Engine/Transmission (1998.5 - 2002) Trans kickdown @70mph?

[RMarx]

I've recently noticed that my truck won't kick down on the highway with WOT applied at 70 mph. Is this normal? I have 3. 55's and stock tires so I'm at about 1900 rpm at this speed. It seems that with about 1300 rpm left to use it would downshift out of OD when floored.

 

[Lsfarm]

Not in Direct [3rd] gear

You have around 1200 or so RPM available in OD, but not in direct or third gear. Manually select OD off, and you will find that you are at around 27-2800 rpm in third gear, pretty close to redline.



This is why the trans won't downshift. It should downshift to third if you are at around 65mph.



Greg L. the Noise Nazi

 

[JPLB22]

Our trucks are the same except mine is a SB. Mine acts the same as yours, it will not kick down while doing 70. When I tow something that is somewhat heavy and I go up hill I will lock out OD with the switch on the lever. When I do that I try not to exceed 65 mph while in 3rd, at 65 mph in third I'm doin 2500 rpm. I know that is still 875 rpm short of redline but I don't like to push it much more than that. So I don't have a real answer for you except to say it is probably normal. If it did kick down it would be reving pretty close to 2750 at 70 mph.



Jeff



edit: The post from Lsfarm came up while I was typing mine and I didn't see it. Mine is just a long winded version I guess.

 

[RMarx]

Thanks guys, I guess its normal. In this case I guess I will post a seperate thread concerning lack of power at this speed.

 

[jjohn]

Hey RMarx

with the EZ on the lowest setting and RV275's 70 MPH has plenty of power..... I don't know where in CO you are, but if your around Denver and if you want to see for yourself... let me know.

JJ

 

[RMarx]

Jjohn-

Thanks for the reply and Nice truck! I'm in Loveland right now, but I get to Denver at least every week or two. Maybe one of these times we could cross paths and you can show your truck off to me? I'd be real interested to see what a modified cummins runs like.



Rob

 

[jjohn]

Rob

I saw your other post, any progress on your power loss?



Also I am north of Denver so Loveland is easy. I drove some TDR member trucks in the 400HP+ range "now I have an illness". Just a warning..... My truck is an infant in the power arena, still enough to spread the disease however.

JJ

 

[RMarx]

Jjohn-



No progress on power loss as of now. I put the silencer ring back in just to make sure this wasn't causing delayed spool up. It didn't make any difference. I might clean the MAP sensor today or over the weekend.

Can't wait to start bombing this thing!



Rob

 

[RMarx]

I pulled out the MAP and IAT sensors today and both appeared very clean (10k miles). I checked IAT at ~ 80 degrees and it showed 8k ohms. I think this is pretty close to normal right? I used a hair dryer to heat it up and the reading changed rapidly, seems to work the way it should.



Are there any tests for the map sensor or should I just spring for a new one and try it?



I took the truck out on the highway again today and it is a complete DAWG! It's strange because it accelerates very well on the on-ramp merging onto the highway but once up to speed(70-72mph) you can floor it on a very mild hill and it takes several seconds to gain 1 more mph. ???? There's no smoke that I've seen either under acceleration or flooring it at 70+.



BTW, it will kick down at an indicated 69mph, zooms up to about 2800rpm.