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700R4 lost 3rd gear

7K views 45 replies 4 participants last post by  ASE Doc 
#1 ·
Hi everyone, Before I dig into this unit, I'm posting a brief explanation of what's been done to it and what happened this weekend, in case anyone has thoughts on it. The trans lost 3rd gear about 3-4 years ago. The 2-3 shift was getting softer and I could tell it was slipping before it finally failed. I found the 3-4 clutch pack burned up and shot. I rebuilt it going to great lengths to make the 3-4 clutch as strong as possible. This includes using the pricey Sonnax input housing with the bolt on 3-4 backing plate. I also installed the pieces to maximize 3-4 clutch capacity. I installed an 8 stack of thick BW hi energy green clutches and thick steels.

The rest of the unit was replaced with new high test parts like a billet 2nd servo and Sonnax dual piston 4th servo. A new pump and Transgo 2-3 shift kit with some added pieces from Sonnax. I installed the unit with an Edge 3,500 10" converter. After the build, line pressure at 3,500 in 3rd gear was 285psi.

One weird thing that happened with this 3rd gear failure was the speedo had stopped working last week. I checked the cable and was going to check the drive gear to be sure it was turning before swapping a new cable in. Then, right at the same time 3rd gear left me, the speedo started working again. I'm suspicious of the drive gear retainer, that it may have come loose and gotten into the governor gear and locked it up.

I'll get the car into the shop later this week and check things out. A pressure test should tell me if this is a hydraulic issue. I'll pull the tail housing and check out the gov gear. The 3-4 clutch is tough to air test but I'll see what I can come up with. If anyone has any thoughts on this issue, post a reply. I'll take all ideas into account when I do the check out. Maybe the trans will be coming out again. Oh well, it's about due for a fluid change anyway.
 
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#29 ·
Trust me, I have issues [emoji2]
Too much of something. Most likely pressure. Dean Mason valve, RatioTex springs, .... ???
Light throttle 1-2 is 2k, 2-3 & 3-4 are 4k
WOT in 1st hits my 6k rev limiter.
Sonnax 117 governor.
I won't get into the fuel injection problems [emoji2]

Sent from my SM-G920P using Tapatalk
 
#30 ·
You say that your WOT 2-3 shift is at 5,500. That would tell me that the governor is set up okay. The problem then would likely be the TV/line pressure curve. The rise is too quick off idle, or just too high even at idle.

I remember the Dean Mason valve and that the decrease land is different so that it will hold higher line pressure with less MTV pressure. Looks like it was meant to be a stand alone solution to low line pressure. I would expect that used with the Sonnax .500 and .296 boost valves, which along with the rest of the Sonnax line boost kit were also a solution to low line pressure, and the Ratio tech springs which were another solution to low line pressure(you see where this is going), I would imagine you have very high line pressure right off idle. Maybe high even at idle.

I shimmed the Sonnax TV spring and added a TV spring blocker of the same dimensions as the TG piece, all to increase base line pressure to just over 100psi. I ended up around 110 at idle. This was intended to prevent any slipping of the 3-4 clutch at light throttle cruise. Of course my trans won't shift out of 2nd below 30mph anyway, has been this way since the build 15 years ago. Probably has to do with the vette governor they put in.

I was told by Crosley and Dana that 89psi at idle is plenty, but you know how it is. My line pressure from idle rises to 285 by 4K rpm. I don't remember if I had it fully warm at that point but with my coolers, it never gets very warm anyway. With my TV/ line pressure curve set up this way, the unit shifts very well. I did have to remove one coil from the 1-2 shift valve spring to get the 1-2 shift down closer to the same revs as the 2-3 shift.

I would definitely connect a pressure gauge and see where you are. Consider swapping the dean mason valve out for a stock style valve with the Sonnax line boost kit. I like the Ratio Tech TV spring booster(the stiff yellow one that goes inside the TV spring). It's the same length as the blocker I made for mine. I've thought about trying it in place of my blocker, you might consider that for yours. I also like the Ratio Tech dual PR valve springs. I would consider using either the two springs together or the inner spring with the Sonnax spring.

I have the TCI blue(may be purple)PR spring in mine. This spring along with their .571 and .400 boost valves produces 300psi line pressure for those who just can't get enough. With the Sonnax boost valves and my TV spring blocker it gets me my 285psi.
 
#31 ·
I suppose since I mentioned cutting a coil off the 1-2 shift valve spring, I should also talk about how I arrived at that conclusion. After the last build, with the TV and PR valves set up the way they are, I had a great 2-3 shift but 1-2 would barely shift at the 6,900 rev limiter. I talked to a local guy, Ken at Oregon Torque Converter, who builds the front pump that I have. He said that to tailor just one shift point. I should work with the shift valve spring tension. This makes sense to me as the spring is what determines the overall balance between line pressure and governor at each shift valve train.

