Fastduramax

Ok 12 speed Guru's please help me out ! 88 RD688S 350 12spd pulled tranny out today and my replacement tranny is different in this way... It has a spring loaded plate against the housing that the input shaft passes through that the clutch brake presses against, the tranny I pulled out does not, the housing "snout" is actually longer making up for the space the spring loaded plate takes up on the rebuilt tranny so the clutch brake on my tranny presses against the housing instead of a spring loaded plate in other words.... Both TRTXL-1070B trannys, both have equal distance from either the spring loaded ring or housing snout on my tranny to the end of the input shaft... So million dollar question are they interchangeable with no other modifications? Thanks guys !!

Wow dragon 30psi SWEET ! What the hell is wrong with my turbo !!! And no i have NO boost leaks !

LMAO Ernie ! Yup Lucas has a liquid cure for everything WHAT A FREAKIN SHAM !!!

Kmon are you kidding me ! No one on here has ever tried a different turbo on their E6 350 !

I would also like to put out a public thank you to TREEMUNCHER who replied to my PM's with some very usefull info, great guy.... Oh and for not ripping on me for hijacking his thread LMAO !

By the way thank you fjh ! Great info as always ! I have not bumped my timing yet as my truck hauls ass right now with the fuel increase and other stuff I have done.... But you can prolly tell by my posts I can never stop tinkering so that will prolly be next on the "Mack do list" !

Well Bull Im still tinkering but here is an update.... The valve adjustment made no "seat of the pants" power increase but the motor sure is quieter.... Your "gov adj" did nothing for power either and EGT's did not move (5 turns out).... That said I think with moving my rack stop all the way forward and dropping my "ramp" all the way down I was already at full forward rack travel so the Gov screw had no effect ? Let me know what you think on that subject ! Warpman89, If I take my pump apart again I will take pics and post them for you, the directions Bullhusk and I gave are pretty good (I think lol) when you start taking stuff apart it becomes pretty self explanitory.... If you get into it and still have questions I will be more than happy to help best I can !

Ernie What are you seeing for no load full throttle RPM ? Im currently seeing 2200, a Mack mechanic told me years ago he likes to see 2300 ??

Makes total sense Ernie thank you.... Opened my pump back up and made the 2 1/2 turn adjustment, Ill report tomorrow night on any improvement I may see.... My ass is the only one in the seat of my truck ever and is fully equiped with autometer digital gauges so I dont mind playing around with power settings....

Any reason why 2 1/2 turns is the adjustment of choice ?

Counter clockwise ?

OK Dragon Im prolly gonna get torched for this post but here is what I did.... My 88 E6 350 RD tri-axle went fom being the best running but most under powered 350 Ive ever owned or drivin to running like a scalded dog and still have the EGT's in check.... Pull the return line off your Ambac and then the brass fitting off the pump, there will be a small spring that sits in a small cup, find 3 small washers that will fit in that cup drop the spring back in and slam it back together.... My pressure went from 17lbs at idle to 28lbs.... I popped the top cover off my Ambac and slid the rack stop all the way forward, loosened the 3/16 screw on the ramp slot and slid the ramp all the way down to now get FULL rack travel.... Also changed the air cleaner in the process.... I went from a max of 16lbs boost to 24lbs and that is with some damaged fins in the compressor side od the turbo ! Yesterday I also adjusted the valves which were WAY out of spec and pressurized the system for boost leak test, hoping I gain even more as I have not driven it yet since yesterdays work.... Holy shit this truck came to life way more than I expected freakin actually fun to drive again !!!

Same motor as my last 2 posts lol ! 88 E6 350 4 valve ATA Ambac injection system.... I was wondering if anyone has found a good turbo replacement part number to get a bit more boost and performance out of their 350 ? Current part number on my truck is 631GC5117.... I did slightly damage some fins on the front half of the turbo while changing the V clamp which Im hoping is to blame for my low boost situation seeing everything else has checked out normal ! Anyway if I am going to spend the money to have a turbo on hand I would like to go higher performance ! Thanks, Todd.

