Tow vehicle question

D

Dan McNally

New member
Ok Brats, help is needed again, can someone on this site offer some help with a tow problem? The long and short of it is, I have a 1995 f250 supercab 4x4 with a 460 as my tow vehicle, the truck has 90,000 miles on it and should be able to handle my 22' dory and a 9 1/2' camper at the same time. The problem is that since I had a new torque converter installed at a tranny shop the truck will hardly pull a grade, I took it back to the shop when I found the problem (shortly out of warranty) and they said every thing works fine. It does to a point, it does not slip, miss or otherwise act up, but it will only go up hill at about 20 miles an hour when loaded. If unloaded and I pull a mountain pass it travels well, but if I drop it into passing gear it shifts and the rpms increase but no increase in speed. Anyone have a suggestion as to the problem, I am not mechanically inclined but would like to be more informed when talking to a repair shop this time.

Thanks, Dan.
 
Dan-

Does your transmission have an electrically activated overdrive that locks up the torque converter past a certain speed? If so, does it have a lock out switch, and can you lock it out presently? Sounds like your torque converter is locked up and doesn't allow any slipping to allow the motor to rev up under heavy loads? (I'm no mechanic, but my best amature guess.)

Roger (Dreamer) knows about all this stuff, having worked in the auto/truck repair industry.

Good Luck.

Joe. :teeth :thup
 
It would seem that something is dramatically wrong with the tranny--and perhaps with the engine. I am driving a 30 foot RV pulling a CD25 (Ford Chassis, and the V10 1999 engine). Total weight is somewhere near 26,000 lbs (which the chassis and running gear is rated for) The lowest speed I see on grades is about 35 mph. I did have the transmission upgraded this year, with a heavier duty torque converter and the ability to lock it. Before it would shift to the next lowest gear--in and out--on steep grades. Now I just put it in gear and it does not down shift, until I manually do the down shift.

Another question is what is the rear end ratio?

I assume that you lock out the overdrive when you are going up hill. Have the transmission expert check for upgrades and for problems with the torque converter. What RPM are you running up the grades? (tachometer?) Do you have a vacuum guage? Both of these are helpful when pulling heavy loads with a gas engine.

With that rig you should be able to go much faster up hills...
 
Bob,
I do not recall rpms exactly but they did not seem to be out of line, I do have a feel for the type of performance that should be standard, because I have always had a truck and pulled a boat and camper for the better part thirty years. The strange part of this issue is that the only time it is really noticeable is when I have the boat and camper on the truck together and I am pulling a steep grade. On level ground or getting up to freeway speeds every thing seems normal.
I will just take it to a different mechanic and have them look at it and give me their opinion I guess. It just is frustrating to take it reputable place ( Lee Miles) and be left holding the bag so to speak.

Dan.
 
Dan, been there done that...
This is a long shot; it could be your gas cap; try loosing it and see if your engine pulls better. If this solves your problem its because you gas cap breather valve is shot, replace the cap the tank is pulling a vacuum.
If this isn’t the problem then look at the fuel pump, the symptoms you described could vary well be a faulty fuel pump.
These are the two areas I’d look at first before spending the $ having a shop check it out; fuel caps and fuel pumps are relatively cheep.
 
Are you sure the change in performance happened exactly when you had the torque converter changed? No other changes? Had you recently been able to handle the same load with better performance just before the new torque converter? It sounds more like a tired engine than a transmission issue I'd think. If it's slippage, I'd think you'd notice the engine rpm climbing while the speed drops. If not, then it seems the engine just isn't making enough power.

The overdrive switch is probably the same idea as I have on my 2000 Silverado. The overdrive is the fourth gear of the transmission. First three are underdrive ratios, fourth is overdrive. The lockout switch keeps it from shifting into and out of fourth all the time when you're driving on a fairly level stretch and the load keeps changing slightly with small road grade and wind changes. The transmission would keep shifting in and out of overdrive, which is annoying and causes needless wear, so they give you the switch to stop that from happening.

