700r4 pressure woes

279 Views 8 Replies 5 Participants Last post by Limitless99, 8 d ago

Limitless99

Discussion Starter · 12 d ago

Well I took my time and rebuild my 90-91 700-r4. Still realized I made an error. There was a scratch where the pump rotor rides in the pump barely catch nail but I lightly sanded it out. Used a flat sand but didn't set no pump clearance. I used a straight edge to check and thought I would be fine.

Pre rebuild it seemed to have ok pressure but I was using hanyes manual and not the ASTG at the time. So i didnt test MAX tv pre-rebuild. Min TV pressure was in spec pre rebuild. So I thought if its not broke don't fix it. So it's still 10 vane and there was no visible damage to vanes.

After rebuild
COMPLAINT : MAX TV pressure readings are low when at operating temperature after driving not that long. It also shifts1-2 and 2-3 a bit later like 1800rpm light throttle, that could just be the shift kit I guess. I did also change a governor spring per trango instructions for the v6 governor weights, that's what was in there. But I think gov is only affecting wot shifts? The operating temp line pressure in 2nd is 80psi @ wot and shifts to third pressure goes to 140 as it shifts and holds that pressure.

Here is cold and operating temp pressures.

All I did to the pump was seals and added .471 boost valve. Grind down the PV valve land and plugged a hole in the pump per transgo instructions. I should've just replaced pump with the nick.

It does appear to shift ok. It doesn't slip or anything but im worried about durability.

solution?
I don't know if I should try taking the easy way out and change to .500 boost valve and .296 reverse boost valve? Don't know numericly what kind of pressure increase I could expect from them? Or just pull this trans back out and replace the pump without wasting anymore time?

Attached is pic from my latest pressure test. It has pretty good pressure cold but one it warms up it drops substantially. ASTG manual doesn't say if the readings are taken operating temp or not? Hanyes values are lower but specify at operation temp.

Some rebuild information in case needed:

used the solid teflon seals on stator and input shaft
Installed SK700 full shift kit from transgo
new transgo separator plate
raybestos clutches and kolene steels
the beast sunshell
Upgraded to molded pistons in 3-4
pinless accumulator 3-4
Added 3/4 load release springs

Any input much appreciated. I'd rather not pull it back out but I will if no better option. Thanks.

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blwn31

· #2 · 12 d ago

Column E "ATSAG Max Spec Temp", you should have "ATSG Max Spec Press" not temp. If your temp is 320, it's toast.
I'm no expert here, but I highly doubt that a little scratch is gonna drop your pressures that much unless you sanded and river channel in it. I'm more in the camp the pump halves are not flat and you have a cross passage leak. Once you split the pump halves a light flat stoning is in order to return the pump faces to flat. Then recheck your vane clearances to make sure your not to tight. I bet if you pulled the pump and split the halves and bolted it back together you would get different readings again.

Keith

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Crosley

· #3 · 12 d ago

the hot , max TV pressure reading is telling me the line bias valve may be opening. Which spring was installed there from the kit? Red spring should used or actually better is to block that line bias valve with a piece of welding road or similar steel rod so it does not move. Keep spring in place to retain tension on the valve

Does this trans have dual springs on the pump slide ? Was the pump slide pivot pin replaced or checked for wear? The pin usually wears on one side

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'49 Ford Coupe

· #4 · 12 d ago (Edited)

When I put the Sonnax .50 pressure valve in, it made a significant difference... you can do it without pulling the transmission. Just pull the pan, make a little holding tool to get the snap ring to cooperate, and long skinny snap ring pliers.. also there are videos of pressure tests ...See my website here on the subject, one of hundreds...

As for the governor, the TV valve position varies the pressure that loads against the governor weight/spring forces to adjust the shift points at all speeds, not just WOT..

The 700R4 Transmission, Chapter 2 - 49FordCoupe

Check out how to build a classic 1949 Ford street rod with modern features and power and convenience you never thought possible. With a 383 SBC Stroker engine, S-10 front frame, Jaguar XJS/XJ6 rear end, air conditioned, power brakes, and power steering.

