Need guidance on 700r4 swapped transmission issues

[71C10Guy]

I have a '71 C10 with a 350 and 700r4 swapped in. A few years ago I was pulling out of my driveway and suddenly lost drive and all other gears. I ended up letting it sit because I had just had the transmission rebuilt and I was pissed, then life got in the way and the whole ordeal was put on the back burner until recently.
Well I figured out the fluid pump isn't pumping by pulling the cooler line. So I'm wondering if anyone can give me advice on figuring out what in the pump went wrong and if I can fix the pump itself or if I need to just get a new one?

I don't know what the shop did when they replaced the transmission, it was a small shop in a small town but they claimed they had experience with 700s. I'm thinking there's no way they cracked the pump when installing the transmission as it lasted about a year and a half before it went out, and as far as I know it would have never worked if they did that. On the receipt it said they replaced the transmission with a reman instead of rebuilding my original one.

[Sheepdip]

Go to a local reputable transmission shop and let them sort it out, could be simple or not so simple. Just my .02 worth.

[71C10Guy]

Originally Posted by Sheepdip

Go to a local reputable transmission shop and let them sort it out, could be simple or not so simple. Just my .02 worth.

With all due respect and no offense intended, that really didn't help. It's a second vehicle so I'm not relying on getting the truck done asap. I also won't learn anything by taking into a shop and having them do it. Rebuilding a whole auto scares me, but I feel like (if it's possible or worth it) I could take a crack at rebuilding a pump. Worse case the truck sits for another couple weeks while I put a new pump in.
I work at a shop and have access to lifts and hydraulic transmission jacks on weekends. I have also already cleared time with my manager to do the job. This also isn't the first transmission I've dropped, replaced, or done fluid changes on. I'm just new to actually working on the internals so I was hoping someone could guide me in the right direction as to working on the pump and things to look out for, even if it's "you can't rebuild it or it's a waste of time".

Whether it's putting a new pump in or rebuilding the old one, I'd like to do the work myself so I can learn and gain more experience in my field. I do not want to pay for someone else to do a relatively simple job and learn nothing.

Regardless thank you for taking the time to reply and again, I mean no offense, I just wanted to clarify my position.

[nightmare]

First off, does it have enough fluid? Maybe try adding some and see if the truck begins to move. If it does, it may be sluggish at first, but that means you need more fluid. Low fluid will cause the problems you are having.

It's commendable that you are wanting to learn how to rebuild the 700R4s. They are very good transmissions, and if built right, can handle some serious power.

That said, I'd recommend getting a good book on GM Automatic Transmissions. I know with the internet it is feasible to "just google" what you are needing, but a good book helps tremendously too. I have the Haynes Techbook for GM Transmissions; it covers pretty much all transmissions prior to maybe 1988 or 1990. It does have a troubleshooting chapter, so that may be your first step. Anyhow, the ISBN is 1563924234.

[71C10Guy]

Originally Posted by nightmare

First off, does it have enough fluid? Maybe try adding some and see if the truck begins to move. If it does, it may be sluggish at first, but that means you need more fluid. Low fluid will cause the problems you are having.

I had drained the oil originally when the transmission went out. I was hoping to find loose linkage or something similar but didn't end up finding anything. When I got back to it recently the first thing I did was buy 12 quarts of fluid and put 8 in. I believe completely dry these transmissions take about 11? But seeing as I never pulled the torque converter I figured 8 would be plenty and it did show just over full hot while running in park and cold. I could be wrong but that should mean I've overfilled it, correct? I was trying to overfill it temporarily anyways just to rule out a mismatched dip stick or similar. Basically in my mind even if the levels on the dip stick were wrong, knowing I put 8 quarts in and should have overfilled it if I saw no fluid pumping I could be sure it was a bad pump and not just low oil.

Originally Posted by nightmare

It's commendable that you are wanting to learn how to rebuild the 700R4s. They are very good transmissions, and if built right, can handle some serious power.

That said, I'd recommend getting a good book on GM Automatic Transmissions. I know with the internet it is feasible to "just google" what you are needing, but a good book helps tremendously too. I have the Haynes Techbook for GM Transmissions; it covers pretty much all transmissions prior to maybe 1988 or 1990. It does have a troubleshooting chapter, so that may be your first step. Anyhow, the ISBN is 1563924234.

Thank you for the isbn. I'll start there and see what I can find!

[Richard]

700R4 uses a TV cable. Basically a throttle position sensor for the trans. If not adjusted properly it can lead to a short life. Good to learn new stuff, I have done trans rebuilds myself. TH350 and 4L60e. Everybody starts somewhere. Pump rebuild is pretty easy. Basically, the whole process is not bad. Just having/getting the knowledge and ability to know what needs to be replaced, what can be repaired and making sure everything goes where it should in the trans. In my honest opinion if you have the trans out and pump removed it would be a mistake to not go through the rest of it.

[71C10Guy]

Originally Posted by Richard

700R4 uses a TV cable. Basically a throttle position sensor for the trans. If not adjusted properly it can lead to a short life. Good to learn new stuff, I have done trans rebuilds myself. TH350 and 4L60e. Everybody starts somewhere. Pump rebuild is pretty easy. Basically, the whole process is not bad. Just having/getting the knowledge and ability to know what needs to be replaced, what can be repaired and making sure everything goes where it should in the trans. In my honest opinion if you have the trans out and pump removed it would be a mistake to not go through the rest of it.

