700R4 Information Thread

[Broken85]

Nick,
I recently got the 700R4 from my 85 K10 rebuilt. Transmission is installed and before I moved it, I pressure tested the trans per your guide and dialed in the TV cable. Here are the results;

1. Park/Neutral/Drive/3rd - 85lbs @ 1,000 RPMs
2. Reverse- 140lbs @ 1,000 RPMS
3. 2nd and 1st gear low - 110 @ 1,000 RPMs and at full TV extension

#1 and #2 above are near perfect according to your guide. #3 should be between 160-295 lbs, but I don't think I am going to get there.

I decided to take it for a drive, and it is running perfect from what I can tell. I can barely tell when it shifts it is so smooth, no slipping at all. Is 110 a deal breaker? Is it only a matter of time before it burns up? What would early symptoms look like? I took it back to the guy who rebuilt it (who will not remove or reinstall it that **** job is on me so trying to avoid it) he is going to put it on a lift next week and pressure test it himself, but if #1 and #2 are in spec, and I don't think there is anything else I can do to improve the 2nd and 1st gear pressures with just TV adjustments.

 

[NickTransmissions]

Nick,
I recently got the 700R4 from my 85 K10 rebuilt. Transmission is installed and before I moved it, I pressure tested the trans per your guide and dialed in the TV cable. Here are the results;

1. Park/Neutral/Drive/3rd - 85lbs @ 1,000 RPMs
2. Reverse- 140lbs @ 1,000 RPMS
3. 2nd and 1st gear low - 110 @ 1,000 RPMs and at full TV extension

#1 and #2 above are near perfect according to your guide. #3 should be between 160-295 lbs, but I don't think I am going to get there.

I decided to take it for a drive, and it is running perfect from what I can tell. I can barely tell when it shifts it is so smooth, no slipping at all. Is 110 a deal breaker? Is it only a matter of time before it burns up? What would early symptoms look like? I took it back to the guy who rebuilt it (who will not remove or reinstall it that **** job is on me so trying to avoid it) he is going to put it on a lift next week and pressure test it himself, but if #1 and #2 are in spec, and I don't think there is anything else I can do to improve the 2nd and 1st gear pressures with just TV adjustments.

There seems to be a leak in the manual low circuit as 110 PSI is too low if that reading is at full TV, per my guide. Ask the trans builder if he installed a Sonnax o-ringed reverse boost valve (I think the ratio is .283) - the o-rings seal off an otherwise worn bore where manual low pressure can leak. Could also be worn manual valve bore in that location in the valve body but these are just guesses. Lastly, the TV cable may just need some fine-tuning (you may or may not have tried to adjust it).

 

[Broken85]

Thanks for these suggestions Nick. I have tried to adjust the TV cable to bring this up. Park/Neutral/Drive/3rd and Reverse pressures increase, but low and 2nd stay the same. This is allegedly a new valve body, so it should not be a worn bore, but anything is possible. I will follow up after he looks at it.

 

[Broken85]

There seems to be a leak in the manual low circuit as 110 PSI is too low if that reading is at full TV, per my guide. Ask the trans builder if he installed a Sonnax o-ringed reverse boost valve (I think the ratio is .283) - the o-rings seal off an otherwise worn bore where manual low pressure can leak. Could also be worn manual valve bore in that location in the valve body but these are just guesses. Lastly, the TV cable may just need some fine-tuning (you may or may not have tried to adjust it).

Finally got it back to the builder. Pan gasket was leaking anyway, so he had to drop it no matter what to fix that. I bought the Sonnax reverse boost valve you suggested and handed it to him. Worth the $30 so he had no excuse not to get it all done at the same time. Retested it, 1 and 2 are at 210psi which I think is now in spec per your sheet. Thanks for the help

 

[RetroC10Sport]

After a fluid change, I lost 4th gear. 1989 GMC, 1987 L98 TPI 350, 1991 Caprice 700r4. I did a fluid change 3 months ago, did not touch anything but the pan and filter. That day I had 4th before the change, I took it out the next day and noticed I only had 1st, 2nd and 3rd. I didn't use any RTV on the gasket. I used Mercon V fluid which is what i put in it when I put the trans in about 4 years ago. Fluid wasn't burned and there wasn't any crap in the pan when I changed it, it was just old.

I only use 4th maybe 3 times a year, otherwise it's just city driving and I leave it in 3rd for that. Should I adjust the TV cable again though I never touched it? What should I look for? Thanks y'all.

Finally got around to fixing this, missed driving this truck. The TCC solenoid had shorted out, replaced that and I have OD again.

 

[TDoc]

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Kept thinking I had a leak at the front of the pan. I took off the inspection cover, and the two lower bolts of the pump housing are slowly leaking transmission fluid. I double checked and it’s not the seal to the torque converter.

I started loosening the bolts and a bunch of transmission fluid came out.

Can I order just replacement seals / crush washers for the bolts?

Put RTV on the bolt threads?

 

[NickTransmissions]

You must be registered for see images attach

Kept thinking I had a leak at the front of the pan. I took off the inspection cover, and the two lower bolts of the pump housing are slowly leaking transmission fluid. I double checked and it’s not the seal to the torque converter.

I started loosening the bolts and a bunch of transmission fluid came out.

Can I order just replacement seals / crush washers for the bolts?

