transmission and other stuff

[panchosteam]

Hi guys, i've been working on my 1986 k20 suburban on the past weeks: brakes, power steering pump,hoses new front shocks.... this week i had the transmission modulator replaced. It looks like who ever owned this truck never had replaced it. Before it used to feel like it was grabbing on to someting before take off and now it feels faster,the modulator i got is smaller and has a screw in the hole for the vacuum hose,you can adjust it depending on need of shift 1/4 turn to left to retard shift,1/4 turn to the rt and it is supposed to advance. The first day installed it felt very smooth, the only problem was that it shifted late, I called a transmission guy and he said to take the screw out and put it back and only turn it 3 times, this gave me a stiffer ride and better shift (feels on time)my problem now is that it leaks like crazy around the pan and the bolts that hold the pan are loose, it now rides a little hard but shifts ok. If i add fluid it feels better, but i don't know what to do. Does anybody know how many bottles of fluid this trans takes? i 'll have the gasket and fluid changed again then i'll go from there...i'm also looking for a place where to buy the sending unit, it has the big flat tank on the back,if any of you have replaced this and knows where to get it for good price please let me know. Thank you for your help

1986 k20 chevy suburban 6.2
1984 gmc sierra classic pick up 6.5 td

[john8662]

Transmission = TH400

I can't speak on the shifting quality on this transmission because I have never dealt with a 400, mainly 700's.

Anyways, a couple of things come to mind.

First off, get the fluid topped off before driving, the shifting abnormalities you're having could likely be because of a low fluid level.

The leak on the pan due to loose bolts should be fixed. You should be able to take a 13mm socket and snug them all. These bolts need no more than 15 ft. lbs of torque. It's possible that when the transmission was serviced that they didn't get all the bolts tight.

Leaks are no fun!

[dieselbegreat]

Yes, snug all those bolts up (just 15 ft-lbs) and if the leak keeps up, replace the gasket with a cork one and snug all the bolts up little by little all the way around. Tighten again in a few weeks. Replace the filter while you're at it. The fluid level should be checked with engine hot and idling in park/neutral. Add fluid to full mark but do not overfill.

My '88 has the same setup you have. Adjustable modulators are probably only good for a slight adjustment. The main adjustment for shifts (providing you vacuum pump is within spec!) is on the passenger side of the injection pump throttle shaft. The plastic unit has two 10mm bolts that loosen for adjustment fore and aft. Makes a BIG difference is driveability, but you seem to be happy with the way it is now.

[panchosteam]

Thank you guys, the transmission was serviced about 1 or 2 months ago,i even bought the deep stick because the one it had was welded at the end, i just wanted to have the right one so i wnt to the dealer and got it before it was serviced,i've checked the pan bolts every week and both times they were loose,the first time, i tight althe way around no torque meter, the second time last tuesday, loose again and looks like fluid was coming out from between the gasket and the housing(trans housing)i'll check tomorrow again, but for sure it will have a new gasket installed. I have to replace the spring leaf bushings too because oil leaks have destroyed them, does any one knows where to get the sending unit for this truck, and also the bushings?and yes it has the 400. I have replace the dampner pulley and the harmonic balancer and it still vibrates a little,next radiator flush.

1986 k20 chevy suburban 6.2
1984 2500 sierra classic pick up 6.5 td

[john8662]

Which sending unit are you talking about?

[panchosteam]

Hi John, i'm talking about the sending unit inside the diesel tank, so i know how much diesel i have,i don't like putting diesel every 3 or so days whit out knowing how much i have. Today i finally got the gasket and filter replaced (again) then i'll go from there.


1984 sierra classic pick up 6.5 td
1986 k20 suburban 6.2

[john8662]

The sender for how much fuel you have is in the tank, it's connected to a float. It's one of those drop the tank and remove the assembly. I don't know whether you can buy just the sender and float, but check with your local parts store will reveal whether you can or not.

Check all other electrical connections before you tackle that job.

Sometimes it's just the gauge in the cluster. A common problem with this vintage truck is the fuel gauge resister will burn out leading to the gauge still reading, but will only read to 1/4 tank. This leads to Empty still meaning empty but 1/4 meaning full and 1/8 meaning half a tank.

If you've got this symptom, there is a fix..

[panchosteam]

Hi guys, John that is what my gauge reads i've filled up althe way and it reads just a little more than 1/4 of tank, i tought about grounding the dash circuit board on the dash but i get home too late,and on the morning i don't have time,so i'll try to make some time and fix this,i disconnected the wire from under the suburban and turned the ignition on and the nidle went up altheway,that is way i concluded it must be the float or sending unit from the tank,i do mobile electronics installs so the ground problem if that's what it is will be easy, i will try to do this some time tomorrow, thank you for the help.

1984 sierra classic pick up 6.5 td
1986 k20 suburban 6.2

[john8662]

It isn't a ground problem if you've got the "1/4 tank" symptom.

It's an easy fix, done it myself on my '86.

I was lucky though, the parts were found locally at a local ma and pop kind of auto parts store. But anyways, there is a resistor on the back of the gauge, it looks like a flat piece of chalk (like welders chalk).

Anyways, it burns out and that's why the gauge only reads what it will read. You can replace the gauge, or just the resistor, which isn't available at the dealer. There is a kit called "fix-a-gauge" that includes a normal looking resister with leads to install in place of the oem one. They are availble online.

http://www.fix-a-gauge.com/

John

[panchosteam]

Thank you for the info,i have bad news from today,on the way to work i could feel the suburban a litle more heavy than usual and i tought i was related to the modulator on the side of the transmission,so i was driving from home to work and sudenly lose power and blue smoke, i noticed that it was also rathleing so i pulled over and pop the hood ,checked the fluids,every fluid was fine nothing rare on them,then i cracked the injector lines they all made a diference, what now?
i have no idea where to start checking, injectors maybe, fuel pump or rings?could some one help please?
1984 sierra classic pick up 6.5 td
1986 k20 chevy suburban 6.2 now with engine noise

[DmaxMaverick]

No good news from that. Sorry to hear it.

Replace the fuel filter, but don't be too optimistic.

Sounds like your IP let go. Yours is a textbook description of every DB-2 pump that left me. Just to be sure, though. Check the lift pump first. It can cause similar conditions if it's failed.