Auto transmission - Double "bump" engagement?

[Cooker]

I think this is the best forum for this, as it applies to both the 12v and 24v automatic transmissions.



I recently had the transmission rebuilt in my '96 4x4 2500. I had the shop install a DTT VB/TC combo along with all the other necessary parts to completely rebuild the transmission.



My question is this: Before the rebuild I had a double engagement into drive (or any forward gear) when moving the shifter from P or neutral. The best way to describe it is a double "bump" of engagement. It was very quick, perhaps . 5-1 second. It would bump and begin to roll, but are not able to accelerate until the second bump. If you stepped on the pedal in that split second, the motor would rev and the transmission would hook up on the second bump.



I still have this double bump after the rebuild. Bill K. informed me that this is somewhat normal for the Dodge trannys, but the way he personally rebuilds them, it eliminates this problem.



Does anybody else have this problem?



Your comments are much appreciated.



Thanks,

Ryan

 

[Dieselnerd]

I've never noticed a double bump on mine.

 

[DavidGardner]

I too have the Bill K. modified auto . Bill Did it himself while I watched. My trans will not engage reverse when I place the gear selector in R, until I speed the engine up a little. I took it back to him once for this but it still does it. Maybe my idle is set to low? Any way I have just learned to live with it. Other than that I love the mods. See my signature.

 

[illflem]

No double bump for me ever.

 

[John_P]

Ryan:



My ENTIRE transmission was rebuilt about 12,000 miles

ago by Scheid Diesel. I have never had the "double

engagement" you speak of either before or after the

rebuild. I would give Bill K. a call and ask him what

can be done to correct your problem. All the members

that have his products speak highly of them and of

his technical assistance. I am sure it is probably

a minor adjustment of some type.



----------

John_P

 

[Cooker]

Talked with Bill a little more about the issue. Just to clarify, the problem is not related to Bill's product in any way. From what I understand the problem is with the pie plate in the transmission. I really don't know how to explain it all that well, but it is not related to the VB or TC.



Bill said about 40% of the customers that come into his shop complain of this. He knows what causes it and how to fix it, but the shop that did the work for me doesn't. To fix it, the transmission needs to come out again, &#%$. It really does irritate me. To the point, I'm going to see if I can work something out with the shop to repair it per Bill's instructions.



I was under the impression that a rebuild would fix it, apparently not. I was just wondering if anybody else out there in the world of the mighty Cummins is having this same problem.



Thanks fellas,

Ryan

 

[Dreher]

I had the exact same problem on my 96. I never tried to accellerate between the engagements but mine would do it in drive or reverse. Put it in gear and get two very distinct engagements. About six weeks ago, I had Bill do a complete rebuild at his shop. You should have seen Vinnie's eyebrows go up when he put it into gear. The new trans is great but I can still feel the double engagement at times, though it's been reduced about 95%. I have a feeling that some of this may be due to slop in the transfer case (113,000 on the truck). I have some slack somewhere and I think that is the next place I'm going to look.



Bob

 

[Bill Kondolay]

Ryan,



The double bump that you are describing is usually caused by a weak dampner spring (pie plate, return spring, diaphram spring) in the rear clutch drum , or check ball within the piston is a little sticky.



Most Dodge rams have some sort of a double bump engagement in the earlier model dodges. Chrysler does have a update on that return spring ( Chrysler's term for the part) .



I or my dealers do not use the after market one , we use the Chrysler one. Most guys may not feel the double bump, but they do have some per the way the system was designed. As oil is fed into to the drum, it pushes the piston, and the piston then pushes against the apply plate which engages the clutches to apply 1st gear. While the oil is actually pushing against the piston the check ball is seated into its pocket thus sealing the piston area.



If there is not enough tension on the return spring the check ball does not actually seat until there is more tension, that is why you get the double bump.



Basically , the first bump you feel is the piston pushing against the spring and the second one is the checkball seating.



It could also be a check ball pocket problem, in which case the rear drum piston would have to be replaced.



The opposite of what you are feeling is when you go from drive to neutral, you feel it hold the gear for a fraction of a second. It is another sign of a weak dampner spring. The dampner spring has to push the piston back against the drum in order to release 1st gear. Part of that oil is being released through the check ball in the piston so it takes a while for that oil to exhaust.



Would i take a trans out just to replace a pie plate for a double bump engagement, no i wouldnt because it wouldnt it wont cause any damage. However if it annoyed the customer we would do it.



Ryan i would say, because the double bump is half of what it was before they rebuilt the trans , i would guess they have already changed the pieplate and they may just have replaced it with an aftermarket one, i would ask them to also look at the check ball in the piston.

 

[SteveAZ]

I've had problems (One the 1st transmission) with no or zero bumps, or lots of bumps over 45 MPH. But never a double.