Ken recommended a scale, I bought a cheap kitchen scale from Fred Meyer so that I could measure the tension of the 1-2 shift valve spring. As Ken said, it's not the accuracy of the measurement that counts as much as establishing a base line for comparison. I wanted to bring the shift point down by about 1,400 rpm or about 20%. So, I measured the springs working travel in the valve at 7.5 lbs from extended to compressed. Then I trimmed it down til I achieved 6 lbs over the same travel range. That did the trick. The trans has shifted great from 1st to 2nd since then.

Anyway, that's what worked for me.
 
#32 ·
There again I'm not positive, if I was a full throttle. According to my data log it was only 90% but then I found out my map sensor needs replaced.
I'm hooking the gauge up this weekend. Crossing my fingers that it's not a stuck pump slide because I forgot to check the clearance a 2nd time, after flat sanding, after I noticed the reman pump half was not completely flat.

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#33 ·
It's hard to imagine the pump slide sticking against 280+psi. It seems more likely that it would stick in the decrease position, against the slide spring. I assume you're using the heavy duty single spring, like the one Sonnax sells. That will help force the slide back to the full output position.

The pressure gauge will tell you if in-fact the slide is stuck at full output, or if anything else is causing the pump to hit max pressure. The pressure relief valve opens at 300psi. If you are hitting 300psi, either the slide is stuck or you have a combination of boost valves, TV pressure, and PR valve that is forcing the pressure this high. I suspect the dean mason valve, used with the other pressure boosting measures, as the chief culprit.

Once you have verified line pressure and the line pressure curve, then you can decide where to go from there.
 
#34 ·
I'm happy my 3rd accumulator check valves just got here from Summit Racing. Summit doesn't list alot of trans parts, but they have good pricing on what they do offer. I had to wait a while for these AC Delco check valves but they were half the price of other suppliers and fortunately, I'm not in a big hurry.

Getting close to having everything here for the repair. I expect the extreme servo from BET by the end of the week. Also ordered their input shaft seal resizer.
 
#35 ·
The extreme servo arrived from BET Performance yesterday. Talk about quick service. I chose the snail mail shipping option too. I also got their input shaft sealing ring resizer. It's machined from steel and very well made, excellent finish so it won't tear up the teflon. It's a very nice tool at a great price.

They sent me an extra tool, a manual shaft seal installer, that I didn't order and they didn't charge me for. I figure it must be by mistake. Of course I left my cell phone at home today so I can't phone them to let them know about it. I'll call them tomorrow. These are great people and I'm not going to take advantage of them.

Of course without my phone, I can't take a photo of this great servo either to post up here. The dimensions and finish on this thing are just perfect. I cant' wait to run it. I'll get photos tomorrow for everyone to check out.
 
#37 ·
Just spoke with Dana at Pro Built Automatics on Monday. He was sending out my parts order on Tuesday. Once that's here, I'll have everything I need to go back into this unit. I still may not do the repair until late spring. It depends on work and finances. Part of putting the car up for the winter is the savings on insurance. Things are especially tight this winter so we'll just see how it goes.

Work right now is especially interesting(the kindest term I can think of for it). I am doing a 2.8L Cologne V6 in a 1978 Pinto Runabout. It the bay next to the Pinto is a 1982 Delorean DMC12. Spent my afternoon and evening yesterday on a Jaguar X-Type.

It just keeps gettin' better and better.
 
#38 ·
Hi again everyone. I've got all my 700R4 parts now. Still no closer to setting a time to do the work. I'll see how things look as we move towards spring. I wanted to post a photo of this tool I picked up from BET Performance. You transmission guys will probably recognize it as a turbine shaft sealing ring resizer for the 700R4. It fits others as well with the same size input shaft. This one is machined from steel and the finish is very fine so it should work well on the teflon rings. BET sells this tool for $33. I don't remember what the Kent Moore tool sells for but I don't think it's this cheap. Anyone looking to overhaul a 700R4 should own this tool.

BET also makes a seal expander to go with their resizer. It's not like the Kent Moore tool, which actually allows you to slide each sealing ring right into place. The BET tool just stretches the ring so that you can slide it over the shaft. It also sells for $33. I'm going to pick one up and see how it works on one of the extra sealing rings and an old input shaft I have on hand. I'll post back with my impression of it. If it works anywhere near as well as their resizer, that will be great.
 
