TF727 Questions.

[Cummins4Life]

I'm looking at a 90 W250 auto and i'm assuming that it has the 3spd auto. I havent had a chance to drive it yet but I was curious as to what the rpms would the engine be turning at 55-60mph with 3. 07 gears and 32" tall tires? Also it has 106K on it, how many miles do these transmissions last before they are commonly rebuilt?



Thanks

Zach.

 

[BushWakr - RIP]

I can't answer the speed/rpm question for you personally, but there are other here who can give you chapter and verse on that one...

The things that you should keep in mind are, of course, the speed limitations which you can improve a bit by raising your governed speed from stock (2450 RPM) to near 3000 RPM.

That will help, but you'll still be running wide open or close to it if you want to really push it.

Next is the fact that the early trucks had no intercooler and they also had larger injector holders. This has created a weakness in the head which can lead to cracking.

The area between the valve seats is particularly prone to this problem, especially if you run the truck hard and hot... .

If you use good sense, keep your temps in check and don't crank your timing too high you should be ok.



pb...

 

[bgilbert]

Zach, if its not super cheap, keep looking. Intercooled be the way to go. I bet the 727 in it, has already been rebuilt once, and probly rebuilt to gasser specs. Also you will find yourself only running 55-60mph all the time on the highway, cause the ol cummins will be roaring, you'll be wondering where that 4th or 5th gear is. . I'm used to the 89 with its 5 speed and I have an idea of road speed vs. gear vs. engine roar. Then I jump into the 91 with 3sp auto and once my trained ear hears the particular rpm that I'm used to hearing in the 5 speed, I say ok must be hammerdown near wide open 65+ etc, not, only about 55-60mph with the 3 speed direct. It nice for city stop and go, but not for highway trips, JMO. Like I said if its being given away cheap, ya can;t beat a good running dodge cummins for cheap$$. .

 

[dpuckett]

3. 07s with no OD will net you a final drive real close to 4. 10s with an OD (. 77 for manual; . 69 for auto). The low miles concern me- lots of time sitting, seals hardening, acid from the engine oil doing its thing, as you KNOW the change intervals have gone over a bit. Plus, the Dana 71 3. 07s are an animal all to their own- Dodge only parts IF you can find them. So make sure it is in good shape, and wont need any work for another 400K.



Pastor, what years was the governor set at 2450? The FSM I have (1990) calls for a minimum no load RPM of 28xx; max of 2950 or so. I do agree the governor needs tuning. Before I reset mine, I coudl only get 60MPH out of it in 4th; now I go 68. I just never have had one set that slow, and most of them have been near stock, at least when I first got them. (never had a tach, but I am proficient with a calculator, and can figure road speed vs tire size vs RPM)



I can personally attest to the cracks in the head from a hot head- mine is cracked between each injector bore and intake valve seat. Head gasket was letting a pinhole amount of water through. I am still running it, though (new HG of course). Seems to be ok, though I do need to call the good Pastor and see how much he gets for a ported replacement. INtercooled is the way to go, but not necessarily for the reasons you might first think of.



Mom's transmission is closing in on 250K, and spent 175K pulling trailers of one kind or another. It could use some work ,namely a tighter converter, but it still goes down the road. If you live back east or in the midwest, where the speed limit is 55, you will be ok. If you can go 70+ pass on it, unless the price is right. Check it out like you would any other vehicle. Make sure the transmission fluid is red or pink, it shifts well, TC isnt too sloppy loose, etc, etc.



Daniel

 

[BushWakr - RIP]

Daniel, I guess technically the governed speed is higher than 2450 but I've found that the defuel is about there, and the value of the RPM above that point is almost useless... .

Most of the trucks I've tinkered with would defuel at about 2400-2450 and the max RPM was about 2600.

Still, we can make these things pull hard all the way to 3000 RPM as most of us tinkering types know, but the lack of OD is really a shortcoming that I'd be very leary of personally... . even going to the extent of getting a later model trans or a GV overdrive would be better than just the basic 3 speed.

I guess "they" thought the 3:07's were an answer to 3 gear only issue. .

I'd really like to see a 518 with 3:07's myself. I think that would be a killer combo for us.



JMO... .



pb...