700r4 issues

[firebird]

Got a 700r4 with a lock up switch on the dash in my 87 (3/4 ton, 350sbc). It was missing second gear. Bought a supposedly rebuilt 700 (seals, gaskets looked fresh. TV cable moved etc) from i hope a reputable guy. Its supposed to have new clutches, bands, a shift kit, and corvette servo. Its a 1990 K case original 4x4 tranny. The guy new what i had for a truck, he worked for a local dealer and was their tranny guy ands now retired.

Removed old tranny and put rebuilt in. Took it around the block and it shifted 1 2 3 but couldn't get going fast enough for 4th until i got out onto the main road. It would not shift into 4th, you could go WOT and the truck pretty well held its speed. Like i had the brakes on. I tried the lock up switch and nothing either.

I turned around and had only 1st gear. Got out and could have fried an egg on the tranny pan and limped back to the shop. Thought we got the tv cable set right. Hope i didn't cook the new tranny it only run 10 minutes.

Checked tranny oil and it was over full. Initially when filling we stopped at full mark which was 9 litres with engine idling.

Transmission is overheating and quit shifting. Tomorrow morning when its cooled i will see if it shifts 1 2 3 again. But why don't i have 4th, lock up switch not working and tranny overheating.

Had my father in law and my wife uncles with me. 2 are mechanics and the other an electrical engineer with 105 years combined wrenching on and racing cars. None of us are transmission guys. I will be calling the fellow i bought the tranny from tomorrow and not sleeping tonight.

Old tranny never did any of this. Just missed second gear. Would run down the highway doing 70-80 mph just fine.

 

[yevgenievich]

If tv cable was not set correctly then 10min. Could have cooked it. But sounds something else might be at play. For filling it, there is a full line for hot and one for cold. If the stick only has a line for hot, make sure vehicle is up to full operating temp when checking the level. The transmission might be wired for lockup to work only in 4th gear, so without 4th engaged lockuo switch on the dash would not do anything. Start testing fresh next day making sure tv is set correctly and try to get up to 4th gear. Might need different weigjts on the governer if it is trying to shift too high.

 

[firebird]

Going to head out in 10 min.

Put 5 litre in before starting, had a half litre in the torque converter to start. Then slowly added with it running probably wasn't up to road temp.

First thing I'm going to check is TV cable again and oil level.

3rd just felt like you had the brakes on.

I seen someone on here was driving around without the TV hooked up and another one with a broken connector on the throttle. How'd those guys make it and mine overheated in 10 min? If mines not set right? And if the governors set wrong?

It was perfectly fine reverse, 1 2 3 all shifted smooth and downshifted around the neighbourhood. Then no 4th on the main road. Then quit shifting and got damn hot.

 

[firebird]

Update- reconsidered last night and figured we didn't over temp the tranny it was just hot to touch pan. Did not burn the oil.

Saturdays trial and error:

Checked oil level- over full cold- drained 1L- started truck and warmed up- re added 1 L and dipstick red fine in "HOT"- level stayed the same throughout testing. Cant figure out why it read overfull then with the oil removed and the exact same re added it read full. Repeatedly checked trans temp with laser heat gun and it stayed steady around 100 F.

Re set Tv cable- plastic adjustment was pretty well all the way inside the body- Tranns would not shift into 2nd unless I let off the throttle around 40 KM/H- would not up shift out of 2nd.

TV cable set around 1/4" to 3/8" of plastic out of body- trans shifts from 1st to 4th around 25-30km/h (feels about right speed but wtf happened to 2nd and 3rd)- motor lugs until up to speed and rolls right along 120 km/h- only downshifts into 1st when slowed back down.

Tv cable set with plastic 1/2" + plastic out of the body- trans shift 1-2 with foot steady on throttle around 40 km/h (way to high speed and RPM as far as I'm concerned) and will not upshift out of 2nd.

Transmission rebuilder that i bought it from is going to come out Monday and wants to look at the throttle valve in the tranny.

I seem to have no 3rd gear.

 

[chengny]

In the original post you say:

Removed old tranny and put rebuilt in.