#40 ·
Reviving this thread as I finally got the trans out and on the bench this past weekend. It was in fair shape all around. A little more friction material from the 3-4 clutches than I was hoping for. I had a new 2-4 band, overrun and forward clutch sets on hand just in case but those in the unit were in great shape so I reused them. The pump, which was new 3 years ago had some scoring on the face. The housing was in good shape so I used 60 grit sandpaper glued to a sheet of steel and laid on the concrete floor to surface the face until the scoring was gone. Then I worked my way up to 600 grit to make it smooth.

I removed the Transgo high rev springs from the 3-4 and forward clutches and replaced them with stock. I installed the Sonnax 3-4 boost springs that come with the Smart Tech housing. I removed the Transgo orifice and installed a new AC Delco checkball in its place. I set 3-4 clutch clearance at .043. Is that a little too tight?

I kept the Superior 2nd servo and relieved the back of the separator piston to clear the washer on the Sonnax 4th servo. I installed the TH400 intermediate servo spring. I also replaced the 3rd accumulator checkball. I would say that the 2-3 shift feels much better now.

I have a new problem though since the work this weekend. 1st through 3rd all seem fine, but as 4th gear starts to engage, it feels like the brakes are being applied. It almost has to be the overrun clutches being engaged even though the trans is in D. Also, when I got back from the road test, I at first didn't have reverse. I had to shift into park before whatever was stuck freed up. I have some thoughts on what I might have gotten wrong. I'm hoping for some input on what I should look at first.

The input housing went together very nice. I also installed new input shaft sealing rings using the BET seal resizer. I don't suppose the problem is there. I set input shaft end play a little tight maybe. I have all torrington bearings throughout and I set end play at .010". Is that too tight? Could that be causing things the tighten up once they get warm? I noticed today after a short road test, the fluid was hot. Before this weekend, I could drive the car for miles and the fluid would just be warm.

One concern is that I didn't get the pump face flat enough. I even had a straightedge right there but didn't check it before I pressed the stator support back in and assembled the pump. I can definitely see cross leaks at the pump causing problems.

Any thoughts?
 
#41 ·
Talking to Crosley, I think I can officially state that I am a dumb*ss.

Certainly figured out the binding in 4th. Would think that I would remember the PITA of installing the forward clutch piston over the reinforcement ring. The ring prevents you using the inner lip seal installer. You have to use some other means of shoehorning the inner lip seal of the forward piston over the hub. I have cussed that part of the assembly enough times I should have realized it was conspicuously missing from this weekend's exercise. I will call it an exercise because I will be doing the job a second time.

My screw up on the pump was not using a lathe to surface the stator side. I'm sure I got it out of true and not flat. Worse yet, the person who did the pump I have now no longer does them. The only pump I can find locally is used. I'm seriously considering taking this pump stator, if it's not completely wasted now, into the machine shop and turned on the lathe. Another option would be to get a used stator and have it surfaced. Mine might be getting a little thin from me sanding it down . I've got someone at the hard parts supplier in Portland looking for a good core. If he finds a smooth one, I can just put new bushings in it and use it as is I guess.

Man, I had thought this job through so many times over the winter just to drop the ball big time. I think maybe I'll just pull the trans and have my buddy flat bed the car back to my garage at home. Then I can take my time and go through the unit again, replacing anything that got hurt. The fluid, still bright pink, smells pretty burnt. I may also send my converter over to Kent at Oregon Torque Converter. Have him cut it open, clean and inspect it. I'll also be sure I have a good pump ready to go in. Good thing I have those new frictions on hand. Pretty sure I'll need them now. I only hope the great 3-4 stack up I put together wasn't hurt. They were engaging really well. I'll inspect them when I tear it down.

More to come soon in this saga of my stupidity. Oh well no better lesson than experience right? I'm sure the upcoming build will be awesome!:D
 
#42 ·
A standard lathe will cut the surface of the stator support (pump cover).

Chuck it up in the jaws.. with a live center on the splined end of the support. Critical part is the angle & curve of the cutting tool to avoid chatter and not creating a vinyl record effect on the surface of the aluminum.

Flat sand the pump body on something flat with 180 grit paper or finer, wet is better. Solvent, WD-40 or similar on the paper
 
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#43 ·
Thank you again Crosley.

I see now that the pump cover has to be aligned precisely to the stator support, duh. There are a couple of machine shops in the area that could lathe cut the pump cover. I'm thinking I probably sanded about .010 off it. That and I'm sure I got it out of true. How much more can be taken off before it starts to affect operation? I am looking for a good used cover to replace this one. We'll see how badly the pump body and parts were damaged in 20 miles of driving.

