700R4 Information Thread

[NickTransmissions]

My reverse input drum is the second style with the round feed hole.

I have identified the problem!

Next step is placing that drum into the scrap bin and purchasing a new AC Delco rev input drum. Your current belleville plate, piston, return spring and clutch pack w/backing plate will all transfer over. That should solve your clearance problems and enable you to install an Alto wide red band vs the stock band.

Also, verify you dont have first design rev input clutches - those were thicker than all of the subsequent clutch designs and used a waved plate instead of a belleville plate. They were only found in the first design drums w/the steel piston.

 

[EvilGenius]

I have identified the problem!

Next step is placing that drum into the scrap bin and purchasing a new AC Delco rev input drum. Your current belleville plate, piston, return spring and clutch pack w/backing plate will all transfer over. That should solve your clearance problems and enable you to install an Alto wide red band vs the stock band.

Also, verify you dont have first design rev input clutches - those were thicker than all of the subsequent clutch designs and used a waved plate instead of a belleville plate. They were only found in the first design drums w/the steel piston.

I was hoping to avoid buying a new drum as this one wasn't warped noticeably and wasn't the cursed first design. Also I already have a replacement band, whichever comes in this kit here.

My old (and new) frictions measure out to .07. I have the aluminum piston.

Would you still say that my only real option is to get a new reverse input drum?

 

[NickTransmissions]

I was hoping to avoid buying a new drum as this one wasn't warped noticeably and wasn't the cursed first design. Also I already have a replacement band, whichever comes in this kit here.

My old (and new) frictions measure out to .07. I have the aluminum piston.

Would you still say that my only real option is to get a new reverse input drum?

You need at least .040 to be on the safe side so get it however you need to get it. Your existing drum is prob warped but even if it's not, it's an inferior design. Those drums also had a lot of variability; I have had issues with them and clearance as well in the past. You can machine a step into the backing plate on the snap ring side, if necessary but Ive never elected to do it.

I also never reuse them - all my 700R4s get a new rev input drum, wide band and vette servo. It's good practice to update those three things for longevity and reliability.

 

[EvilGenius]

You need at least .040 to be on the safe side so get it however you need to get it. Your existing drum is prob warped but even if it's not, it's an inferior design. Those drums also had a lot of variability; I have had issues with them and clearance as well in the past. You can machine a step into the backing plate on the snap ring side, if necessary but Ive never elected to do it.

I also never reuse them - all my 700R4s get a new rev input drum, wide band and vette servo. It's good practice to update those three things for longevity and reliability.

Thanks for the really fast responses! I'll have to pick up a new drum I guess.

 

[HotRodPC]

Love you man.

Love you too Dawg !!! One of these days I hope to get that way. I got some people that way I want to see. Life been suckin worse than normal lately. Parents getting old and requiring a lot of my time taking care of them along with my all my own ailments.

 

[NickTransmissions]

Hey All, bumping up the thread with a video on the "Nemesis" Rebuild profile ... This will be the first in a series of vids capturing the build-up...I'll post here as each gets published to my YT channel. Enjoy and TIA for watching!

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[NickTransmissions]

Bumping this up with another video - this one showing the pump repair/ream job and installation/testing of the Sonnax oversized pressure regulator valve...The original valve was heavily worn and likely contributed to the myriad of drivability symptoms that plagued this unit while it was in the truck.

Enjoy and thank you so much for watching!

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[Scott91370]

What kind of power can a factory and a built 700r4 hold?

@NickTransmissions - This one is for you.

 

[Daddiotx]

Hey Nick, have a fresh rebuilt (by me) and do not have a 3-4 upshift. Read all of the previous comments, hopefully I have all the info. It's really a stock application, with all of your upgrades from the video series.

Thanks!

Pressure test: 1000rpm, no TV/Full TV, brake on, numbers may be low, one spot on gauge with known air was 10-20lbs low.
P 100/190
R 130/250
N 70/190
4th 90/200
3rd 90/200
2nd 120/120
1st 120/120

On stands, trans shifts 1-3 at 'normal' mph, however 3rd never sees a pressure rise above 90lbs, never shifts to 4th. Manual shift through gears, 4th never appears.

your suggested causes from above:
- Worn pump, boost valve, pressure regulator valve or working surfaces - purchased reman pump, hope it's good, 0.5" pr valve
- 3-4 relay valve installed backwards - just checked, it's correct
- Worn/sticking TV boost valve - new 700jr shift kit, and see pressure rise/drop with TV actuation
- Worn, leaky TV plunger and/or sleeve - maybe?
- Worn or excessive clearance in 3-4 clutch - New steel/clutch pack, ~0.050" clearance
- Worn or torn teflon sealing ring in the 4th gear servo apply piston just inside the cover - Did not install gold spacer from kit, New Alto max band and new reverse input drum
- Worn or torn rubber o-ring style seal on the 4th accumulator piston - Used your performance tip on piston, bottom piston no seal legs up, top piston legs down, no spring
- Misplaced or missing check balls - verifying
- Bad valve body (no pin-pointable cause or causes) - hope not, bench buddied all holes, checked for free motion.

 

[idahovette]

Scott, you need to tag Nick @NickTransmissions for him to see your ?????

 

[Daddiotx]

Hey @NickTransmissions, will try this again with the tag (Thanks Perry!)

I have a fresh rebuilt (by me) '89 700r4 and do not have a 3-4 upshift. Read all of the previous comments, hopefully I have all the info for you to help out. It's a stock application, with all of your upgrades from the video series. Hoping you have some insight on what to look at next.

Thanks!