But, you didn't mention the reason why the "old tranny" was changed out. I'm sure you didn't change transmissions because it's a fun job and you like to spend money. So would it be safe to assume that the previously installed transmission suffered a catastrophic failure - or was at least damaged badly enough that it wasn't worth rebuilding?

If that is the case, the next question is - did you do a thorough flush of the transmission cooler and connecting tubing? If not, you need to do that now.


While the performance of the engine coolant section of the radiator is easily observed, the condition of the transmission cooler section is not so apparent. Proper operation (and normal life expectancy) of the transmission depends on the cooler allowing for the full designed flow rate through the tubes.

If a vehicle suffers a catastrophic failure of the transmission, it is imperative that the ATF coolant section of the radiator be thoroughly flushed as part of the transmission replacement procedure. The tubes that are used in the ATF cooler are tiny. Any debris that results from a serious transmission breakdown will quickly migrate to - and plug up - the cooler tubes. The result is that the new transmission will fail soon after being replaced.


Before operating the truck again, take the time to do the flush.

You should disconnect the coolant lines - at the transmission end - and flush through them and the cooler. Use a small pump, a reservoir and a strong solvent (acetone, MEK, etc). Before you begin, blow them out with compressed air and note whether any debris comes flying out.

IMPORTANT: Whenever flushing/ blowing out any tube type heat exchanger, the flow of flushing media must be counter to the normal fluid flow.


The bottom port/line on any transmission is pressure feed out - and it goes to the bottom of the cooler. The top port/line is the return feed from the cooler. This design continuously eliminates any entrained air from the cooler which ensures maximum efficiency of the heat exchanger.

So the flow of the flushing agent should be: in at the top of the cooler and out from the bottom.

 

[yevgenievich]

Also, here is a good article on tv adjustment
http://www.tvmadeez.com/article/

 

[firebird]

TVs been all the way in and out one click at a time and disconnected. The cooler lines were disconnected and drained when old trans come out. Oil looked clean so never bothered to flush. I don't think it ever did overheat I know initially I said i thought it did. As for debris, im guessing your saying something could be plugged in the tranny?
Old trans was missing second for a long time and going to cost me as much to rebuild it as a different rebuilt one ready to go in. I was hoping it was going to be a simple swap. The seller is coming out Monday he seems to think its the throttle valve in the trans, he was a mechanic for a chev dealer when these trucks were in their prime. Hope it's something stupid and easy.
From what I understand there's no band on 3rd and its not a clutch pack cause I have 4th gear. The TV cables doing funky things but at no point is the trans shifting correctly, and with it disconnected its not much different. So I'm thinking I can rule that out.

 

[yevgenievich]

Driving with cable disconnected or adjusted for too low of pressure will damage the transmission unless driven at almost idle. First time out you had all, but 4th, but now some missing in between. From begining it is also possible that there is a crossleak inside.
I generally set tv by feel, and makibg sure full pressure at full throttle. Article explaines its operation in detail.
Let us know what the builder finds.

 

[firebird]

Was away on holidays but got back to the truck today. Pulled the tranny at the transmission builders shop. Band was toast. He's going to troubleshoot why it burned up in 10 min.

 

[firebird]

Okay update.
Trans builder had check ball in wrong spot. I guess that's why it wore the band out. And we are back to the initial issue of no 4th gear.

Shifts 1-2-3 and then no proper 4th. It holds you back like I initially said, like the brakes are on. Then downshifts fine when you let off.

I'm not working on this trans anymore just repeating what the builders telling me.

 

[Jrgunn5150]

Okay update.
Trans builder had check ball in wrong spot. I guess that's why it wore the band out. And we are back to the initial issue of no 4th gear.

Shifts 1-2-3 and then no proper 4th. It holds you back like I initially said, like the brakes are on. Then downshifts fine when you let off.

I'm not working on this trans anymore just repeating what the builders telling me.

This is almost certainly a valvebody issue.

 

[firebird]

3/4 clutch pack clearances were way to tight. I guess not allowing the spray to freewheel in 4th. The builder bought the clutches and kit and dropped it in, didn't think about it. Removed a plate replaced with thinner one and clearances checked and trans is in the truck and working. What a f---ing ordeal.