Towing revisited OD okay?

[Jeff]

Question at hand...

Is towing in OD okay so long as the transmission isn't constantly shifting?

I have a new (used) diesel 1 ton van and I'm thinking it will be spinning pretty high in the RPM range if I keep it in 3rd at 70mph...

[Jeff]

just replying so I can 'check' to be notified  :P

[GSXR RACER MIKE]

     You shouldn't really have a problem towing in O.D. with that Diesel, as long as your trailer isn't really heavy or has too large of a frontal surface area sticking out beyond your van's profile. Generally a Diesel powered truck will have a somewhat beefy transmission as it is, but make sure you have a trans cooler on it. And like you said, if it's going in and out of O.D. then leave it out during that situation (probably on larger hills or strong head winds). You may also want to look into a performance computer chip that is made for towing (or has multiple setting). Those chips will generally hold in a gear for longer before shifting into the next higher gear.

[Jeff]

Thanks Mike...

Hmmm performance chip...

Any ideas on where?  The van is a 93 GMC Rally van with a 6.2 diesel.  1 ton...

[Eric Kelcher]

What really gets torn up on the diesel transmissions is the torque convertor. The high torque at low RPM Diesel causes issues since most of the TC are designed for cars and have a high stall speed like around 1500rpm what this means is the TC will "slip" at upto 1500 rpm in order to get engine into power band well on diesel the engine is already well into its power band and the slipping causes lots of heat that starts burning up transmission. If you don't have a tach you might think about adding one even if transmission is not hunting 3-4 if it is low on RPM it starts building heat quick. A tranny temp gauge is also a fairly wise investment.  

I have a full complement of guages in my truck and you can watch the stress on engine/transmission if you are lead footed. IF you nail throttle from a stop the turbo temp goes up FAST and tranny temp goes up quick if you roll into throttle and allow rpm to come up then hammer it everything seems to stay alot cooler.

[GSXR RACER MIKE]

Thanks Mike...

Hmmm performance chip...

Any ideas on where?  The van is a 93 GMC Rally van with a 6.2 diesel.  1 ton...

     I personally haven't upgraded mine yet ('02 F250 Diesel) because I may change vehicles this year. There are alot of aftermarket diesel products out there which can be found by looking on a search engine on the internet. I hate to suggest any specific ones due to the fact that I personally have no experience with any Diesel upgrades as of now, but I have heard numerous people say that the chips work great for towing.

     Do you happen to know what trans you have in your van? I would assume it's some variation of a turbo 400, which should be a decent trans. Being a '93 I am not sure if it's an electronically controlled O.D. or not (if so, it's probably a 4L80E). If it's not, then you may need a shift kit installed for towing improvement, instead of the easy chip upgrade.

[Jeff]

Do you happen to know what trans you have in your van? I would assume it's some variation of a turbo 400, which should be a decent trans. Being a '93 I am not sure if it's an electronically controlled O.D. or not (if so, it's probably a 4L80E). If it's not, then you may need a shift kit installed for towing improvement, instead of the easy chip upgrade.

No clue, and don't know where to begin in finding out... ???

[GSXR RACER MIKE]

No clue, and don't know where to begin in finding out... ???

     A turbo 400 based transmission is a large transmission and is easy to identify as compared to a turbo 350 based transmission. Turbo 350 based transmissions are not made for higher demand situations, yet were put in everything from Corvettes to pickup trucks. Turbo 400 based transmissions are put in higher demand situations, my '95 3/4 ton Suburban had a 4L80E transmission (which is a turbo 400 with an electronically controlled O.D.). My brother is a transmission builder and uses a Turbo 400 (non O.D.) in his '68 Camaro, which has over a 1000 Hp and does 9 seconds flat in the 1/4 mile.

     One way to tell if it's a Turbo 400 based trans is to measure to size of the transmission oil pan on the bottom. If you measured that pan I could tell you which trans it is. I would also imagine someone at an autoparts store could check your vehicles I.D. stickers and tell you which it is. Just tell them your looking to put a shift kit in it and they will have to check which one it is (unless there were no trans. options).

[251am]

 Might wanna check the Hypertech website. Not sure about 6.2s, but they might have something for ya.

[Jeff]

Okay, so after a LOT of looking, it is evident that there is no chip for a 93 GMC diesel.

I did find out though that I have a 4L80-E transmission and a 3.73 axle ratio...

[Super Dave]

Your diesel probably isn't as sophisticated as the more current crop of diesels...and it's low on displacement, has no turbo, and has no intercooler.  

Not much you can do to it to make it more powerful without dropping a serious amount of cash.  

3.73's are probably good.  Do you have a tach?  I run my bus with the OD on, but I have 4.10's too.  As you go faster with the diesel with more RPM's out side of the optimum...you'll loose fuel mileage.  You might want to try to find some 6.2 enthusiaist groups that have some ideas for good RPM's and they might have some ideas for mechanically shimming something in the fuel system to make it perform a bit better.

[GSXR RACER MIKE]

     I spoke with my brother (the trans. builder) tonight and he said the 4L80E (Turbo 400 with an electronically controlled O.D.) should be a good trans for that Diesel engine. He did suggest getting a trans. cooler made for that vehicle, if not already equiped, and as Eric mentioned earlier he did suggest getting a trans. temp gauge for it too.

     As far as the torque converter slipping issue he said that is somewhat of a misconception and that it's really a torque converter lock-up issue, not a torque converter stall speed issue. The lock-up is what stops the torque converter from slipping and is not only used in O.D., but also 3rd. Some manufacturers do offer solutions to an inappropriate lock-up time, but this wouldn't normally be a problem. The example he gave was his own car, the 1 peviously mentioned with 1000+ hp and a Turbo 400 non-O.D. transmission. His stall speed is 4500 RPM and has a similar lock-up RPM, yet he drives this car around town during the summer and back and forth to the drag strip which is over 1/2 hour away. The entire time he is driving below his stall speed he is slipping, which is a fluid slip, not a mechanical slip, so no wear is taking place. That trans has been in that car for several years, was in his previous car before that, and has seen more abuse than the average tow vehicle is going to see in a life time of towing. The big difference is the O.D. feature, which is the usual failure point, if something happens at all. Since the O.D. planetary gear assembly is located towards the back of the trans it is susceptible to both heat and lack of lubrication. That is the reason for the good trans. cooler and trans. temp guage. You may also want to make sure your trans. fluid isn't really old and if your changing it you should have the trans flushed and the filter replaced for the 'just to be safe' aspect. Make sure you also keep the trans. fluid to it's proper level with the proper fluid, and you should be just fine. :)

     If you do happen to have any problems or any more questions just send me an E-mail and I may be able to hook you up with the Freinds and Family discount ( ;)) if you need work done. :)