Downshifting 4l80.
07-07-2011, 08:04 PM
#12
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I've never seen the sprag issue, but I never really dropped a 4L80E to second on a regular basis. 3rd for grade and 1st in sand. I wasn't arguing with you, I couldn't see your posts yet and didn't even know somebody else was contributing at all.
07-07-2011, 08:31 PM
#14
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i did it to mine all the time... i didnt do it where the rpms would go to reline though.. i would do it with in reason.. and shes still running strong today!
07-07-2011, 09:31 PM
#16
Theres no way it can be harder on a trans to down shift then if you punch it and it shifts into second under wot power. like said above if you do it within reason it wont hurt it. The new trucks even do it by them selfs with tow/haul on, same basic trans.
07-08-2011, 01:59 AM
#18
Guys.....downshifting 4L80Es for Newbs:
Assuming you are cruising along in 4th gear:
Downshift to 3rd: Releases the 4th gear clutches, brings on the Over-run clutches - no danger unless the Overruns come on faster than 4ths release (stock feed/release holes it should be fine) at most speeds.
Downshift form 3rd to 2nd: Releases 3rd clutches, brings on 2nd band. Direct drum goes from input shaft RPM to dead still. The higher the RPMS, the more the load. 2nd Gear also uses an intermiate sprag, so that the 2nd clutches don't have to come off for 3rd gear (and above). Sprags hate 3 things: rapid unloading/loading (like spinning tires), high line pressure (brings on 2nd gear clutches faster), and 3, high RPMs. A constant speed downshift (not accelerating or decelerating) is the easist on the sprag at speed.
Downshift from 2nd to 1st: Releases the intermediate clutches, and intermediate band. Brings on Low band. Direct Drum goes to 85% opposite of engine RPM. I only recommend going to manual first from a dead stop or a very slow roll (sometimes the low band comes on faster than the 2nd clutches release, locking up the trans, burning up the low band).
Assuming you are cruising along in 4th gear:
Downshift to 3rd: Releases the 4th gear clutches, brings on the Over-run clutches - no danger unless the Overruns come on faster than 4ths release (stock feed/release holes it should be fine) at most speeds.
Downshift form 3rd to 2nd: Releases 3rd clutches, brings on 2nd band. Direct drum goes from input shaft RPM to dead still. The higher the RPMS, the more the load. 2nd Gear also uses an intermiate sprag, so that the 2nd clutches don't have to come off for 3rd gear (and above). Sprags hate 3 things: rapid unloading/loading (like spinning tires), high line pressure (brings on 2nd gear clutches faster), and 3, high RPMs. A constant speed downshift (not accelerating or decelerating) is the easist on the sprag at speed.
Downshift from 2nd to 1st: Releases the intermediate clutches, and intermediate band. Brings on Low band. Direct Drum goes to 85% opposite of engine RPM. I only recommend going to manual first from a dead stop or a very slow roll (sometimes the low band comes on faster than the 2nd clutches release, locking up the trans, burning up the low band).
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