Put RTV on the bolt threads?

No RTV; just install new sealing washers. Also verify it's leaking from the bolts and not the pump o-ring (the o-ring seals the outer perimeter of the pump assy to the case).

I'm assuming you will be pulling the trans to reseal the pump? Or is there enough room between the bolts and front of the converter to pull those bolts all the way out?

 

[TDoc]

No RTV; just install new sealing washers. Also verify it's leaking from the bolts and not the pump o-ring (the o-ring seals the outer perimeter of the pump assy to the case).

I'm assuming you will be pulling the trans to reseal the pump? Or is there enough room between the bolts and front of the converter to pull those bolts all the way out?

It’s definitely the two lower bolts. They don’t have o-rings just a thin metal washer. Looks like I’d have to pull the trans to get the bolts all the way out. Maybe I’ll try some RTV around the outside bolt washer? It’s an odd leak. Sometimes no leak but guaranteed to leak when sitting for a few days.

I cleaned it really well and will leave the cover off a few days to triple check.

 

[NickTransmissions]

It’s definitely the two lower bolts. They don’t have o-rings just a thin metal washer. Looks like I’d have to pull the trans to get the bolts all the way out. Maybe I’ll try some RTV around the outside bolt washer? It’s an odd leak. Sometimes no leak but guaranteed to leak when sitting for a few days.

I cleaned it really well and will leave the cover off a few days to triple check.

No RTV; it wont work - as soon as you put some, trans fluid will contaminate it, rendering it useless. The o-ring im talking about goes around the entire pump housing. But sounds like the leak is coming from the bolt holes so new washer-seals should fix it.

 

[AuroraGirl]

It’s definitely the two lower bolts. They don’t have o-rings just a thin metal washer. Looks like I’d have to pull the trans to get the bolts all the way out. Maybe I’ll try some RTV around the outside bolt washer? It’s an odd leak. Sometimes no leak but guaranteed to leak when sitting for a few days.

I cleaned it really well and will leave the cover off a few days to triple check.

rtv is meant to create a gasket , but its not designed to do something like that. where you can get a proper o ring or gasket, normally you would want to use that. RTV has a place , but not there

Metal washer that are thin sound like crush washers

 

[RanchWelder]

I'm not certain a buna oil o-ring for oil will work?
You might have to try a silicone o-ring that's tight to the threads and seals when the bolt is tight to prevent the transmission fluid from eating a normal oil based oil ring? If I'm wrong please let me know, Nick?

RTV turns to mush as soon as sovant based oils, (such as transmission fluid), hit the RTV bonding surface.
Rubberized RTV will clog your solnoids, contaminate the Valve Body and pump valves WHEN it gets past the filter. (The filter's are not really as fine as they look).

Small specs of RTV can ruin the entire transmission.

Small silicone o-rings can be found on amazon and eBay in MM or SAE sizes for cheap. I personally own several hundred in various sizes for exactly such use.
If I'm not mistaken the small parts brand is where they come from on Amazon.

Buy a few sizes after measuring with a celiper and use them often when this issue arises in other leaks. Metric mm might be better for the steel gasket and the bolt dimensions?

2mm vs 3mm vs 4mm diameter o-ring makes it easy to measure for a tight fit. Buy in bulk so you have spares for other projects.

O-ring all the bolts under the case and be certain nothing leaks for years.
If you loosen one, it will be ruined, so have plenty standing by.

I use o-rings on the pump bolts and Red 3m sealant on the bolts so nothing leaks. You'll have to watch Richard's video's from TX on transmission rebuilds, in order to find the secret red 3m sealant

 

[jhealy748]

I tried to read through this thread to see if it has already been covered but dont see anything like I am experiencing. I have a 84 C10 and in 3rd it seems like the TC locks when I am in the gas far enough to accelerate but not far enough to kick down to the lower gear, but when I let off the gas some the TC unlocks almost like it is shifting down. The exact opposite of how I feel it should be. In reading some of the posts here, it seems like it may be a vacuum issue? Just not sure where to start and wondering if anyone else has had the same issue? @NickTransmissions

 

[idahovette]

You need to tag @NickTransmissions or @Matt69olds They know transmissions

 

[NickTransmissions]

I tried to read through this thread to see if it has already been covered but dont see anything like I am experiencing. I have a 84 C10 and in 3rd it seems like the TC locks when I am in the gas far enough to accelerate but not far enough to kick down to the lower gear, but when I let off the gas some the TC unlocks almost like it is shifting down. The exact opposite of how I feel it should be. In reading some of the posts here, it seems like it may be a vacuum issue? Just not sure where to start and wondering if anyone else has had the same issue? @NickTransmissions

Assuming you haven’t resolved or figured out the issue, check engine vacuum as well as the switches and harness on the valve body, assuming you are not using the mechanical TCC control valve train in the VB with the harness unplugged.

If you are using the mechanical TCC control valve train in the VB then check to see if the throttle valve, valve spring and/or C shift valve are stuck, sticking or broken (spring).

 

[NickTransmissions]

Bumping up the thread with a tear down of another half-assed 700r4 rebuild…I walk through all the issues with the previous builder’s work as well as cover inspection point and considerations for assembly…

700R4 Tear Down - Friday Afternoon Special

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Enjoy and thank you in advance for watching!