Codeblue242
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So I bought a Stewart and Stevenson m1078 awhile back and just like my old 5ton it shifts hard in and out of first with the granny gear. Is there a way to lessen the jolt?
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M1078 hard shift
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Ronmar
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Whats your idle RPM? Is it storing any codes? Does it both warm and cold? What year?
glcaines
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My M35A3 with an Allison 1545 transmission also shifted up and down hard until I switched to Dexron 3 ATF. The change made all the difference in the way the transmission shifted - much smoother.
Codeblue242
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I will have to look at rpm and warm and cold yes.
Codeblue242
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So was yours banging in and out of first as well?
glcaines
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Yes. When I would come to a stop, the transmission was still trying to pull and then it would make a bang and downshift. Upshifting was the same. After the change to Dexron 3, no more of that nonsense. I've put thousands of miles on mine after the switch to Dexron 3 and zero problems. The transmission now operates as smooth as the trans in my F250. I did multiple flushes, driving in between shifting up and down to make certain I got all of the engine oil out of the transmission and torque converter. Engine oil and ATF are not compatible. I purchased the Dexron 3 equivalent from NAPA in 5 gallon pails. I was told that Dexron 3 equivalent from NAPA was the same as Valvoline brand, but a whole lot less expensive.
coachgeo
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Not good 24v will cause funky issues. Also ... am thinking a resent discussion mention throttle position sensor too cause shift issues??
It was a sticking throttle pedal not returning to idle. Lube the hinge and/or the cable itself to allow engine to return to idle when pedal is released.
Now see here:
LMTV M1078 Transmission Fluid Change To ATF Write Up
Did the switch from the 15w40 engine oil in the transmission on my 1997 M1078 LMTV with WTEC II to ATF. Followed "8-9 Transmission Oil Filter Replacement" procedure found in TM 9-2320-365-20-3 page 8-32. However, I deviated from the procedure and did NOT remove the front driveshaft (WARNING...
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Ronmar
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Someone
someone else had a bad position sensor, but that was hard shifting while driving. I get the impression from the OP that this happens when he enters 1st gear using the buttons on the control. 1st uses that P6 clutch pack up under the rear case of the transfer, but other than it’s location it should engage like any other gear. It being such a large jump in ratios between 2nd and 1st a little bit of excess RPM would really make a difference… he also didn’t mention if he had any stored fault codes in the transmission controller(press up and down arrows together, then press mode to step thru d1-d5 memory locations)…
Codeblue242
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That would be my worry thinking I got all of the oil out and then adding transmission fluid into it
That would be my worry thinking I got all of the oil out and then adding transmission fluid into it
Codeblue242
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Thanks
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As mentioned earlier.. make darn sure your transmission is getting the proper 24 voltage..right Ronmar !..lol…. … as for transmission fluid.. I had a retran installed about 6 months ago…Momma Allison stated , rather sternly, that under no circumstances is the transmission to be filled with 15w-40 or any other ATF other than Transynd…. Otherwise the 2 year warranty would be voided… needless to say Daytona Cat RingPower , who completed the install , big kudos to them, also advised that any Caterpillar equipment with an Allison must use Transynd…. Not sure about the “science” or if it’s a marketing ploy, behind it , but Transynd it was…. 6 months later the transmission shifts 10x better , slightly aggressive up shifts and smooth downshifts….and that break your spine downshift from 3rd to 2nd….long gone. The only downside is the cost… @$600-$1000 depending in the number of flushes required…. Bottom line , the Transynd has been fantastic for my application…others may differ…
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I see what your saying, but then why does the Allison website show other recommended fluids for their transmissions?
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hmmmmm??... interesting...the fact that Allison has its own Transynd....marketing ploy?...I see what your saying, but then why does the Allison website show other recommended fluids for their transmissions?
glcaines
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I previously talked directly with an Allison engineer at the factory when changing out the motor oil in my M35A3 allison transmission. He told me that Transynd was a very good fluid, but that Dexron 3 was just as good for most situations. He said the only advantage of Transynd was the longer mileage interval for changing fluid than standard ATF. He told me not to use Transynd unless I didn't mind the extra cost. He also warned me that transmission shops would try to sell me on Transynd because they made more money selling Transynd.
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My 2008 A1R with the gen 4 Allison shifts quite nicely with (what I assume to be original) 15w40 in it. And the fluid is so clean I have to look hard to even see it on the dipstick. Wiping it on my finger it literally looks like it's brand new right out of the bottle. Truck has 6500 original miles on it. 3500 of that has been from me.
I haven't decided if I'll change it out or not.
I haven't decided if I'll change it out or not.
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You can spend $25 for oil evaluation and not worry. I use Blackstone and have saved hundreds. My trucks shift fine with 15W40.
Same experience here. As long as you choose a fluid which conforms to their spec, you should be good. The fluid I used was certified to their TES 349 spec.
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Another side question here, I checked my codes and I have only 2 showing, a "power interruption" (from the previous brownout, and a "ECU high input voltage" (presumably from the same outage). Thing is, I have an intermittent issue where on downhills (again when it's cold) the trans downshifts 1 gear from 7 to 6 rather hard, then displays "check trans". My foot is off the throttle at this point bc I'm rolling down a 6% grade. But when I pull over and come to full stop the light goes away and the trans feels like it shifts, then the display goes back to 7 and all is well for the rest of the ride.
I tried it again yesterday to see if I could repeat the issue but it did not exhibit the problem however I had already done the "rapid warm up" procedure so the trans was probably warm.
I've only had this happen 2x and both times the trans was cold (ie no warm up procedure).