Diesel rattle and transmission detent??

[Subzilla]

Finally test drove the Sub with the fresh head gaskets, rebuilt 6.5 heads and ATS turbo installation. I have 2 concerns.

First, she purrs like a kitten at idle. At half/full throttle, she rattles considerably more than it use to. I’m wondering if the fresh 6.5 heads have anything to do with this?? I didn’t touch the IP adjustment during the project. Just tried to retard the IP timing a line’s width and it didn’t seem to help. Should I keep retarding it until it quiets down? The engine has 305k miles on it and old heads were factory original and untouched.

Second, the transmission (700r4) is sliding from 1st to 2nd and then to 3rd AND it won’t downshift from 3rd to 2nd or 2nd to 1st at full throttle depression. The detent cable bracket was removed during the project as it is sits with the GP controller (’83 version) on top of the head. It was moved quite a bit during the reinstallation. I tried to adjust it – push the button, pull the cable sleeve toward the firewall, then depress the pedal to the floor. The sleeve didn’t appear to move in the bracket at all. Further inspection shows quite a bit of play in the actual steel cable from the bracket to the IP. Should there be any play or should the steel cable be tight? What can I do to fix this? It was working fine before the project so I’m not sure if I loosened something up as I was moving it out of the way or pulling on it.

[argo]

The steel cable you are referring to is a linkage. It should move forward when the throttle is applied, but it can also move forward on its own (it is slotted). This is a bit difficult to explain. Basically the linkage works like the linkage for a vacuum break on a carburetor choke. To check it to see if it's installed correctly (or didn't get knocked off) get an assistant to work the throttle for you. manually pull back on the linkage, and try to hold it. Have your assistant floor the throttle. If the linkage pulls forward when the throttle is applied, then it is functioning properly. If it doesn't, it may have been dislodged during your head job.

As for the rattle: Did you re-use the pre-combustion chambers from your old heads, or did the new heads come with chambers? If the new heads came with chambers, and they are of the later design with a larger throat area, perhaps it makes the combustion more audible? You might need someone else's input on this.

[Subzilla]

The cable is connected and moving with the throttle. I tried to adjust it several times yesterday with no success. It's almost as if the steel cable is too long or the plastic connector has been damaged and allowed the cable to shift backwards.

These were professionally rebuilt heads with the 6.5 pre-cups. They do have the larger opening compared to the 6.2 - I think they had the T on them.

[argo]

The cable is connected and moving with the throttle. I tried to adjust it several times yesterday with no success. It's almost as if the steel cable is too long or the plastic connector has been damaged and allowed the cable to shift backwards.

The cable housing might be damaged then. The lucky thing is that these T.V. cables are not diesel specific items like they were on the Oldsmobile diesels, so getting a new one won't be too difficult. As a temporary fix, you can wrap a hose clamp around the back side of the T.V. cable housing and get an assistant to floor the throttle, while you pull the casing back until it's tight and tighten the hose clamp (I have done this before, and it will work, but it's difficult if you don't have three hands). The problem is that it will slip with time and vibration, so it is a temporary fix only! Good for about 1-2 weeks while you get a new cable. Installing the new cable is a snap. They are really easy.

As for the noise: Did you by chance change ther timing chain? If so, perhaps the timing had been advanced in the past due to slack, and is now too far forward with a fresh chain. It also could be that the lack of induction noise with the turbo setup is allowing you to notice other noises that you previously couldn't hear.

[john8662]

6.2's and 6.5's sound different, and the main reason is that the cylinder heads are different.

The 6.5 heads have a different precup and different injector angle into the heads. This new angle, coupled with a redesigned precup leads to a few desireable things. The engine is actually more efficient, and starts better. Some are more rattly than others though, I think you're probably fine though, it's just going to sound different now.

Transmission...

I'm living this misfortune myself. A high mileage TH700 that was working ok until I had to freshen up the injection pump and injectors on a 1991 6.2 n/a. Now the TV won't adjust (gets like maybe one click). Brand new GM OEM TV cable, dropped the valve body and installed the Transgo Shift Kit JR, didn't help one bit in that department. Shifts badly and won't do proper downshifts as you're describing. I parked it while I figure it out or buy a new transmission.

