[MisterTea]

Hey everyone,
I am new to the forum and I just purchased a used wells cargo trailer. My van is a 2001 GMC Savana 3500 LWB cargo van with the 5.7L Vortec and I believe a 4 speed transmission. The original owner states that the trailer has a gvw of around 7500 pounds and towed it with his Ford Econoline 350. Well the other day I loaded her up with about 3000 lbs and could barely get the vehicle speed over 35 MPH on the highway and pulling hills felt like I was going to blow out the tranny (engine roaring and barely gaining speed). The van was pretty much empty except for me, a passenger and a tool box. I figure the curb weight of the trailer is 2500 and together with the 3k load was around 5500 lbs gross weight.

I have hauled a few HEAVY loads in the van, upward of 2500 lbs, and that feels very heavy. Normally I move around 1000 lbs on average.

Right now I am under the assumption my van simply can't handle the trailer and I have to buy another van that is spec'd for towing. And buying a new or even used van is out of my budget. Is there anything I can do to increase my vans towing capacity? I know the rear ratio might be a problem, I am looking into finding out what my ratio is.

 

[j cat]

the vehicle should tow 6000lbs. with normal sluggish tow effort. now I would look to install a transmission cooler. also I would only tow in 3rd gear. you have to use 89-93 octane when towing. replace fuel filter/check fuel pressures , new air cleaner . use synthetic oil.

check for a restricted exhaust. could be clogged cat converter.

I used to tow with a 1983 307cu car a 4200lbs boat . towed real good , but I had a huge tranny cooler and with a carb a ram air setup . also a 3 core radiator. never had a problem 380,ooo miles sold vehicle. 17yrs of use.

 

[BurbanMan]

the vehicle should tow 6000lbs. with normal sluggish tow effort. now I would look to install a transmission cooler. also I would only tow in 3rd gear. you have to use 89-93 octane when towing. replace fuel filter/check fuel pressures , new air cleaner . use synthetic oil.

check for a restricted exhaust. could be clogged cat converter.

I used to tow with a 1983 307cu car a 4200lbs boat . towed real good , but I had a huge tranny cooler and with a carb a ram air setup . also a 3 core radiator. never had a problem 380,ooo miles sold vehicle. 17yrs of use.

I don't see how changing to synthetic oil is going to increase his performance. The only thing that will do is increase oil life

 

[RayVoy]

felt like I was going to blow out the tranny (engine roaring and barely gaining speed)..

Sounds like the transmission is slipping, or stuck in one of the lower gears.

 

[j cat]

synthetic oil transfers heat better also less friction help reduce engine temp.

what could be happening which I did not mention is detonation. this even if small will reduce the timing. this will occur with the higher engine/oil temps when towing in the warm weather.

when I change those items with the car towing my 4200 lbs boat I was amazed at how reducing the engine temp caused the engine to produce the rated HP. a overly heated engine cannot do it.

 

[RayVoy]

I know the rear ratio might be a problem, I am looking into finding out what my ratio is.

Here are the common gear ratios, currently being used by GM, for the trucks (although, the 3500 trucks might some I didn't list):
GV3 = 3.08
GU5 = 3.23
GU6 = 3.42
GT4 = 3.73
GT5 = 4.10

Check the build codes on the glove box sticker. One of the above should be listed.

EDIT: I just googled some numbers. The 350 engine with a 3.23 axle can tow 6,400 lbs. The same truck with a 3.42 axle can tow 7,900 lbs.

felt like I was going to blow out the tranny (engine roaring and barely gaining speed)..

Does the truck have a tachometer in the dash? If it does, give us the rpms when doing this hill climb and the engine is roaring.

The other thing that needs to be checked, is the rolling resistance of the trailer.
Do you have sufficient air in the tires?
Do you have a brake dragging?
Are the wheel bearings free?

It should push the truck down hills (if truck is in DRIVE)

 

[MisterTea]

Thanks for the tips everyone. I will give the van a tune up, it is due for one. I also notice that the van runs hotter and its much hotter under the hood especially with the AC cranked and towing.

One thing I forgot to mention was once I towed a way too heavy load, estimated 11-12,000 pounds a few years ago moving a forklift on an equipment trailer. Towed it 40 miles and was able to get it to 50 on the highway. It was heavy and I did a tune up not too long before.

 

[donl]

My parents bought a new 1985 customized Chevy 20 van with the 305 and it was a huge gas burner and just gutless. Too much weight and not enough motor. It didn't have enough power to pull a stiff dick out of a lard bucket.

 

[j cat]

My parents bought a new 1985 customized Chevy 20 van with the 305 and it was a huge gas burner and just gutless. Too much weight and not enough motor. It didn't have enough power to pull a stiff dick out of a lard bucket.

well at least this guy does not have that 85 chevy 20 van like your parents. the 305 cu is a cheap GM motor. Poorly or I should say cheaply designed. poor MPG and power. but GM made money selling those vehicles.

I still have the 84 camaro 305 cu carb. 12 MPG max.

 

[4by44ever]

i'm thinking:transmission trouble,watch out that you don't blow it up.
I did,last month

 

[SolWav]

Have to agree something is out of sorts you should have plenty of power too pull that trailer.

 

[SolWav]

Just read your thread, you certainly have a problem. The 3500 I have has towed 9000+lbs and maintaining 65mph is not a problem. Not sure to recommend too begin looking but you have a malfunction somewhere. Best of luck.

 

[tsbrewers]

I agree, mine is an '06 3500 and it will pull most things very well. It isn't set up for towing either, I had to add a cooler, 3.73 rear end, trailer wiring, etc. I have a relatively heavy boat and I don't know it's there. Barely affects my mileage too. I average around 14mpg typically and get about 13-13.5 with the boat.