2nd Gen Non-Engine/Transmission '97 3500 Extremely Poor Mileage

[Max Wedge]

A friend of mine has a '97 3500 4x4 towing a 7500 lb loaded enclosed car trailer. Auto Trans-3. 54 Gear-235 Tires. Only mods are: BHAF--#5 fuel plate. There are NO guages, so boost & EGT's are not available. Towing is on major Interstate Highways with small rolling hills ie... usually no more that 4% grades with no more than 1 mile in length at leagal speed limits of 65-70 mph. MPG is 8. 5



Truck has 170,000 miles and transmission is a Mopar exchange with 2 years worth of service. Any ideas would be deeply appreciated, as he sold his 454 Chevy dually to get Dodge/Cummins--chevy got 5 mpg with more get-up-and-go.



Help!



Max

 

[JDougherty]

not an expert but does he still have the catalytic converter on. how about the fuel filter... when was that changed.

 

[Max Wedge]

Fuel Filter Changed 11/03 and yes, he still has catalytic converter on.



Thanks for reply.



Max

 

[JDougherty]

i have heard they will clog up around 75k which could lead to poor performance... to the point where dodge makes a test pipe for this

 

[crabman]

Part Number

MW,

The Dodge catalytic converter part number is:

P52019170AB



crabman

 

[Max Wedge]

Was talking to him on the phone about his trip Saturday and he has noticed that the best performance is achieved by holding the truck at about 3/4 throttle--any more throttle and the truck seems to nose-over (lose performance). Make any since?



Thanks so much for all the replys!



Max

 

[ToolManTimTaylor]

#5 Plate and no guages? Not radical but even so it's a good idea. Granted the 3:54's and 235's don't really help in any situation for towing large AND getting mileage, but there is an issue there with performance dying off after 3/4 throttle. Sounds like either a boost leak , or an intake restriction , or exhaust restriction which is not allowing complete burn at WOT.

 

[crabman]

Clogged

MW,

Yes, it makes sense.

The c/c is holding up the amount of exhaust gases that can pass through the exhaust system. Did you ever put a potato in a exhaust pipe? Does the same thing.

Remove the c/c and he will pick up better MPG's and more RPM's.

crabman

 

[willyslover]

sounds like he has no clue about . . tune up and basic mods... better tell him to spend $35. 00

 

[wcjp]

Being a manual guy I can't say for sure. Doesn't the auto benefit from a 3k GSK? Also, when testing the cat try upgrading to a full 4" turbo back.

 

[Max Wedge]

Originally posted by willyslover

sounds like he has no clue about . . tune up and basic mods... better tell him to spend $35. 00

willyslover;



If you can't contribute something of value, STAY OUT OF MY THREAD! He is allready a member of this Great Organization, just not active on Web. With comments like this its a wonder "Most" people are members!



I am sure am glad 99. 9% of the TDR population has common sence.



Max

 

[CATCRACKER]

max,



willyslover is right if you are going to mod a truck it should be done the right way. if he is complaining about the cummins and how his 454 will kill it pulling tell him to sell his truck. why do i say that b/c the majority from this board could take his truck get about 350hp easy and pick up the mpg..... tell him to do it the right way just like willyslover is talking about. tell him to come off some $$ more than $35. if he wants to pull something that heavy and get good fuel mpg and get up to speed fast he better reach in his pocket. oh yea use the search mode on this board you can get good answers about poor fuel mpg doing that.



1. brake dragging

2. boost issue (holes in intercooler, bad hose, loose boost horn, etc. )

3. clean sensors



there are many more

 

[Max Wedge]

He doesn’t want 350 HP. He purchased this truck based on the fact that mileage would be a great upgrade i. e. … 11 to 12 mpg compared to his old 5 mpg. And this is 8 mpg towing has been going on for a long time. Boost is around 25 lbs—checked last month, brakes are less than 6 months old—front—no signs of pulling left or right.



As far as his old Chevy is concerned, who said he was complaining—he was just stating a fact that mileage is no where near what the rest of us (8 in all) are getting. That is why I put the post out there.



