servo and accumulator theory of operation - Competition Diesel.Com

mike_belben · 07-16-2014, 05:57 PM

i had a previous thread about this tranny but its been closed for some reason.

280hp work truck with 47re and stock converter/input shaft. im just about the reinstall the VB, did a transgo TFOD-HD2 with the command control governor mods.

i also did the 2nd gear lockup epoxy, SS boost valve coverplate with .082 hole for now. installed the sonnax lube valve and pressure plug. this VB already had a sonnax oversized 4 land switch valve when jasper reman'd it, and it also had the TCC vent hole (that transgo suggests drilling) epoxied back to stock so i chose to widen the separator plate vent slot ala sonnax rather than make a further mess of the VB passage by drilling. brian at sonnax said the transgo was fine with their parts, except not to do a super servo, its too harsh with the transgo. the guy at transgo always seems pretty gruff and doesnt want to talk. his answer was that nothing can be mix and matched and he didnt want to explain what anything i was modding was gonna do to shift quality. aka, leave me alone. i went middle of the road with all the hole sizes transgo spec'd, didnt do the reverse hole enlarging, and i did use their springs for everything except TV.

in the trans housing itself, transgo wants you to pound a restrictor orifice into the accumulator vent to sump. and also change springs. my accumulator only had the one larger spring, not the skinny inner. im installing a billet sonnax accumulator and front servo cover. question im having now, is which servo and accumulator springs to use. keep them stock or install the transgo's?

i realize that accumulator softens a shift, im just not certain whether a thicker spring will make a shift harder or softer.

anyone care to share their trial and error experience?

Kryp2nitE · 07-17-2014, 02:55 PM

Is this what you used?

SS boost valve coverplate:

If so you can not use a rigid band later on, it will not clear the plate. You will have to use a flex band (which a lot of people prefer anyway) I went with a rigid band from recommendation from a local builder.

I was told use the transgo triple red spring for Accumulator over this one that I had also ordered from PATC:

Not saying you have to do any of this, just adding what I found when I did my trans

mike_belben · 07-17-2014, 08:52 PM

well, i got it back together and drove it. i dare say it was better before.

backstory: reason i tore it down was no TCC lockup. i proved out the ecu, solenoid, wiring etc as good, so the next step was to see that nothing was broken, hung or tore up in the VB, which it wasnt. i replaced the OD/tcc solenoid bank and harness anyway, meter and test light verified them again, and did the shift kit all in one. i also spent a ton of time deburring and stoning all of the milled flats and cover plates.. they were horrible in terms of heavy cutter marks, burrs and dings etc. i spent 2 days looking up and going over EVERYTHING on this vb. all the bores and lands, etc. 100% disassemble/clean/reassemble. the worst wear was on the the pressure regulator valve which i replaced with the sonnax convertor charging unit, and also the stem of the 2nd gear servo where it plunges in and out of the servo cover, the steel had scores. i buffed that all back to smooth with 400grit and installed the sonnax billet cover with O ring. i used the transgo springs everywhere called for except the rear servo because i couldnt pull the lever without removing OD housing (still in truck.)

i set the line pressure seat at about .300" from flush using the transgo dual springs, shim and notched washer. i stopped there because the spring seat was hitting the rooster comb boss. well, it idled around 85-90psi (accumulator) and maxed around 130. leakage at the front servo is no more than 10psi from line pressure.. probably closer to 7psi avg. ive always felt my governor pressure was high, it comes down to zero as it should, but at road speed its almost always 2psi per mile per hour. i see 80 or more in the governor nearly all the time just cruising 40mph. unfortunately my torque convertor still isnt locking up. im ready to believe its smoked. i just drained the fluid and blew out the convertor and cooler passages again and have lots of aluminum and a bit of black clutch material i assume.. looks like pepper. i drove it about 7 miles on new dex/UTF @20/80

first gripe, the shifts are very soft. dont think theyre slipping but theyre like stock. it was firmer before with a little less line pressure and no shift kit. the line pressure is much more erratic now too.. it jiggles all over the place. i drove it 1000miles back home from the trip that the lockup failed on, and its always been more stable than it is now. i tried a few settings on the TV cable and it responded normally but still erratic line psi.

2nd gripe. it wont backshift to second, atleast not when i want it too.. still seems to be auto shifting based on governor pressure. it will however, drop down to manual first at any speed and lock up the assend with a fury. i wanted this option in the event of blown brake hose.. had a real close call with no brakes once and trans wouldnt drop to low.

anyway. i ground the pressure regulator spring seat to clear the rooster comb boss and will crank up the line pressure. the new fluid is filtering through a sweat shirt right now to get the trash out and im contemplating going back to the OEM 1-2 and 3-4 accumulator springs to see if can get it to shift with some authority. im under the impression the huge stiff springs from transgo are softening the shift by counteracting the fluid pressure. gonna tighten up the bands a bit also, the transgo spec seems too loose to me.

i have to save for a convertor and overhaul parts as i just cant swing it right now, kids to feed. need to drive the truck whether i like it or not.