Pressure test: 1000rpm, no TV/Full TV, brake on, numbers may be low, one spot on gauge with known air was 10-20lbs low.
P 100/190
R 130/250
N 70/190
4th 90/200
3rd 90/200
2nd 120/120
1st 120/120

On stands, trans shifts 1-3 at 'normal' mph, however 3rd never sees a pressure rise above 90lbs, never shifts to 4th. Manual shift through gears, 4th never appears.

your suggested causes from above:
- Worn pump, boost valve, pressure regulator valve or working surfaces - purchased reman pump, hope it's good, 0.5" pr valve
- 3-4 relay valve installed backwards - just checked, it's correct
- Worn/sticking TV boost valve - new 700jr shift kit, and see pressure rise/drop with TV actuation
- Worn, leaky TV plunger and/or sleeve - maybe?
- Worn or excessive clearance in 3-4 clutch - New steel/clutch pack, ~0.050" clearance
- Worn or torn teflon sealing ring in the 4th gear servo apply piston just inside the cover - Did not install gold spacer from kit, New Alto max band and new reverse input drum
- Worn or torn rubber o-ring style seal on the 4th accumulator piston - Used your performance tip on piston, bottom piston no seal legs up, top piston legs down, no spring
- Misplaced or missing check balls - verifying, 4 balls case side plus low reverse, 2 vb side plus large 5/16"
- Bad valve body (no pin-pointable cause or causes) - hope not, bench buddied all holes, checked for free motion.

 

[NickTransmissions]

Hey @NickTransmissions, will try this again with the tag (Thanks Perry!)

I have a fresh rebuilt (by me) '89 700r4 and do not have a 3-4 upshift. Read all of the previous comments, hopefully I have all the info for you to help out. It's a stock application, with all of your upgrades from the video series. Hoping you have some insight on what to look at next.

Thanks!

Pressure test: 1000rpm, no TV/Full TV, brake on, numbers may be low, one spot on gauge with known air was 10-20lbs low.
P 100/190
R 130/250
N 70/190
4th 90/200
3rd 90/200
2nd 120/120
1st 120/120

On stands, trans shifts 1-3 at 'normal' mph, however 3rd never sees a pressure rise above 90lbs, never shifts to 4th. Manual shift through gears, 4th never appears.

your suggested causes from above:
- Worn pump, boost valve, pressure regulator valve or working surfaces - purchased reman pump, hope it's good, 0.5" pr valve
- 3-4 relay valve installed backwards - just checked, it's correct
- Worn/sticking TV boost valve - new 700jr shift kit, and see pressure rise/drop with TV actuation
- Worn, leaky TV plunger and/or sleeve - maybe?
- Worn or excessive clearance in 3-4 clutch - New steel/clutch pack, ~0.050" clearance
- Worn or torn teflon sealing ring in the 4th gear servo apply piston just inside the cover - Did not install gold spacer from kit, New Alto max band and new reverse input drum
- Worn or torn rubber o-ring style seal on the 4th accumulator piston - Used your performance tip on piston, bottom piston no seal legs up, top piston legs down, no spring
- Misplaced or missing check balls - verifying, 4 balls case side plus low reverse, 2 vb side plus large 5/16"
- Bad valve body (no pin-pointable cause or causes) - hope not, bench buddied all holes, checked for free motion.

To be clear, you have NO 3-4 upshift?

If so, check the 4th gear servo piston's scarf cut sealing ring - it's on the inside of the servo cover. If that's in good shape, drop the pan, VB and see if any valves are sticking (3-4 throttle valve/spring/sleeve and 3-4 shift valve, 3-4 relay valve, etc).

Your TV pressures at MinTV are a bit elevated but not likely causing a no-fourth upshift condition...Your TV plunger and sleeve seem to be healthy based on the line pressure readings at full TV above. Governor is a possibility as is the governor bore in the case.

I suspect valve body but won't know until if/when you swap another one in there and see what happens.

 

[Daddiotx]

@NickTransmissions Thanks for the reply. Yes, no 3-4 upshift.

Valve body is already down, wanted to check 3-4 shift relay. Will go through again and verify everything is right/clear. I don't really trust this vb, had issues with it in another unknown trans. Will check servo, but am not optimistic. If don't see anything, will swap in another vb. Will report back.

Thanks for the sanity check!

 

[NickTransmissions]

@NickTransmissions Thanks for the reply. Yes, no 3-4 upshift.

Valve body is already down, wanted to check 3-4 shift relay. Will go through again and verify everything is right/clear. I don't really trust this vb, had issues with it in another unknown trans. Will check servo, but am not optimistic. If don't see anything, will swap in another vb. Will report back.

Thanks for the sanity check!

You're welcome, man...Sometimes the valve body is no good but there's no clearly identifiable reason...I am working on designing a vacuum test plate for those 700R4 VBs so that they can be thoroughly tested and weaknesses identified before bolting them back on...

 

[Daddiotx]

@NickTransmissions - Update: Checked 4th servo, everything was as supposed to be. Pulled non-4th vb, compared each valve with a know working vb, everything similar. So, swapped to the known working vb, now have 4th, yay! Pressures seem close the same, more bounce in the gauge, not sure what that's about. Much happier. Now chasing a lockup issue - I know I put the o-ring on the input nose, and I verified voltage through the pressure switch. It's a summit lockup kit, need to talk to them about how that switch works, it seems to be variable resistance, not on/off like I would expect.

So, might be in the market for that vb test plate! Or, just send this one in for a core and be done with it.

Thanks for the kind words and help. Got me through on this one.