[Archived]

I measure the amount of fluid I drain and then install the same amount. Then I adjust from there.

On your transmission it is very difficult to get a good reading off the stick on a fresh change of fluid because it is very difficult to accurately read the stick. It is best to read the stick when the transmission is up to temp and as you know that transmission really does not like to be overfilled so replacing the same amount that came out has always been the safest way for me to get real close.

I have read the stick multiple times until I am sure I am reading the fluid level correctly.

[Archived]

I would recommend you use a full synthetic fluid. Not entirely sure which type would be appropriate for your (type 755?) trans, but it could be determined from the fluid manufacturers. My old 755 would oxidize standard fluid fairly soon in high load/heat conditions.

[Dale]

What does that mean “oxidize standard fluid fairly soon in high load/heat conditions”.

I just put a new ratiator in and my engine runs at 180-195 but my trans oil temp seems all over and it will get to 230 while running for long periods.

I had looked at the trans filter and it leaking around the seal. I thought it might be getting dirty so it was putting more pressure on the trans. Just guessing though.

[Archived]

It is recommended by Allison that hand tools only be used on the bolts retaining the transmission filters.

This is to minimize the possibility of stripping the threaded bolt holes. Stripped bolt holes will cause you to have special thread inserts installed in the casting. That procedure costs ARO $11000.

( the inserts are specially designed and offered by Allison along with a drill jig. the pan must be removed for the procedure )

If Prevost or Allison perform the task their work is guaranteed, if you do it yourself and err you will also be buying a new pan.

OK, so you could weld it and remachine it and so it goes on and on.

This is all relative to my trans. a 6 speed on a series 60 engine in a 1996 chassis.

In some year after mine and to now all new transmissions have the inserts.

JIM

[Larry & Diane]

Remove the old filter and fill the new one with the same kind of fluid you already have in the rest of the transmission, whatever that is.

In my case we have a 1994 XLV with a 5 speed Allison transmission, I believe it is a model 740. it has been running on 30W motor oil for most of its life. The forst owner said the shifts were smoother. Since it works fine, I just kept using it.

As a side note, I have experienced the same problem twice now, that is a leaking spin on transmission filter. The cause is this. Drive in winter on sanded and salted roads ( like Utah in my case) and the tires kick up sand particles which hit the side of the tranny filter, this nicks the paint and corrosion starts. leave the coach parked a few months, come back and you have pinhole leaks in the filter. I believe it runs at 150 psi or so.

My solution is to change the filter after driving in salty conditions. On a truck, the parts are more protected it seems.

[Archived]

My 94 Liberty had the 740 and Allison told me not to switch to Transynd and keep using Dextron.

[Archived]

Dale…….The 5 speed transmissions will overheat if overfilled. And as I mentioned earlier it is very difficult to get the proper fill by reading the stick which unlike the 6 speed can be done at the keypad.

Before you change fluid (Dextron is recommended) see if you can get a good reading of the present level before dumping to see if it is overfull. The transmission temps as I recall should track the engine temps closely, and if you run in the rain you should see the temps drop considerably below normal temps in dry conditions. That characteristic was unique to my five speed, compared to the 6 speed which has an intercooler and a retarder.

[Archived]

I believe the 5 speeds have spin on filters; not the problem issues we have on the 6 speeds; shouldn’t be an issue to change. Pretty sure we used trans-synd in my 5-speed, pretty sure Prevost put it in. High temps will cause oil to oxidize (almost like evaporate) over time and reduce the oil level. When my 5 speed wouldn’t go into drive on cold starts until the oil warmed up (expanded), I knew it needed a quart or two added. Synthetic will give you lower operating temps (extending trans life and possibly reducing the load on your engine cooling system if you have a coolant to trans oil cooler) and extended drain intervals.

[Archived]

P.S. Trans-synd is ABSOLUTELY recommended by Allison for the HT and V 700 series transmissions; I believe my 1989 had a HT755 but I’m not positive. When my secretary gets back from lunch, I’ll see if she can post the Allison Service Information Letter.

[Archived]

I can’t attach documents supporting my statements, but if you want to send me your e-mail address, I will send.

[Ken]

I was getting ready to change my oil on
my Allison HT 754. I was looking at Castrol Transyd, Mobil Delvac
Synthetic ATF or Wolfs Head Oil, http://www.wolfshead.com/all are compatible with Allison specs.

I haven’t priced Transyd but Mobil is
$37+/- /gal. and Wolfs head is $18+/- /gal.

What do you guys think?

[Archived]

Dale,

I will yield to Joel’s statement that Allison is now recommending Transynd. That is later information than what I had previously that suggested Transynd was OK, but ecomomically unjustified. I know in his application pulling the weight he does it is important for him. Your trailer, depending on its loaded weight might be more than ample reason why Transynd is good for you as well.

If Wolf’s Head is meeting the same spec as Transynd or the others then I would be using it. On our six speed transmissions the use of Transynd (or equivalent) is clearly justified in view of the long drain intervals, but keep in mind almost all of us will run out of the calendar time interval before we reach the mileage interval called for. But Transynd is very pricey.

[Archived]

This info is from Allisons Mechanics Tips MT1366EN

[Archived]

OK Dale. Thanks. That is totally consistent with my previous understanding. If I can parse their words they are saying they would like you to use Transynd (it’s their proprietary brand and they undoubtedly make more money than if you buy Dextron from NAPA) but the other stuff is actually OK.

You have to do the math on economics and also consider the fact your trailer might be heavy enough to err on the side of caution. I think in light of the fact you use the trailer I would put in a fluid that meets the Transynd spec, if not Transynd. I use Transynd although the economics suggest that is the most expensive option, however I have a transmission retarder which drives up the heat on the transmission fluid so I opted to ignore the economics and consider the overall benefits.

Nothing is simple anymore is it?

BTW, your transmission as employed by our military is filled with 15W40 just like the vehicle diesel engines. The reason was in battle conditions the vehicles used the same oil throughout and it simplified service in the field. I am not aware of that applying to a six speed.

[Archived]

Interesting about the use of 15w40 in the field for the military. You really shouldn’t tell me those things, Jon…you know how I like to push the envelope on mods…you’re tempting me.

BTW, I don’t cange my ATF based on time. I don’t believe that’s really important unless you make short trips which don’t allow the trans oil to reach normal operating temps for long which would then promote condensation and sludge build up, of course. I just use the color/smell test. My GUESS is that trans-synd, in a coach used normally by a typical driver and not equipped with a retarder, may be considered virtually a lifetime fill.