6BT power (or lack of thereof)

[ezcurra]

Hello,

I just bought a 1990 W350 with the 6BT. It runs fine, but it seems very underpowered to me, even when empty. The person who sold it to me said it maxes out at 70-72MPH on the highway. Any simple things I can check?



Also, what is the axle gearing (it's a 4x4), 4. 10's?



Thanks,

Mikel

 

[DBF]

Go to the dealer with the VIN in hand.



Ask him to run the Vehicle Information Plus Summary Report & give it to you. It will show all the items installed on it at the factory, right down to paint colors.



Regards, DBF

 

[CSchafer]

Is it an auto or stick?

 

[sdstriper]

Define power

Hey, No offense intended here. But high speed capability or lack thereof has nothing to do with lack of power. You have a heavy 4x4 not a Corvette. My 2wd truck is turned up some, has 3. 07 gearing and taller than stock tires and still will not go way fast on the top end. I don't care if it does either (go fast, high speed). What I do care about is power in terms of grunt, to pull more than I legally should, pass people with ease while pulling said load and get MPG better than a truck should with that kind of load and "power".



Check the rear axle differential cover, there should be a steel tab on one of the bolts with the rear axle identity and ratio. That is if someone didn't take it off there.

 

[Philip]

From the MPH you listed it sounds like a auto truck. If it is you have 3:07's in it. It also has a 727 auto without overdrive.



You speed sounds a little low on top end. Check to see if you linkage is giving you full throttle.



A fuel filter getting stoped up will kill your top end also.



My truck with 3:07's will top out in the 85 to 88 MPH range in 3rd.

 

[ezcurra]

Hello,

The truck is automatic, with only 150K miles. The fuel filter is new. I know these things are not designed for speed, but 72MPH top speed seems a bit low to me.

Thanks.

Mikel

 

[Philip]

but 72MPH top speed seems a bit low to me

Thats why I said to check your throttle linkage for full travel. Other members has found their linkage out of adjustment before.

 

[KOG]

That's about the speed that my 91. 5 runs in third with 3. 5x gear. But it's a four speed and will run quite a bit faster in fourth.

 

[Philip]

KOG that is why I told him what my truck runs in third. I have the same rear gears. I do have the 518 trans for now. His truck working properly should top out around the same MPH as mine in 3rd. I still think his linkage is worn and not giving full throttle. He didn't say anything about a tach so we don't know the RPM he is running at that speed.

 

[PToombs]

Time for some serious BOMB's! My truck goes 90 in 4th! It is a 5 speed with 3. 54's though.

 

[BPaulsen]

1992, 2WD, auto with overdrive, standard 235/85-16 tires, 180K miles.



A bit low on power right now (still chasing the problem), it'll do about 85 mph on the freeway in full song, although it feels more happy around 70 to 75 mph.

On the bottom of steep, long hills, when I switch off the overdrive, it runs about 65mph in 3rd, but sounds like it's redlining big time (just ordered a tach).

 

[dpuckett]

It is possible to have 3. 54 with a 3spd auto. Neighbor bought one in 89. Said 75 was his top end.



Daniel

 

[Philip]

Daniel when I priced a new W350 C&C in 89 I was told 3:08 was the only gear listed for a auto.

 

[Forrest Nearing]

Hey, No offense intended here. But high speed capability or lack thereof has nothing to do with lack of power. You have a heavy 4x4 not a Corvette. My 2wd truck is turned up some, has 3. 07 gearing and taller than stock tires and still will not go way fast on the top end. I don't care if it does either (go fast, high speed). What I do care about is power in terms of grunt, to pull more than I legally should, pass people with ease while pulling said load and get MPG better than a truck should with that kind of load and "power".



Check the rear axle differential cover, there should be a steel tab on one of the bolts with the rear axle identity and ratio. That is if someone didn't take it off there.

no offense, but if I couldn't go over 80mph, I'd probably drive off a cliff!!! I think my truck probably tops out around 125ish... fastest I've been is 115... 95mph is no problem on TX highways, you won't be the only one!!! outta the way old man! :-laf

 

[DVolk]

6BT power (or lack of thereof )

85 to 90 MPH nothing like bumping the GOVNOR is there

mine likes to cruise at 72 for best mpg not no 85



85 to 90 some bodys going to be wareing enging parts



i only got 2 deisels that will do that my 350 cummins and my tdi

that like high speed running

 

[Forrest Nearing]

85 to 90 MPH nothing like bumping the GOVNOR is there

mine likes to cruise at 72 for best mpg not no 85



85 to 90 some bodys going to be wareing enging parts



i only got 2 deisels that will do that my 350 cummins and my tdi

that like high speed running

there's nothing wrong with riding the governor... it doesn't hurt anything, it's like lifting your foot off the pedal a little, nothing more. as for wearing engine parts? not sure what you're getting at, but the 5. 9 in marine applications will turn 3000rpm all day long... tons of pickup guys have been turning over 3000rpm for years w/ no problem.



I wasn't talking about fuel economy, I was talking about not getting run over! :-laf If you're not doing 85mph on I35, you're getting passed a LOT

 

[JLEONARD]

5. 9 in marine applications will turn 3000rpm all day long

Yea, but those are the guys who rebuild at 1500/2000 hours due to scuffed cyl walls. Marine aplication is like hauling a full load uphill. A boat pushing 3000 rpm at full power doesn't get a nice long hill or a stoplight to cool down. After a while the heat soak takes it's toll.

 

[Forrest Nearing]

5. 9 in marine applications will turn 3000rpm all day long

Yea, but those are the guys who rebuild at 1500/2000 hours due to scuffed cyl walls. Marine aplication is like hauling a full load uphill. A boat pushing 3000 rpm at full power doesn't get a nice long hill or a stoplight to cool down. After a while the heat soak takes it's toll.

well, they have a constant supply of cold water and air/water coolers, so they shouldn't get overly hot, but the point is that RPM doesn't kill these engines (well, not 3000rpm!) heat does...



running down the highway at 2700rpm isn't going to hurt a thing

 

[Budpwr66]

My 92 has run between 110 and 115 since new in OD and right now will hit 74 in 3rd... ... The only time I really lacked power was when the valves needed run, barely made it up the mountain on I-40 over on the NC/Tenn border

 

[ezcurra]

How often do the valves need to be adjusted? This truck has 150K miles. I gotta check the throttle linkage...

Thanks.