If it wasn't for the TV cable the TH700 would be a good box, the 4L60e was a marvel in this regard.

If you figure something out before me, lemme know.

J

[Subzilla]

Put on timing gears some 10 years ago or so. No new chain. Guess I'll get use to the noise.....and the power:D My Blazer is so quiet compared to the Sub....

Argo, what are you referring to when you say the TV cable housing? Are you talking about the plastic retainer that "ball snaps" onto the throttle linkage or the adjuster mechanism? I'm trying to understand exactly your procedure.

It appears the plastic retainer has some age on it as it is cracked so I'm wondering if the retaining crimp on the end of the cable has shifted causing the steel cable to "reel out" (more steel cable available). And therefore at WOT, the TV is not maxing out as the cable is longer???

I'm gonna do more underhood studying tonight.

Thanks!

[Subzilla]

Fixed it! It was what I suspected - the cable retainer as it connects to the throttle linkage. The cable has a crimped stopper on the end and had been moved closer to the opposite end of where it should be. This essentially lengthen the cable. It should have been at the larger end of the retainer closer to the IP. Guess a picture would better explain it. Anyway, I moved it, tried to let self-adjust (next paragraph), drove it and now have normal shifting with 2-1 & 3-2 downshifts.

The thing that concerns me is that I still got no clicks when I WOT'ed the lever. I guess the WOT must have the TV fully out at that very position - just a coincedence, I guess. It's been running like this for a good 100k miles but I am getting the required downshifts. I'm thinking I should still put out $35 for a new cable to get a better margin of safety.

John, I don't know if any of this helps you or not!!

[DmaxMaverick]

There shouldn't be any "clicks". The TV (throttle valve) should be smooth between the extreme throws. The only "detent" is the range shift input (gear selector). If your TV clicks, it's broken.

The TV is not a "kick down" or "passing gear" switch. It is a variable pressure valve that operates throughout the throttle position range. Although, WOT should cause a downshift to the lowest gear available for a given speed, if correctly adjusted.

[Subzilla]

Guess I didn't word that correctly. The clicks I'm referring to are for the adjusting procedure. I pushed the adjuster button and pulled the cable sheath toward the transmission, then WOT the lever to properly adjust the cable listening for the clicks as it the sheath is being pulled out.

No, my cable is not broken. I understand it is critical to get it at the correct setting to signal the TV to apply pressure to the clutch bands at the proper rate relative to the throttle. I was just using the "downshifting" reference to confirm that it was operating correctly. The true way would be to put on a pressure gauge and check the various pressures. I'm not the expert here but I've been reading like crazy trying to diagnose my problem. This website has a great explanation of how the TV system works:
http://www.bowtieoverdrives.com/index.shtml

Thanks for the help!!

[6.5TDTahoe]

The Throttle Pressure is supposed to be set with a gauge.Specs in GM manuals. I would suspect the 700 may have incorrect co mingled parts in the throttle valve& governor system. Many opportunities since 1982 to be damaged or just incorrect parts installed. They don't need Shift kits if all parts are correct for application. The most fuel effecient 700r's were the ones with second gear lock up @ 15mph. Lock up speed/malfunctions can cost 3 to 5 mpg in town or urban operating conditionsI owned several new & used early 6.2 trucks. Also owned & operated an automatic trans shop starting in 1976 to 2000. Installed ATS turbo systems. towed around @ 80 MPH , 3400LB. drag car on open trailer@ 18MPG!!!! Truck ,car, trailer weighed around 12000 lb.Had a 2.73 rear axle ratio & would pull the California"Grape Vine south bound around 70MPH in Direct(3rd) gear,CONVERTER UN LOCKED.( 1to 1) hARDLY ANY PLACE place to drivel @ THAT SPEED lol. nO TRANSMISSION FAILURES IN THOSE YEARS!!!