup, 3rd locked up, 4th locked up. Good Luck, TomC