1990 K3500 454 Turbo 400 problem

krandall · 10-04-2006, 07:55 AM

I have a 1990 K3500 ton truck 4X4 with the 454 and turbo 400. Transmission worked flawlessly until one day it would not upshift unless rpms were really high. Found a hole in the modulator, replaced it , solved the problem. But now when I go down a hill the transmission will not help me slow down and kind of acts like its freewheeling. If I downshift into 2nd while coasting down a hill the transmission will not help slow it down .Any ideas ?

ChevYvehc · 10-04-2006, 10:49 AM

Hit the brakes?

mudseeker · 10-04-2006, 05:38 PM

that was funny.^^ but yeah why put the added stress on the tranny when you got a brake pedal.

krandall · 10-04-2006, 06:37 PM

I thought someone on this forum might know something about transmissions. Maybe not.

ChevYvehc · 10-04-2006, 07:34 PM

Quote:

Originally Posted by mudseeker

that was funny.^^ but yeah why put the added stress on the tranny when you got a brake pedal.

I dont know, thats the first thing that comes to mind when im going down a hill and picking up speed

ChevYvehc · 10-04-2006, 07:35 PM

Quote:

Originally Posted by krandall

I thought someone on this forum might know something about transmissions. Maybe not.

Give it time, some one will give a seriouse answer.

mrjohnwayne · 10-04-2006, 08:40 PM

Quote:

Originally Posted by mudseeker

that was funny.^^ but yeah why put the added stress on the tranny when you got a brake pedal.

That's were I disagree. Why put added stress on the brakes when you have a transmission. The tranny will help slow you down believe it or not.

As for the not downshifting i'm leaning towards the modulator getting stuck. You might try to take it back out and make sure there is no trash in it.

bobcat5544 · 10-04-2006, 11:36 PM

Quote:

Originally Posted by krandall

I have a 1990 K3500 ton truck 4X4 with the 454 and turbo 400. Transmission worked flawlessly until one day it would not upshift unless rpms were really high. Found a hole in the modulator, replaced it , solved the problem. But now when I go down a hill the transmission will not help me slow down and kind of acts like its freewheeling. If I downshift into 2nd while coasting down a hill the transmission will not help slow it down .Any ideas ?

The problem with your trans is the one way clutch or sprag.

If you are looking for better assistance try going to www.gm-trucks.com. You can post questions on there just like here and get answers from GM tech like my self.

krandall · 10-06-2006, 06:31 AM

Thanks for the input.

10-04-2006, 07:55 AM	#1
krandall Junior Member Join Date: Oct 2006 Posts: 3	1990 K3500 454 Turbo 400 problem I have a 1990 K3500 ton truck 4X4 with the 454 and turbo 400. Transmission worked flawlessly until one day it would not upshift unless rpms were really high. Found a hole in the modulator, replaced it , solved the problem. But now when I go down a hill the transmission will not help me slow down and kind of acts like its freewheeling. If I downshift into 2nd while coasting down a hill the transmission will not help slow it down .Any ideas ?

10-04-2006, 05:38 PM	#3
mudseeker Senior Moderator Join Date: Feb 2006 Location: michigan Posts: 6,375	that was funny.^^ but yeah why put the added stress on the tranny when you got a brake pedal. __________________ i'd rather be hunting

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10-04-2006, 10:49 AM	#2
ChevYvehc Full Member Join Date: Aug 2006 Posts: 44	Hit the brakes?

10-04-2006, 06:37 PM	#4
krandall Junior Member Join Date: Oct 2006 Posts: 3	I thought someone on this forum might know something about transmissions. Maybe not.

10-06-2006, 06:31 AM	#9
krandall Junior Member Join Date: Oct 2006 Posts: 3	Thanks for the input.