1989 chevy silverado k1500 autotrans

[Ezrider_92356]

on my 1989 silverado k1500 350 automatic over drive transmission when on the interstate and in overdrive if i press the gas over like 1/4 throttle it slips it acts like it kicks down a gear but if i drop it out of overdrive the rpms come up a little bit more. would this be the torque converter unlocking for some reason or do i have bigger problems. i bought the truck with a blown head gasket and high millage but i had a rebuilt (well about 40,000 mile) 350 so i put that in there the trans had a sticker on it saying it was rebuilt and by what company and such on the bell housing and was pretty grease free unlike the old engine. i had never takin it on the interstate with the blown headgasket only around town enough to make sure that everything was functional on the truck. after the swap it took me a bit of messing around with the throttle valve cable to get it shifting like it used to. i mention that thinking maby my throttle valve cable still is not adjusted properly

 

[TilliamWe]

Re: 1989 chevy silverado k1500 autotrans

The small increase in rpms when you push down the throttle at highway speed sure sounds like the torque converter unlocking. That is how they are supposed to operate. Converter unlocks in 4th before a full downshift to 3rd happens. But you can't let it run in 4th with the converter unlocked, that'll cause excessive heat and burn up the trans.
Test it by running on the Interstate, and pressing the brake pedal down just enough to turn on the brake lights, but not actually slow the vehicle. The torque converter should unlock then too.
If the converter is locking and unlocking a lot, that's bad. It'll get the trans hot and ruin it. Most of the time the locking and unlocking is caused by the motor not being powerful enough.
Best of luck to you.

 

[Ezrider_92356]

Re: 1989 chevy silverado k1500 autotrans

well its a big increase in rpm's almost as much as a full down shift i have to let off the gas and re apply to get it to get it to stop slipping or however you want to discribe it. its not lack of power the motor has alot of pep has no trouble smokin 33's from a stop light and im talking about doing 75 up a slight grade pressing the throttle about 25% driving unloaded. normally i dont pull light loads with that truck for light loads i normaly use my 95 gmc siarria 1500. normally if im towing with that truck im towing 6-7000lbs running with in drive not over drive. with no problems the only time i have trouble is in overdrive

 

[dolluper]

Re: 1989 chevy silverado k1500 autotrans

Your TV cable may be set a little tight,lock up should come in about 51 MPH {82K}it will haunt around that speed {in and out}manifold pressure will affect the locking and unlocking also

 

[Ezrider_92356]

Re: 1989 chevy silverado k1500 autotrans

so i should try loosing the tv cable some and look for any vacuum leaks?

 

[dolluper]

Re: 1989 chevy silverado k1500 autotrans

First of all I would test drive it,by normal acceleration letting the trannie do it's work and see if it's locking at 82 km {51mph approx},you will feel it or the rpm's will drop.If it locks ahead of that speed loosen the tv cable or after that speed tighten it.The usually adjustment {static ,not running} is to hold the throttle wide open and just take the slack out of the cable or a little to the tight side, matter of pefference.Take it from there ,when the cable is right if it's not in proper operation then check for vac leaks

 

[Kenneth Brown]

Re: 1989 chevy silverado k1500 autotrans

Heinz- If dollupers methods don't fix it I highly urge you to get it to a tranny shop for correct adjustment. A misadjusted cable on a 700R4 or 4L60 (e) will ruin it extremely quick.

 

[dolluper]

Re: 1989 chevy silverado k1500 autotrans

89 with a 350 trannie {3 speed with locker} higher shift points than the 700's or their electric cousins

 

[Ezrider_92356]

Re: 1989 chevy silverado k1500 autotrans

the 350 is the engine size, it has an over drive 4 speed transmission i believe it to be a 700r4, it says hydromatic or something like that on the transmission bell housing on the gm rebuild sticker. when i adjusted the cable the last time i adjusted the way suggested but i found the shift points to be too soft. especially 2-3 so i tightened it a little more till it shifted firm but smooth. i assume im probably due for some new shift bands. or maby if theres a way to adjust them. probably tomorrow if i get a chance i will reset the tv cable to where its suppose to be and see if i still have the slipping problem in 5th. i was also thinking of trying to change the filter. when i did the engine swap i removed the transmission and engine as an unit separated them on the shop floor mated the new engine to the tranny and re installed as a unit i drained the transmission and torque converter in the process. but didn't change the filter, i wonder if a plugged filter could be causing the lack of pressure/too soft of shifts at proper tv cable settings. i also don't remember there being any vacume lines going between the motor and the transmission maby did i overlook one on the reinstall