88 E6 350 4 valve ATA motor with Ambac pump, tag on motor and pump call for an initial timing setting of 18 degrees BTDC, I was wondering what you can safely bump the timing to for maximum performance ? Thank, Todd.

88 E6 350 4 valve ATA motor, I was wondering what the max sustained EGT is while pulling hills loaded and also what is a safe short "spike" in EGT.... As stated in a previous post I am reading EGT PRE TURBO NOT POST TURBO.... I know in my Duramax there is about a 300 degree difference between pre and post turbo readings, thus my confusion on my Mack motor, I dont know if this same number difference holds true on a Mack motor ? Thanks, Todd.

Thanks guys, here is the deal with mine.... There is only one anti tamper bolt in my pump and the rest are hex.... I tried the dremel trick before I posted, problem is the bolt is resessed into the cap so far that you have to use such a tiny cutting wheel you cant cut a bug enough slot into the bolt to get a screwdriver to bite ! Thats why I was wondering if someone knew where to get the special socket to remove the bolt....

Can anyone tell me where I can get the socket to remove the "anti tamper" bolt from the top cover of the pump ?

Hey guys checking back in as I finally rigged up a pressure gauge and here is the results.... 14lbs at idle 650rpm, 1700rpm produces the highest reading @ 27lbs, pressure gradually drops off to 23lbs @ 2100rpm.... Is this normal ??? Oh and one other thing for any trying this proceedure. use a liquid filled gauge ! A dry gauge will NOT work !!!

Kool I have some things to explore today ! Now, If my fuel pressure is low can it be adjusted or is it simply a sign the pump is getting weak ? Ambac pump by the way... Also the engine tag calls for 18 degrees BTDC of initial timing, was wondering how far you suggest to safely bump it up for maxximum HP gain ? This will of course be after any other issues are resolved....

Ok guys all good points... Rob, according to my restriction gauge, which does work, I have very little restriction under load at full throttle but Im sure it cant hurt to toss in a new filter... Rhasler, my truck is an 88 it is an air to air system... fjh, my truck will let a consistant belch of black smoke and clean right up as boost and rpm's rise just as any correctly running 350 I have ever driven, thats with the puffer turned on or off, seems to make NO difference... But I will try removing the puff limit bimbo if you think i need to try that, just not sure what a bimbo is unless you have recently spotted me dragging some local pig (bimbo) home from the bar.... I have no bluing anywhere and pyro never sees above 1150 BEFORE TURBO (I drilled and tapped manifold) which I know on my Duramax there is a 300 degree difference between before and after turbo readings... Think there is a lot of room to juice this thing up !!! And lastly fjh, where is the correct place and proceedure to measure pump pressure at ? Thanks again guys !

Thanks for the help guys.... Yup I am getting full throttle, like i said the truck has very low milage and last spring I went through all throttle linkage and shimmed any play I found with stainless washers and even replased the "gas pedal" lol.... Anyway even with the puffer issue resolved it should have no effect on my low boost issue.... Any other ideas ?

Thank you rhasler for the reply.... Yup I have taken the reversing relay all apart, thread taped and doped all fittings and put all back together.... wierd thing I found is there seems to be no boost leaks when checking with gas leak solution (thick blue soapy water) but when I shut the truck off the rear half of the reversing relay is sometimes leaking by but I believe that back half is pressurized by air pressure and not boost ? Looks rebuildable as the back half is threaded on and a relay I have kicking around in a parts pile is all one unit and cannot be taken apart....Another note, I have a gas cock plumbed between the reversing relay and pump so I can turn the puffer on and off with the twist of a knob, truck will belch the exact same amount of black smoke leaving a stop light weather the puff limiter is on or off !!!???

I have an 88 E6 350 4 valve in my RD688S and 17 lbs of boost seems very low to me ! Truck has very low milage and has NOT been turned up and timing is spec.... Anyway I was wondering if a max of 17lbs was normal for a stock 350, I have checked all the obvious stuff, fittings, hoses, clamps, pretty sure the intercooler isnt leaking, I am getting full throttle etc ! HELP ! Thanks, Todd.