4L80E & TH400 Tech.

[softballnrd27]

Not sure if you covered this or not but what is the best way(right way) to convert from the bolt on yoke to a slip yoke on a 1998 4l80e? I ordered a a slip yoke that fits the trans but it doesn't seem like it allows enough slip.

[clinebarger]

Originally Posted by softballnrd27

Not sure if you covered this or not but what is the best way(right way) to convert from the bolt on yoke to a slip yoke on a 1998 4l80e? I ordered a a slip yoke that fits the trans but it doesn't seem like it allows enough slip.

I have not......

The easiest thing to do is run a short "Counter Bored" Yoke, http://www.sonnax.com/parts/3841-slip-yoke

The "Correct" way & a Must for vehicles with a lot of suspension travel is to machine off the O-ring boss & run a long full spline Yoke.

The "Best" thing to do.....Buy a Core with a Full Splined Output Shaft to start with.

[rickpilgrim]

Clinebager, thanks for all your help on the forum here!

We've been going through 4L80E's like cookies at a bake sale on one of our trucks. Doesn't matter if they are rebuilt by Movarus, Good wrench , local shop or junkyard. I only am given a 90 day warranty on these as it's a snow plow(commercial) truck.
We have no check engine light, nothing shows up on the Verus, I have a pile of 2500 mi or less trans coolers and lines plus three new radiators installed to get any warranty. All of them have good line pressure when installed but in a few miles you notice it take longer to engauge first or reverse but still have clean fluid, another 500 mi or so you start to get soft shifts and some flaring between shifts, new fluid and filter and line pressure is 10-16 psi lower and soon the slipping in 1/2/r is very noticeable and we stop running it.
98 K2500 reg cab long box 5.7 powered truck.
We and dealer think it's an ecm/wiring Janessa problem, do you have any ideas?

[clinebarger]

I would like to tear one of them down to see exactly what's failing, Maybe I can walk you through it???

The change in line pressure has me concerned, Using a DVOM set to AMP scale, Connect one of the leads to the each of the Pressure Control Solenoid wires.

Pin 6 of the Clear connector is the PC High control
Pin 16 of the clear connector is the PC Low control

Use your scanner to monitor the Commanded Amp's......It should match the Actual output read by the DVOM. If it's off (Especially higher Amp's).....The PCM is faulty or You have a bad ground.

These transmissions may be eating pumps for some reason.....Like engine/trans alignment issues, Are both dowels present & in good shape??
Flexplate runout?
Inspect the pump gears, pump bushing, & pump body for wear/damage.

Check the Boost Valve Sleeve for being loose in the bore, The will cause Torque Signal oil to leak & cause low line pressure when the unit is hot.
Same with a loose Pressure Regulator Valve.

4L80E Reverse Bands are not suitable for plowing duty, Use a TH400 "Grooved" Band.

Check the Forward Drum for damage where the Input Shaft & seals ride, VERY commonly over-looked & will cause repeat Forward Clutch failure.

Use Raybestos grooved HD frictions in commercial applications (Forward, Intermediate, Directs)

Do not use 4 frictions in the Intermediate Clutch, Use 3 TH400 frictions, Wave Plate, Steels & Backing Plate. The 4 friction set-up is great for holding power BUT no so much for a HD set-up.

Set your end-play correctly!!!!! TH400/4L80E will beat themselves to death with to much end-play, Very quickly in a plow truck that is shifted from forward to reverse a million more times than a regular truck.
http://www.sonnax.com/articles/408-p...-train-failure

[rickpilgrim]

Thanks for the tips- I really appreciate them! Have made a copy to pass on to my new Trans guy for my 2002 GMC k2500 trans this summer. We don't rebuild our own due to time, either buy reman or send out.
Wish you had a shop here!
Thanks Again!

[rickpilgrim]

Thanks for the tips- I really appreciate them! Have made a copy to pass on to my new Trans guy for my 2002 GMC k2500 trans this summer. We don't rebuild our own due to time, either buy reman or send out.
Wish you had a shop here!
Thanks Again!