49fordcoupe.smugmug.com

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Limitless99

Discussion Starter · #5 · 11 d ago

Thanks all. I did not flat sand the pump halves. And yeah putting max temp in that column is typo.

Crosley
I used a purple spring in line bias valve. I believe it's the same as red but that's strange there colors are different. I used the SK700 full shift kit not the 700jr.. my trans had a missing MTV up spring, that's the only reason I bought the full kit, to get that missing spring. I have instructions for both kits. I could lock that like you suggested with a welding rod.

The Last rebuild was done less than 10k miles ago by a shop. Though it's almost 10 years old now. I didn't use lockup at time and had a custom bracket for tv cable. Needless to say I burnt it up. But there was no wear I can tell in the pump pivit pin had nothing. Just that nick where the pump rotor sits. It does have the dual pump slide springs.

49ford
Thanks for the info i will check out the videos. I don't feel like the TV is affecting the shifts quite like it did before. Maybe I got something going on with that.

I noticed yesterday that it also doesn't upshift at a coast. Normally I can let of the gas and it would upshift to next gear with no load. It stays in gear until to throttle to the next gear. That's hard to explain but saying I was coasting downhill. I feel like it needs throttle to upshift. Even if the rpms are up there a little. Like 1800.

Thanks all for the help. Much appreciated

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BogiesAnnex1

· #6 · 11 d ago

A common problem with the 700R4 through the late 90’s 4L60E is the pump housing warps allowing a leak from the high pressure output into the vent system, a telltale sign is blowing ATF out the vent hose.

The TV cable is very critical as it is modulation as well as kick down you need to follow this to the letter.

https://cpttransmission.com/tech_tvcable.htm

You need ASTG manual.

You made a lot of changes it can get complicated to sort out.

Bogie

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Limitless99

Discussion Starter · #7 · 8 d ago

BogiesAnnex1 said:
A common problem with the 700R4 through the late 90’s 4L60E is the pump housing warps allowing a leak from the high pressure output into the vent system, a telltale sign is blowing ATF out the vent hose.

The TV cable is very critical as it is modulation as well as kick down you need to follow this to the letter.

https://cpttransmission.com/tech_tvcable.htm

You need ASTG manual.

You made a lot of changes it can get complicated to sort out.

Bogie

Thanks for the input. No atf out the vent thankfully. It does shift good. And the pressure improved. I bought .5 boost and .283 Rev to increase it some. I'm wondering If something was sticking from too much assy lube or a seal mightve been twisted. All is perfect except no 2-1 downshift. I'm hoping once I increase pressure it fixes that.

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BogiesAnnex1

· #8 · 8 d ago

I presume you mean no automatic downshift?

Red this:

Gears Magazine - A Look Back: Adjusting the THM700-R4 Throttle Valve Cable

The 700R4 has been around for over 30 years, and yet they still show up in shops all across the country. For veteran builders this unit is pretty straightforward, but for the new guys who are thinking, “where’s the computer?” some issues might pose a problem. Step 1: With the engine off...

gearsmagazine.com

Bogie

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Limitless99

Discussion Starter · #9 · 8 d ago

Yes, automatic 2-1 downshift. The rest of downshift's work except 2-1. Some say it should also do a 3-1 downshift. It doesn't do 3-1 either. It's a gm reman trans so exact year is unknown. But using other items to date it I believe it's a 1990 or 1991 model 700r4.

Thanks for the article. That's different then the one I used from transgo. I shouldve mentioned i purchased the bigger boost and rev valves but didnt install them yet. Soon as I install the new boost and Rev boost. I will set TV just like that article you shared. All though I might try that before I make the pressure changes by just to see. I think more pressure would be good. I was very conservative drilling the separator plate so shifts could use a little more firmness.

Thanks again for the input.

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