Hello all, I am glad i found this site out, i have read through 12 pages of topics and found lot's of great info. I have a little problem that i am hoping someone here can help me with. I got a 95 1500 2x4, I put a 3 in Body lift on it with 305/70/16's. The engine was running fine but being this was being used as my wifes primary vehicle we decided to get the engine overhauled. We went to a great machine shop and he rebuild the engine for us new cam, rockers, 1 new head (hairline crack in it.), we had some problems with the rebuild due to bad lifters from the supplier 2 set's. Got engine working good and then had a tranny line bust on me while driving on the road, had the tranny done he rebuild it also put in new plantary gears and overdrive gear. since that time i have noticed that while driving down the road with or with out the cruise set i cannot maintain speed over about 64 or so. The truck loses speed and then i have to speed back up or cruise does it but happens very often. I in a mile of driving it shifts 6 or 7 times to maintain the speed or catch back up to the set speed. I took the truck back to the tranny guy and he ran it on a 50 mile trip with guages hooked up to the truck in lot's of places. The fuel pressure never dropped, the tranny was running and shifting fine but he was at a lose as to why it would lose speed over 64 or so while trying to maintain it. If anyone can help please do if you need more info i will supply all i can.

Thanks ahead of time.

Evixor

 

Could have quite a it to do with the fact your new tie size is almost two inches bigger than stock. I would say if your already dropping all this cash on the motor and tranny and all that, you can probably afford a new set of gears in the back too. Anyone else got another idea? That one strikes me as immediately obvious.

 

Might want to check the vaccuum line going the the cruise can. I think it is under the battery. A couple of threads have mentioned it as an issue. Also if the RPM's are under 1500-1700 the motor has little umph in OD and will loose speed until the trans kicks in another gear.

 

Ok cool my gearing is at 4.88 in the rear end and all is fine sorry i forget to say that, but Chopper 1's thing could be it. i run about 1300 to 1500 at 65 since the overhaul of everything so that is a strong possibility of what is going on. I guess i cannot also do anything about it. ok thanks for all ya'll help.

Evixor

 

Are you sure about your gear ratio. It seems to be low RPM's for that gear ratio.

EDIT: I'm running 3.55's and my RPM"S are higher on the highway. I do have smaller tires, but your RPM's still seem low for that gear ratio.
What size was the new OD gear put in?

 

forget your cruise... you mentioned that it does it in or out of cruise control...

if you stay in 3rd what happens? I'm thinking the torque converter might be slipping... if you can have the tranny shop disconnect the lockup solenoid and take it for a spin to see if it still does it, that might help eliminate that as a possible problem. what rpms are you turning? could your motor just be running out of air/gas? I'd imagine with 4.88's & 35's you should be in the mid 2000's for rpms while in od...

 

I have to agree with these about the RPM and gear ratio. I have 4.56 and at 70 I'm turning around 2000rpm's with 35's. 75mph 2300rpm's. Try running without the OD and see how it goes.

 

The RPM are off it is closer to 2000 then 1200 i was off quite a bit for some reason i put rpm of 55 not 65, sorry but with overdrive off i maintain the speed fine. I was told by the Tranny person that he put in Ram Diesel overdrive gears and plantary gears. I had the tranny guy take it for a drive as stated above and he had lines and wires hooked up all over it and said all looked good he was blaming the engine builder saying it had to be something with the engine rebuild i just had done. I tried going back a forth between the 2 of them for a month or so, and i finally gave up and then i found this site and said maybe someone here knows.

Evixor

 

with the fact that you have 4.88's i'd still lean towards the tranny. if your motors going to have a problem, you'll see it in all gears, but more so towards the top, 3rd, 4th gears. since you say it's good in 3rd, it has to be in the tranny/torque converter. I still say rig it so the TC wont lock and see how it does. if it's the same then at least you know the TC is not slipping.

 

i have a 318, stock tranny, and engine, and gears.
i can run in OD at about 60. but yeah, if i shift out of OD, i have power, when i go to get back into OD ,i will lose power no matter what.
this is all on FLAT interstate.... haha, i can't get up ANY hills as of right now.
4.56 gears are on the way... we'll see how they do.

if u are running 4.88's.... you shold be ROLLING and no power issues... Engine Problem i am guessing.... could be either reallly.[:@]