Won’t go past 55 mph and revs high while driving.

[JoeJoe_91]

I’ve had this CUCV M1009 for a few years now, and it’s ran at Highway Speeds (65-70) with no problem until recently. It wont’t go past 55 mph even when I’m going down a huge hill, and it revs really high every minute or so while driving it at 55. It also seems to shake a lil bit when I’m at 55mph, it never did that before all this started.

Replaced:
Transmission Filter
Kick Down Solenoid
Vacuum Modulator - Old one was STOCK (I’ve tried adjusting )

Checked:
I cleaned my CDR Valve (Soaked in gas overnight)
STOCK Vacuum Lines (I’m gonna replace soon)
I shifted the Vacuum Regulator forward a 1/4”

Any ideas as to what I should check, clean, or replace? Any and all help would be much appreciated, I’ve never had to take it to the shop for any of the work I’ve done to it. I’m not an expert on the 6.2 Diesel, but I’ve learned a lot the past few years from this website alone. I’ve tried everything I can think of, I came here to ask the experts before I destroy the truck since it’s my daily driver.
View attachment 898476View attachment 898477

 

[87cr250r]

If it's down on power and surging start with the fuel filter.

 

[JoeJoe_91]

I’ll try to drain the bowl and see what it does until I can order a new one, it is definitely dirty though. I changed the in-line filter I have right before the spin on, and the color difference is ridiculous. I definitely neglected the filter though, I hope that’s the problem and I didn’t mess anything up driving it. Thanks for the quick response, that one stares me in the face every time I open the hood and didn’t think nothing of it.

 

[JoeJoe_91]

I’ll wait for a new filter before trying to drive again.

 

[nyoffroad]

Maybe fuel related, but the "revving real high" has me thinking other wise. Could it be in 2nd gear? Don't go by the PRNDL actually count the shifts.

 

[JoeJoe_91]

Maybe fuel related, but the "revving real high" has me thinking other wise. Could it be in 2nd gear? Don't go by the PRNDL actually count the shifts.

I wanna say you’re right about that, either it was hard to tell or it didn’t go into 3rd at all. It shifts fine going into 2nd around 15 mph (something like that), but once I reach 50-55 it just stays there even with my foot to the floor. When it does rev up it doesn’t do anything but make the rev noise, it doesn’t go any faster and the engine doesn’t jump or anything. I stop the revving by letting off the gas a little. It cranks on a dime, idles fine, drives great until I reach 55. I used to drive an hour to town going 65-70 on the highway, so I definitely think it’s not shifting into 3rd for some reason.

 

[87cr250r]

You need to replace the filter. The sediment in the bowl isn't clogging it.

 

[JoeJoe_91]

You need to replace the filter. The sediment in the bowl isn't clogging it.

I’ll have it tomorrow, just ordered it on Amazon.
That was just a reference to show what the filter is clogged with.

 

[Valley Rock]

Personally I'd unhook the vacuum line down at the modulator while it's running and verify a vacuum signal .

 

[WWRD99]

I wanna say you’re right about that, either it was hard to tell or it didn’t go into 3rd at all. It shifts fine going into 2nd around 15 mph (something like that), but once I reach 50-55 it just stays there even with my foot to the floor. When it does rev up it doesn’t do anything but make the rev noise, it doesn’t go any faster and the engine doesn’t jump or anything. I stop the revving by letting off the gas a little. It cranks on a dime, idles fine, drives great until I reach 55. I used to drive an hour to town going 65-70 on the highway, so I definitely think it’s not shifting into 3rd for some reason.

Is it going into 3rd gear though? You can shift manually from 2 to 3 and feel the shift. If you were in the trans the fluid gotta be the right level. If your vacuum modulator was not working you won't get second until 35 plus mph.

 

[JoeJoe_91]

Personally I'd unhook the vacuum line down at the modulator while it's running and verify a vacuum signal .

I did that a few days ago, I put it to my finger and it did have suction.

 

[JoeJoe_91]

Is it going into 3rd gear though? You can shift manually from 2 to 3 and feel the shift. If you were in the trans the fluid gotta be the right level. If your vacuum modulator was not working you won't get second until 35 plus mph.

It’s hard to tell, I’ll test it tomorrow when I get the filter and pay closer attention. I’ve shifted from D to 2nd going around 40 mph , the engine acted crazy so maybe that was a sign that it was in 3rd. The fluid was a little low, but it was still above the add line. It’s a new adjustable modulator, but I don’t think that’s the problem.

 

[serpico760]

I’ve had this CUCV M1009 for a few years now, and it’s ran at Highway Speeds (65-70) with no problem until recently. It wont’t go past 55 mph even when I’m going down a huge hill, and it revs really high every minute or so while driving it at 55. It also seems to shake a lil bit when I’m at 55mph, it never did that before all this started.

Replaced:
Transmission Filter
Kick Down Solenoid
Vacuum Modulator - Old one was STOCK (I’ve tried adjusting )

Checked:
I cleaned my CDR Valve (Soaked in gas overnight)
STOCK Vacuum Lines (I’m gonna replace soon)
I shifted the Vacuum Regulator forward a 1/4”

Any ideas as to what I should check, clean, or replace? Any and all help would be much appreciated, I’ve never had to take it to the shop for any of the work I’ve done to it. I’m not an expert on the 6.2 Diesel, but I’ve learned a lot the past few years from this website alone. I’ve tried everything I can think of, I came here to ask the experts before I destroy the truck since it’s my daily driver.
View attachment 898476View attachment 898477

Won't go over 55 and revs high while driving...
Sounds like every unmodified FMTV, but I digress!

 

[JoeJoe_91]

If it's down on power and surging start with the fuel filter.

You were right on the money. I put the new filters in and she opened right back up to highway speeds with no issue. I just have to adjust my regulator and modulator back to how it was, the shifts were funky. Thanks for yours and everyone’s help, I’ll know to change that every couple of months to avoid this happening again.