My truck is a 1994 1500 Ram 4x4, It has the 5.2L V8. I have put a 3in lift on it with some 35x12.5inch BFG all terrain tires. It also has some small mods like 40 series flow master and k&n. My problem is that after putting the lift and tires on it, while driving down the highway at 65 and having the cruise control set to 65, it wont hold and maintain that speed on a level grade. As soon as I set the cruise it will start to fall below 65 and then down shift to catch back up. It is a pain in the butt to drive this down the high way with all the down shifting every 1mile or so and kills the fuel mileage. I know that its pretty much like driving a lifted box down the road but was curious as to whether someone makes a programmer for my truck that could help with this problem or maybe there was an adjustment that i didnt make and should have. Thanks in advance

-Darin

 

Probably have a small vacuum leak in the line that leads to the cruise servo, or in the servo itself.

Welcome to DF.

 

Thanks for the welcome im happy to be here and wish I would have joined a long time ago. Thanks for the advice I will check it out and let you know if it corrects the problem.

-Darin

 

Its a great place. There is a WEALTH of information here...... (some of it you really won't want to know... but..... better to know, and prepare, than be surprised. )

Given your symptoms, I would take a long hard look at the servo itself. Its under the battery........ so, might have to slightly disassemble the front half of the truck to find it, and actually be able to inspect it.

 

Did the cruise work before the big tires? What gear ratio are you running? On my '94 when I have my 285/75/R16 tires on (3.55 gear ratio) cruise is almost useless, I can barely hold speed on level ground. The motor struggles to turn those tires and the final drive ratio is off so the computer does not know what to do. I suspect the cruise is working properly, its that your truck does not have the torque to hold speed.

Your mileage is getting hurt more from the large tires then downshifting. If you have 35's and stock gears you may want to consider running out of OD all the time as you are damaging your transmission.

 

Well Gerehead8, this is what i originally thought was the problem. That it just couldnt hold speed because of the tires. It didnt do this before i put the tires on. It is running stock gears. If the servo and hoses check out ok, do they make a kit or programmer for the problem that I am having to increase RPM's with out changing out the gears. And ya there is always just not running it in O/D but then its running at 3k RPM. Thanks

-Darin

 

Your truck is to old for a programmer. Only way to increase rpms is to downshift or speed up, your engine rpm and speed are directly connected (auto trannies can cause this to be a little off but it is mostly true). The reason your truck downshifts is because the cruise is pulling the TB open enough trying to get the truck to accelerate that it downshifts.

You can try going faster as your motor makes more torque at the higher rpm.

You should be at about 2500 rpm (maybe a little higher in OD with the torque converter locked up. Try cruising with OD locked out (button) so the trans will lock up in 3rd gear. It is much easier on the tranny.

I have the 5.9L with full exhaust, CAI, fixed plenum, HS 1.7 RR's ect. and my truck doesn't have the torque to hold in cruise with my tires that are smaller than yours.

4.56 gears will solve your problem but cost $$$.

 

hey just wanted to give an update. Traced the vacuum lines coming out of the servo and found one that was unplugged. Cleaned it up, threw it back together and took if for a drive. Works as it should now and holds speed fine. Driving into a stiff wind still makes it down shift but i assume that is do to the torque issue, big tires, and fact that the truck catches a lot of wind. Thanks for the help guys, glad I got it figured out with your assistance.

-darin

 

I have seen them described as a "brick with wheels", so yeah, You are quite accurate in your assessment. Glad to hear ya got it solved.