Thank you for the advise! Considering it's supposedly a reman and at has at most 2 years / 15k on it is there anything I should specifically be looking for?
I do need to replace the TV cable. I noticed it getting frayed and the shop didn't replace it, and the last thing I need is to get this transmission done just for me to burn it by having the cable snap.

[MARKDTN]

Do you know what year it is? The pre-'87 700R4 are prone to issues and have a 27 spline input shaft. '87 and later have a 30 spline input. It is important that the TV cable be adjusted correctly when first installed. It controls pressure internally and can fail a transmission in a blink of an eye. If you have 8 qts of fluid in with an undrained converter and not getting fluid out of either line to the cooler, sounds like a pump issue. But that may only be the tip of the iceberg.

I am a pretty heavy mechanical guy. I have built many engines, not afraid to dig into lots of mechanical things-but automatic transmissions scare me. I would pull it and let a good transmission guy do the repairs-but that's me. A guy that knows his way around these may save you a lot of taking it out and putting it back in or even a failure because some tiny shim or clearance is critical.

Good luck with it.

[Rickysnickers]

Here's a thread that may interest you, https://67-72chevytrucks.com/vboard/...d.php?t=634121

[pjmoreland]

I rebuilt a 700R4 a couple of years ago. I purchased the instructional videos from Monster Transmission. They have the teardown video on YouTube.

https://youtu.be/NSS-gv1ekpM?feature=shared

[kwmech]

Originally Posted by nightmare

............... They are very good transmissions, and if built right, can handle some serious power.............. .

Not in my experience, a well built 'able to handle serious power' has a short life span.

Been through this several times personally. I wasted a lot of my money on these. They are not a truck transmission and should never have been used as such. Sorry for the put down

[57taskforce]

Originally Posted by kwmech

Not in my experience, a well built 'able to handle serious power' has a short life span.

Been through this several times personally. I wasted a lot of my money on these. They are not a truck transmission and should never have been used as such. Sorry for the put down

I couldn’t agree more. 700R’s are junk on a good day if you use your truck for anything truck related. I’ve been bitten by a few of them.

That said, compared to all the modern stuff they are pretty simple to rebuild. I’ve done 2 of them. Get a good rebuild guide for it and it’s not too bad.

[clay68c10]

The ATSG manuals are good. They have troubleshooting info as well as the step by step instructions for a full rebuild.

[R.O.B.]

If you lost both drive and reverse, it could be the torque converter. I had a 90 Mustang that that happened to. Just installed a new converter and all was back to normal. It actually broke the input spline shaft on the converter in half, so nothing was spinning on the transmission.

[lil hoodlum]

I would suspect your transmission fluid is not correctly filled.

I heard that the transmission fluid can drain out of a torque converter if it has been setting for a long time.


I would check the fluid level again and fill it to the proper amount. Maybe put the rear up on jackstands and put the transmission into gear for awhile and the recheck the fluid level after some time.

[425HP409]

If it quit forward and reverse all at once, you have a pump failure. I bought a new 76 Malibu and after 250 miles with no problems, the pump exploded. It had to have been cracked at the assembly line. A cracked pump can go for awhile before failing.

[leftybass209]

I had a 700r4 pump blow in my 69. It was nothing spectacular. I was already going maybe 30, went to accelerate and it felt like it was in neutral. I had no gears, but nothing happened; no jerking, no lunging or sluggishness. The shop said the pump looked original, but the trans had a few mods that suggested it'd been rebuilt before i got it. I didn't put more than 75-100 miles on the truck before the pump let go.

Any time I run across a 700r4 or 2004r I always assume at some point the TV cable wasn't adjusted correctly. Any time i see someone complain about 700s I think; they ran just fine off the lot when new, both 2 and 4wd. Even the best parts are junk if they aren't maintained.

I've used the TV made EZ cable stuff. The stuff makes the geometry full-proof and very easy to set and forget, or tear down and reassemble with no real worry of setting the cable correctly. It's not aesthetically pleasing though, and requires a separate baseplate under the carb.

[Accelo]

First, it did work. So the TV valve and cable is likely working. Even if it's not connnected the transmission will move both forward and reverse in a driveway.

First thing to check is to pull the bolts from the converter and see how far it will go rearward towards the transmission. You need to have less than 1/8" between the converter tabs and the flex plate. I suspect you may have lots more than this and the drive lugs have disengaged from the pump.
If you have more post how much and I can give you ideas where to go from there.

If you can not move the converter back you have serious issues. Let's not speculate just get the measurements.

[Dashman]

The actual distance between the torque converter and flex plate is not of concern because it should be shimmed. What is important is how much the torque converter comes out of the pump, and that should be about 1/8". In one of the linked videos the guy says 1/8 to 3/16", in the other video the guy says 1/16 to 1/8".

https://www.youtube.com/watch?v=afzBif5snOg

https://www.youtube.com/watch?v=efjVRicuFrA

As can be seen in this 2nd video, an incorrectly set torque converter can eat up a pump in a short amount of time.