hard downshifting

[gear_grinder]

hi, i have a v8 sploder with the 4r70w. when slowing down it seems that when the tranny downshifts into 1st gear it slams in to it fairly harder than any of the other gears. its not alarmingly hard but you can feel it, it might just be a qwerik of the tranny. the fluid looks a tad dark but not bad and doesnt smell, but i am going to have it changed anywho. any ideas?

 

[BrooklynBay]

Does the fluid look like any of the colors in this chart:

When was the last time you replaced the fluid, and the filter? What kind of fluid is in there now? How many miles do you have?

 

[gear_grinder]

the truck has 132,x.. miles on it, it shifts while accelirating fine. i dont know when it was changed because i bought it salvage and fixed it. The fluid was a little dark but it didnt seem or smell burnt. I went to a local junkyard today and got a tranny cooler off of a 1st gen sploder and routed that inline with the stocker so now i have dual tranny coolers (cheap insurance and protection).

the color looks exactly inbetween the "new fluid" and "still not bad" colors.

http://www.explorerforum.com/photopost/data/503/trannyfluid.jpg

 

[Glacier991]

Hmmm... a harsh 2-1 in the 4R70W when every other downshift is ok does not bear good tidings. In a general sense, this implicates one or the other of the one way clutches - intermediate (my guess) or low. I'd change the fluid and filter and live with it as long as I can.

 

[gear_grinder]

let me rediscribe it, it feels like the tranny shifts 2-1 a LITTLE hard SOME TIMES, but it "engine brakes" after in first gear like i manualy put it in first gear.

 

[Glacier991]

Engine braking as you describe in regular 1st gear (not manual 1st) implicates the low one way clutch. It sounds like it is not overrunning as it should.

The low one way clutch is also known as the "planetary clutch". It is shown in this installment of the 4R70W rebuild diary. It is a roller clutch with accordian springs as shown here:

http://www.explorerforum.com/forums/showthread.php?t=157487

 

[gear_grinder]

i also forgot to mention that my speedometer is aprox 10mph fast (reads 65 at 55) because of my t-case swap (differnt tail shaft gears I guess). could this mess with the tranny?

 

[35Remmy]

GEAR, my 99 Ranger does this occasionally, and it's because of worn driveshaft splines.

Yes, sometimes when coming to a stop, it will "bump" as I'm almost to a complete stop.

Typically, greasing it fixes it, but not always.

My dad AND my brother both have the same vehicles (well, one's a Mazda, so same vehicle) and they've BOTH had this issue.

Replacing the driveshaft fixed it, but replacing ONLY after greasing it no longer helped.

It will ALSO jerk or bump when taking off from a complete stop...probably 50% of the time. I haven't done anything about it because I know it's not a major problem.

If you want mechanical perfection you don't buy American vehicles. I'm a PROUD as hell vet, but that's the inconvenient, uncomfortable truth.

 

[gear_grinder]

ok, i'll check the splines and apply grease and see if it helps.

 

[35Remmy]

GEAR...I CAN'T guarantee anything, and I'd hate to have you do the work and see no results, but it's worth the try.

When the driveshaft slides out of the transfer case, that splined end is what is supposed to be packed full of grease.

 

[gear_grinder]

it wont be that much work if it doesnt work anyway, i just got done with my 4406 swap a little while ago so everything should come back apart fairly easily.

I set up an apointment to have the fluid flushed and changed tomarow and bought a bottle of "Tranny Honny" and asked my local tranny expert (40yrs+ rebuilding them) and he said that some of them eat the seals in the tranny. does anyone have any experience with this stuff?

 

[Pete70SS]

Gear grinder, Let me know if greasing the driveshaft splines worked or not as I have the same problem on my 2004 XLT. I replaced the right front drive bearing assembly & I noticed the "bump" started about then. It is a sealed bearing so I don't know where I would grease it.