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99 vs 2001 auto trans

Discussion in 'Ram Trucks' started by dillyolboy, Feb 10, 2003.

  1. dillyolboy

    dillyolboy Member
    Messages: 97

    Does anybody know what the difference is between a 99 and 2001 automatic tranny in reguards to the unit that shifts the transmission? A 99 with the 5.9 liter and 4 speed automatic shifts about 800 rpm sooner in low range. A 2001 with a 5.2 liter and automatic tranny up shifts much later in low range and if you don't rev it past 2500 rpms or so it won't shift out of first gear. Is the difference in the motor or a change in the electronic unit that controls the transmission? On the 01 we played with the downshift cable and even disconnected it but it still up shifts in the same spot. It makes the truck almost undriveable in low range since you have to give it lots of throttle to make it shift. It might not sound like a big deal but with all our other trucks the tranny is in third gear within about twenty feet normally. This truck won't even shift out of first unless you hammer it and you can't get any speed cause it is in first gear so long.
     
  2. snowflake

    snowflake Member
    Messages: 86

    one thing you mite want to check is the t.p.s. that mite be bad or not at the right voltage and not settin check engine light off. had that problem on one truck volrage was off and not lettin it shift but no check engine light
     
  3. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    There are a few things that control the shifts on the Dodge autos,one of them is the governor pressure soleniod,Id suspect this may be the problem.How is it in high range? .The PCM knows the truck is in low range,and it should shift a little earlier in low range,it has a speed sensor on the OD unit,and it compares the signal to the one on the tailshaft or diff housing.If its in low range it has a different shift pattern. The engine,and trans temp also affect shift points as well.The TPS has an affect as well. I modify the dodge diesel auto's,the trans is much beefier,but the operation is similar ,almost exactly the same.Getting them to shift properly is no easy task,its quite involved and can be frustrating.
     
  4. dillyolboy

    dillyolboy Member
    Messages: 97

    Thanks for the responses. In high range this truck will not downshift at any speed unless you put it right on the floor. I don't know if this has anything to do with it but this truck works at pushing snow more than any of our other trucks. Like when you get the blade full of snow you can really hear it straining under a load that an old 5.2 w/Throttle Body Injection and 3.21 gears would walk away with. Here's another question I have always wondered about. What prevents the pre 96 trucks from shifting into overdrive in low range? It can be done. We had a 91 and a guy drove it through Mexico. It ran in low range the whole time. He hit a really big bump and the speedometer quit and the truck went into overdrive and it has worked perfectly ever since. It would be real nice since with overdrive you can go 50 pretty comfortably and now I have to shift into high range in three places on my route.
     
  5. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    Id change the gov solenoid,if tis under wartranty tell them its shifting weird,and thet should know exactly what to do after a few simple checks.These things are very common,I keep one in my inventory,for when I do a DTT install.The reason Od ont work in low range on pre 96's is the trans is the RH model,meanign it is hydraulic controlled.Unlike your newer ones that use a Gov solienoid in the valve body ,and a speed sensor to control the shifts,the 95 and older use a mechanical governor at the very rear of the OD unit.The OD function on the older ones is still electronically controlled,off the speed sensor,so if it doesnt see the neccesary speed at the tail if the t case(which it wont)it will nto engage OD.When the speed sensor fails usually you lose OD altogether,that is weird. My 2000 Ram goes into OD in low range.You can rig up a switch to force the shift into OD,but you have to turn it off when slowing down or it will stay in OD,while the front of the trans downshifts normally.This would not be good for the OD section,or the front either.I have done that with mine toying around,BTW 2nd gr/w OD is only 50-100RPm difference than 3rd gr:D . 1st with OD is close to 2nd.I hav the 4th gr switch in mine for dynoing and just to mess with.It makes it easy to dyno the truck like a standard.
     
    Last edited: Feb 11, 2003
  6. dillyolboy

    dillyolboy Member
    Messages: 97

    He had this truck into the dealership and the guy adjusted the downshift cable and told him it was the best that he could do. The truck does have a very long warranty though so he thought that would be a good selling point on a plow truck if he couldn't get it to shift right. Is there a way to "fool" the speed sensor on the older trucks? I guess it is fine now but it would sure be nice. We'll check out the governor solenoid. Thanks again.
     
  7. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    usually the trucks hunt for gears when the gov soleniod is going out too.You can tell him its hunting.It als sounds like the truck has turned up line pressures to me,thats how a 47RE acts with very high line pressures.
     
  8. dillyolboy

    dillyolboy Member
    Messages: 97

    Sorry John if I didn't make it clear. This is a 1/2 ton w/ the 5.2 liter so it would be a 46RE tranny. Correct? I don't know if that matters.
     
  9. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    I know that,the trannys are very similar,and react the same.