Once you get down to the speeds where you're only using the first through third gears anyway, the switch has no effect.

I suppose something could be tight or dragging somewhere and wasting power that way, but it seems like you'd notice that in performance or ridiculous gas mileage in general.

It just sounds like the engine doesn't make top end power any more. How about a compression check? Or maybe try a zero to sixty run and see how the time compares to some information you can find somewhere from a similar truck?

Another thought, just in case: Does this truck have stock tires and gearing, or has it got extra large diameter tires? That would effectively change your gear ratios and could make things worse on tough grades.

You could also weigh your rig and the boat. You might have it loaded a lot more than you think.

I hope some of this might help or lead you to some different investigations at least. I had probably your same engine and transmission in a 93 RV and it made a LOT of power. I towed boats with it and it did well, but I don't remember details that would help you compare.

Jeff
 
Brats,
Just to give a little history regarding the torque converter issue, I had a seal problem with the original one that came with the truck so I had it replaced, it seemed to be working fine until I put a load on it with both the boat and camper. There is no problem with drag from a brake being hung up, or with the engine being worn out. I have driven the same roads and pulled the same grades with the same equipment and scooted up the grades at any speed I wanted to go, so the problem seems to be the new torque converter.
Thanks for the input, I will let you know when I have the problem resolved and what the solution is.
Dan.
 
A few thoughts here.

First it could be a fuel delivery problem as Jay states. IE: Gas Cap, Fuel Filter, Fuel Pump.

It could also be a slightly plugged Catalytic Converter. This will manifest itself first during very heavy loads just as you are describing. Eventually getting to the point where your truck simply won't get out of its own way. Try putting a vacuum gauge on the truck while pulling a load. When you are open the throttle the vacuum should drop to near 0 and then build back up while you hold the throttle at a steady position. If it instead builds for a second and then slowly drops you have a plugged exhuast system. Converters typically go out around 100K miles so this would be my first guess.

Finally, are you sure they gave you the correct converter? And did they rebuild your tranny at the same time? Its possible that you ended up with a different set of gears thus losing some of your mid range torque. This will be extremely hard to prove though!
 
Gary,
I just went for a ride with the owner of the shop that did the work and as you stated the truck will hardly get out of it own way. He stated that it was not the transmission or the torque converter but he felt it was most likely the catalytic converter as the truck performs well till you hit 3,000 rpms then it just goes flat, it does this even when it is unloaded. The shop says they can test the converter by disconnecting the exhaust before the converter and test drive it to see if performance is increased.

Dan.
 
I had a cat converter blockage problem in my 96 1500 Ram. Popped the hood after a long pull up a canyon and the exhaust manifolds were cherry red! Scared the bejesus out of me. Put Flowmasters and a low-restriction CC on the thing and it helped a lot.

Warren
 
Dan,

The E4OD trans in your truck has an electric clutch that locks up the torque converter when in cruise mode and little demand on the engines torque. There are lots of malfunctions in that torque converter that could cause your symptoms. If it locks up prematurely, you lose all the advantage of multiplying torque like it's designed to do.

That being said, the Catalytic Converter on those trucks are prone to failure. They plug up and choke off power at higher RPMs. If yours hasn't had one yet, it's a good bet it's due for a replacement. Sorry, it's one of the biggest and most expensive ones out there. They're usually over 1 MMU (Marine Monetary Unit= $ 1000).

In good condition, the 92-97 F-250, 460 is good to tow 8500# with ease. I worked for a Ford Dealer and we saw these problems all the time. They might be the best ones to diagnose the problem. Labor rates are higher, but they know the vehicles.

Best of luck,
 
It is likely the cat.....My 78 f250 with a 460 will tow from Anchorage to Seward over the passes as fast as the law (65 mph) will allow without a problem with my cd 22 behind it. I really have a hard time believing that the tranny is causing this type of problem.
 
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