07-16-2014, 05:57 PM	#1
mike_belben Name: mike_belben Title: Green Behind the Ears Status: Not Here Join Date: Aug 2011 Member`s Gallery Posts: 96	servo and accumulator theory of operation i had a previous thread about this tranny but its been closed for some reason. 280hp work truck with 47re and stock converter/input shaft. im just about the reinstall the VB, did a transgo TFOD-HD2 with the command control governor mods. i also did the 2nd gear lockup epoxy, SS boost valve coverplate with .082 hole for now. installed the sonnax lube valve and pressure plug. this VB already had a sonnax oversized 4 land switch valve when jasper reman'd it, and it also had the TCC vent hole (that transgo suggests drilling) epoxied back to stock so i chose to widen the separator plate vent slot ala sonnax rather than make a further mess of the VB passage by drilling. brian at sonnax said the transgo was fine with their parts, except not to do a super servo, its too harsh with the transgo. the guy at transgo always seems pretty gruff and doesnt want to talk. his answer was that nothing can be mix and matched and he didnt want to explain what anything i was modding was gonna do to shift quality. aka, leave me alone. i went middle of the road with all the hole sizes transgo spec'd, didnt do the reverse hole enlarging, and i did use their springs for everything except TV. in the trans housing itself, transgo wants you to pound a restrictor orifice into the accumulator vent to sump. and also change springs. my accumulator only had the one larger spring, not the skinny inner. im installing a billet sonnax accumulator and front servo cover. question im having now, is which servo and accumulator springs to use. keep them stock or install the transgo's? i realize that accumulator softens a shift, im just not certain whether a thicker spring will make a shift harder or softer. anyone care to share their trial and error experience?

07-17-2014, 02:55 PM	#2
Kryp2nitE Name: Kryp2nitE Title: Green Behind the Ears Status: Here Join Date: Oct 2012 Location: San Diego, CA Member`s Gallery Posts: 64	Is this what you used? SS boost valve coverplate: If so you can not use a rigid band later on, it will not clear the plate. You will have to use a flex band (which a lot of people prefer anyway) I went with a rigid band from recommendation from a local builder. I was told use the transgo triple red spring for Accumulator over this one that I had also ordered from PATC: Not saying you have to do any of this, just adding what I found when I did my trans __________________ 95 2WD HE351/BHT3B twins, OFV060HP, Built 47RH, Airdog 150, 18* Timing, AFC Live Stage 2 Last edited by Kryp2nitE; 07-17-2014 at 02:56 PM.

07-17-2014, 08:52 PM	#3
mike_belben Name: mike_belben Title: Green Behind the Ears Status: Not Here Join Date: Aug 2011 Member`s Gallery Posts: 96	well, i got it back together and drove it. i dare say it was better before. backstory: reason i tore it down was no TCC lockup. i proved out the ecu, solenoid, wiring etc as good, so the next step was to see that nothing was broken, hung or tore up in the VB, which it wasnt. i replaced the OD/tcc solenoid bank and harness anyway, meter and test light verified them again, and did the shift kit all in one. i also spent a ton of time deburring and stoning all of the milled flats and cover plates.. they were horrible in terms of heavy cutter marks, burrs and dings etc. i spent 2 days looking up and going over EVERYTHING on this vb. all the bores and lands, etc. 100% disassemble/clean/reassemble. the worst wear was on the the pressure regulator valve which i replaced with the sonnax convertor charging unit, and also the stem of the 2nd gear servo where it plunges in and out of the servo cover, the steel had scores. i buffed that all back to smooth with 400grit and installed the sonnax billet cover with O ring. i used the transgo springs everywhere called for except the rear servo because i couldnt pull the lever without removing OD housing (still in truck.) i set the line pressure seat at about .300" from flush using the transgo dual springs, shim and notched washer. i stopped there because the spring seat was hitting the rooster comb boss. well, it idled around 85-90psi (accumulator) and maxed around 130. leakage at the front servo is no more than 10psi from line pressure.. probably closer to 7psi avg. ive always felt my governor pressure was high, it comes down to zero as it should, but at road speed its almost always 2psi per mile per hour. i see 80 or more in the governor nearly all the time just cruising 40mph. unfortunately my torque convertor still isnt locking up. im ready to believe its smoked. i just drained the fluid and blew out the convertor and cooler passages again and have lots of aluminum and a bit of black clutch material i assume.. looks like pepper. i drove it about 7 miles on new dex/UTF @20/80 first gripe, the shifts are very soft. dont think theyre slipping but theyre like stock. it was firmer before with a little less line pressure and no shift kit. the line pressure is much more erratic now too.. it jiggles all over the place. i drove it 1000miles back home from the trip that the lockup failed on, and its always been more stable than it is now. i tried a few settings on the TV cable and it responded normally but still erratic line psi. 2nd gripe. it wont backshift to second, atleast not when i want it too.. still seems to be auto shifting based on governor pressure. it will however, drop down to manual first at any speed and lock up the assend with a fury. i wanted this option in the event of blown brake hose.. had a real close call with no brakes once and trans wouldnt drop to low. anyway. i ground the pressure regulator spring seat to clear the rooster comb boss and will crank up the line pressure. the new fluid is filtering through a sweat shirt right now to get the trash out and im contemplating going back to the OEM 1-2 and 3-4 accumulator springs to see if can get it to shift with some authority. im under the impression the huge stiff springs from transgo are softening the shift by counteracting the fluid pressure. gonna tighten up the bands a bit also, the transgo spec seems too loose to me. i have to save for a convertor and overhaul parts as i just cant swing it right now, kids to feed. need to drive the truck whether i like it or not. Last edited by mike_belben; 07-17-2014 at 08:55 PM.