 

[Ezrider_92356]

Re: 1989 chevy silverado k1500 autotrans

well i got back from my week long vacation i took. took some time to work on it today. i properly adjusted the tv cable tq locks at 50 mph but still the same thing at about 25 percent trottle at freeway speeds the tq converter unlocks so i moved the adjustment some more and now the torque converter locks at 45mph but the same thing at freeway speeds tq converter unlocks at 25% throttle. does the 700r4 have a vacume control on it it as well as the tv cable. i dont remember there being a vacume line when i installed the motor but there could be and i just dont remember. i should just go look but its cold outside. if there is i think im going to start by replacing the gasket between the tb and the intake manifold as i had the tb off but re used the old gasket. what are some of your thoughts i have some time to work on it tommorrow

 

[Kenneth Brown]

Re: 1989 chevy silverado k1500 autotrans

I fairly certain that theres no vaccum line to the tranny but do have advice. Replace that gasket! If you were in a real bad situation and had to reuse it it might be ok if coated with a thick grease but otherwise replace it. Google the name Burt Brown racing transmissions and shoot him an email. Burt knows everything thats ever been done to powerglides/350's/400's so I'm sure he's familiar with the 700 also. Let us know what he reccomends if it fixes it.

 

[Kenneth Brown]

Re: 1989 chevy silverado k1500 autotrans

By the way- There is no relationship at all between me and Burt till ya get back to Adam and Eve. Just the same name and a man I admire and have relied on to fix my circle track junk from time to time.

 

[Ezrider_92356]

Re: 1989 chevy silverado k1500 autotrans

i shot him an e-mail waiting for a response

 

[dolluper]

Re: 1989 chevy silverado k1500 autotrans

Me back to.The 700 is electrical and pressure ..no vac Locking in at 50 mph is the correct setting at 45 is not right, change her back.things that affect the torque solinoid switch{in trannie left side wires going to it}are your brake pedel adjustment , TPS {throttle postion sensor}settings, and ECM

 

[Ezrider_92356]

Re: 1989 chevy silverado k1500 autotrans

The early 700-R4 had issues, you need to install a shift improver corrections package by Superior or Transco / transgo there is a down shift valve and sleeve you can change also even Summit sells it. This is what I recommend. Burt

this is the reply i got from burt brown

dolluper the break pedal will lock and unlock the torque converter. if the tps was off that far seems like it would run like ****. but somthing to look into. would it be posible to wire a temperary switch to the solinoid to manualy lock it in to figure out if im dealing with an electrical or internal problem.

im remembering why i hate automatics im about tempted to do a 5 speed conversion. only thing iv ever had to do to manual transmisions is replace the cluch. i always seem to have some kind of issues with automatics

 

[dolluper]

Re: 1989 chevy silverado k1500 autotrans

Really it;s the different circuits that can have troubles,bad grounds or shorts or brake pedal adjusted improperly From what you say it almost sounds like the 4TH gear switch is acting up Check by doing and ohem check {with key on NOT running} then a voltage check with a high imped meter NOT A DIGITAL {won't work} jacked up in drive CHeck purple and dark green wires when in fourth,tap brakes also see readings on both tests

 

[Ezrider_92356]

Re: 1989 chevy silverado k1500 autotrans

will a regular anolong meater work, thats what i have. or do i have to get one that is spicifily an high imped meter?

 

[dolluper]

Re: 1989 chevy silverado k1500 autotrans

Give it a shot,it might but a digital won't work...or take it to a trannie shop and get them check the locker solinoid:{four gear switch}

 

[Windykid]

Re: 1989 chevy silverado k1500 autotrans

If I remember correctly the 700R4 does not have bands. It has clutch packs. Also I believe the owners manual will tell that in drive to accelerate pres half way down on the pedal. In overdrive you press 3/4 to full to accelerate. Definately change filters, as to maintain correct pressure.



Also since the original 700R4 came out, there have been over 20 modifications done.

 

[bruceb58]

Re: 1989 chevy silverado k1500 autotrans

will a regular anolong meater work, thats what i have. or do i have to get one that is spicifily an high imped meter?

A digital meter will work just fine. Pretty much any meter will work just fine for this application.