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5.9 trans problem


bluegoat01

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Lately when my truck shifts in to OD I get what feels like a slip and causes the RPMs to bounce up and down. It even acts like this at around 30-35 mph sometimes. But mostly between 40-55 when the engine is running around 1500 to 1700 rpm. Any ideas as to what this may be?

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Maybe its not slipping as bad yet, then. Reason why I say that is because I do not think its your OD. I think its your TC because you say it happens at 2 diff speed sets. Which is actually where the TC locks/unlocks between shifting gears.

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Yes, sir. When I bought my truck, I had worse problems than you. The TC would cause the truck to shudder occassionally and it would slip when locking/unlocking. Hence the shudder. The slight blipping in your RPM would tell me IMHO, that your TC is beginning to slip. If its stock and the truck is new to you or you've been running it hard racing it around its possible to have done some damage.It can't be OD, because OD does not kick in until after 55mph IIRC. It does not shift in and out at different speeds like you explain. Only the TC does that.Do you know when the last time your transmission was serviced? You may be able to improve the problem more and gain some more life out of the TC if you service it. I would start by doing a full fluid flush, filter and bands. If you can, get Amsoil for the trans fluid.

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Well I'm the second owner and from what I can turn up the previous owner owner used it to haul a 5th wheel camper for most of its life. But I dont run it hard at all and the truck is mostly original despite having 217000 on the clock. But I'll give the full flush a try and see if it makes it any better. My only thing is my truck drops in OD as low as 40mph if I let off the throttle and thats where it really acts up is at those super low 1200-1400 rpm range.

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It can't be OD, because OD does not kick in until after 55mph IIRC. It does not shift in and out at different speeds like you explain. Only the TC does that.

Mine will shift into OD at around 45 mph. I understand that is a little hard on it to let it do that so I usually manually control that till around 55.

Well I'm the second owner and from what I can turn up the previous owner owner used it to haul a 5th wheel camper for most of its life. But I dont run it hard at all and the truck is mostly original despite having 217000 on the clock. But I'll give the full flush a try and see if it makes it any better. My only thing is my truck drops in OD as low as 40mph if I let off the throttle and thats where it really acts up is at those super low 1200-1400 rpm range.

OD not until 55? :stuned: My truck, with the OD off and at 55mph is about 2700rpm
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:ashamed: Hey, maybe I'm wrong. I'll have to check and see when mine hits into OD next time I'm cruising. For S&G's, before you look into the convertor thing, look into this: http://articles.mopar1973man.com/2nd-generation-24v-dodge-cummins/28-transmission-systems/260-torque-converter-lock-unlock-issues You could possibly be having a hunting issue? Dunno if your range of trucks is affected like our 2nd gens.
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  • 2 weeks later...

Ok so heres the update. Took a 50 mile trip down the freeway yesterday and it bucked me the whole way there while cruising around 70-75mph. Then today I've had no problems all day. Even when it bogs down in OD at like 40mph. I have no clue what to think of it now.

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Its going to become a little more complicated for me. I'm not very informed about CR trucks. I assume they have the 48re transmission. Not familiar with them at all. Hopefully someone can chime in on it. Best bet may be to atleast see if you have any PCM codes and/or take it to a shop if you do not get an answer on here. Depends on how badly you want it fixed.

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So my parts department at my work says his 00' Cummins had the same problem and the issue was the throttle positioning sensor. I'm planning on hooking up one of our high-end scan tools to see if I can get a code out of it. But its a $200 gamble vs a $1000 gamble.

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Well mine is an 01 but the sit. rep. as of now is that I'm suspecting throttle position sensor. We plugged in the scan tool and it showed that the TPS has 2 values as if its monitoring in 2 different spots. At closed throttle the readings were TPS1: 00.00 and TPS2: 9.76. At full throttle the readings were TPS1: 100.00 and TPS2: 77.6. They never matched at any point in between either. So its looking like I might have 2 sensors arguing over what gear to be in.

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Well mine is an 01 but the sit. rep. as of now is that I'm suspecting throttle position sensor. We plugged in the scan tool and it showed that the TPS has 2 values as if its monitoring in 2 different spots. At closed throttle the readings were TPS1: 00.00 and TPS2: 9.76. At full throttle the readings were TPS1: 100.00 and TPS2: 77.6. They never matched at any point in between either. So its looking like I might have 2 sensors arguing over what gear to be in.

That should be normal, if theTPS1 at 0 was at idle and the TPS 1 at 100.00 was at full throttle. Either way, the sensor is just a voltage. It isn't sending a varaible name like TPS1 or 2. Usually these sensors have a dead band in the middle of the range where they aren't linear, but are typically right at the ends of the range.
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