I guess you can’t ask on honest question here anymore without getting hammered over BOMBing the crap out your truck. He knows that gauges are needed, but at his current limit of modifications should not be necessary.



10 to 11 mpg should be a given, not something to be strived for. Yesterday I was pleased with responses and showed him on the net, now I will be embarrassed to have him see where this has gone.



We will be removing the Catalytic Converter to see if that helps out. We are all not out to get MEGA Power to brag about, just a nice well rounded truck to suit our needs.



Max

 

[willyslover]

MaxWedge. . first off [on edit . . words removed on request by moderator] I in no way was flaming you or the fellow you posted for. .



now with that said... I said have him spend the $$ cause there is much more to learn than a short thread will ever allow. . and membership here will provide that info. . no quick answers will get the info into his knowledge base... if he is a member then he needs to become active and not look for the short cuts. . as there is NO SHORT CUT TO KNOWLEDGE and this group will gladly help anyone out even folks that assume flaming when none is there !

 

[Joe G.]

If he is towing with a #5 plate and no EGT gauge he is asking for trouble. Melted piston or torn up transmission are likely.



There is a cat test pipe that exactly replaces the cat. Costs a little over $40 I think. I have the part number around here somewhere. If I can find it I will post it. A forum search should find it if I can't.



BTW. The truck he has is almost the worse possible combination for milage.

 

[Joe G.]

The part number for the Catalytic Converter Test Pipe is #52019170AB.

 

[ToolManTimTaylor]

Originally posted by ToolManTimTaylor

#5 Plate and no guages? Granted the 3:54's and 235's don't really help in any situation for towing large AND getting mileage

Originally posted by Joe G.

If he is towing with a #5 plate and no EGT gauge he is asking for trouble.



The truck he has is almost the worse possible combination for milage.

C'mon guys let's chill out with flames and Name "Associations"



Seccond as I pointed out above is that the common theme here is he has a couple strikes against him getting good mileage whilst towing. The 3:54 ratio really is a bummer gear to try to tow with (Especialy at 7K large) as the cummins really should not be lugged. (Lugging meaning anything under a general 1400 rpm) and that particular ratio screams lugging. So with the motor lugging he is feeding it more throttle which is dumping more fuel which is in a sense putting the fire out and it simply cascades from there.



The 235's are adding to his dismay as the 97's came with 215's. So the tire size being upped also is increasing (Lowering the ratio) of the gears effect. The bummer is that he COULD do a gear swap to a more aclimated 4:10 ratio (Ideal towing mileage , performance and all around gear) however it wil cost him some big bucks to do so. He also could rack down on the plate so he is not overfueling so badly as well. He has alot of fuel going into the motor with no other aids to get it out (I. E 4" exhaust , larger housing etc) but anything more than that #5 plate and that stock trans may just send him a post card from it's vacation spot.



Does he have any mods that maybee you could have not listed??

 

[GeneA]

Maybe I missed something here but with the 235's he is doing more miles than his odo is showing and without compensating for that he may be getting the mileage he wants.

 

[I-6DZL]

i may have missed something here but... a 235 tire and 3. 54 gear ratio should run around 1800 to 1900 rpm at around 70 mph.

235 vs a 215 tire will not affect the mileage nor the speedo that much 2 maybe 3 mph.



Let me know if i got the "WHOLE" story or if i missed anything



I-6DZL

 

[Joe G.]

Tim,



I did not post that as a flame at all. It's an observation of the situation as I see it. A 3500 4X4 with auto is going to get poor milage. His seems kind of low even for that truck. High EGT is certainly a concern with a #5 plate when towing.



His truck is an automatic so it does not have the 215 pump.



I tow a 32' TT that weighs about 8K loaded. My milage is about 13 (sometimes 14, sometimes 12) with 3. 54 gears. Depends on hills and wind. So his milage should be better than he is getting. Maybe the cat is plugged. Maybe his timing has slipped. Maybe his overflow valve is shot so the fuel pressure is too low to make any power. Maybe he is lugging it by towing in OD in situations when he should not.