I understand now why I had the issue in 4th. I'm not as sure why the unit got so hot. I hope it wasn't because of misalignment between the stator support and pump. My greatest concern is for the torque converter and the input housing. I am thinking that I must have had clutches dragging due to cross leaks. The forward clutches would be engaged anyway in any gear but reverse, the overruns are engaged normally in 1-3. The shifting seemed pretty normal around town. However, the unit was getting hot immediately.

I'm sure I'll know more once I get it torn down again. I'll up date this thread at that point.
 
#44 ·
Thought I should update this thread since going back into the unit last weekend. I found a good rebuilt pump. Basically, a good used 732 case with new rotor, slide and vanes. I swapped in the heavy(Sonnax) slide spring, after inspecting and re-cleaning the pump. I also swapped in the big boost valves from the previous pump. The pump came with the TH350(wider than the 700R4 bushing) front support bushing, a new teflon pump bushing, and I installed the wide teflon rear bushing.

I kept the pump that came out. No scoring damage from running it after the sanding job. The body is still in great shape. In fact, the pump only has about 6Kmi on it since a fresh rebuild. The only issue was a small scored area on the cover, probably from digesting friction material. I'll have it trued up in a lathe and save it as a spare.

Otherwise, I found where I'd left out the forward piston inner lip seal, just like Crosley said. Air testing the housing is really a good idea to save yourself this kind of headache. I seriously dropped the ball two weeks ago on this thing. This time around everything went great. I tore it all down to the bare case, washed all the parts, they were well coated in friction material from the wasted OR clutches. The other clutches all still looked just as good as they did two weeks ago. Even the forwards, which live right next door to the ORs, were in great shape.

I reassembled the unit using all the same clutches, aside from the OR and forward which I replaced with new. I washed the 3-4 frictions, brand new two weeks ago, in clean ATF and washed the 3-4 steels with the rest of the parts. After assembly, this time including the forward piston inner lip seal, I air tested the housing and it tested fine. I reused the teflon turbine shaft sealing rings since they're still brand new from two weeks ago.

As I think I said in an earlier post, the $32 turbine shaft sealing ring resizer from BET performance worked great. I used a funnel to spread the rings for installation.

One change I made in the reassembly was swapping in the Sonnax 2nd servo in place of the Superior. I feel like the change really did clean up the 2-3 shift. The 1-2 shift is still nice and firm under any throttle and mild at low speed light throttle. The change from the more firm Superior will take some getting used to but since the whole servo assembly seems to work better now, I'll keep things as they are. I installed the high rat cushion springs from the Ratio Tech kit along with the factory cushion spring and drilled vents in the steel cover. I used the stiffer TH400 intermediate servo spring in place of the factory spring. Using the Sonnx 2nd servo, I was able to install a 4th servo return spring. I already had the Sonnax 4th servo installed. Now I have the whole set.

One issue I found during the teardown is damage to the lugs of the Sonnax Smart Tech apply plate and to the tips of the apply ring legs. The damage appears to be from the apply plate coming off the ring and floating loose in the housing. I'm afraid the legs of the ring might even be spreading from g-force at high revs and passing by the lugs. Talk about centrifugal apply of the 3-4 clutch. I'm betting this has alot to do with the failure after just 6Kmi of what should be a very tough clutch stack.

The apply plate and backing plate have been hot spotted since the first 3-4 clutch failure but I've let that go. One thing I noticed after the first failure was that the apply plate had come off the legs of the apply ring and floated loose in the housing. No damage to anything else, just a rub mark on the inside of the plate from the input ring gear. No visible scoring to the gear. No damage noted to the lugs or the apply ring legs. I put things back together that time(3 years ago) and continued to run the housing without the boost springs in the 3-4 clutch. I was told to do this when using the CS-7 transgo springs.

I've talked to the trans expert who told me to leave the springs out, a good friend of mine for whom I have great respect, about the damage to the apply plate and ring. He was surprised by the news. I promised him photos once I have the parts out.

I believe the difference here is the Sonnax design of the plate. I remember noticing how much shallower the lugs of the Sonnax plate are than those of the factory style plate. I'm referring of course to the late style apply plate that goes directly onto the legs of the apply ring with no retainer between. The factory plate has deep enough lugs that the apply ring legs probably couldn't get past them, even in the event of a 3-4 meltdown. The Sonnax apply plate lugs are only maybe 1/8"-3/16" deep. Not much material there to keep the legs back without the boost springs keeping things firmly in place.

At the time last weekend I decided to reassemble with the boost springs and let the damage go. Since then, I've had second thoughts. The replacement parts are on the way. Sonnax sells a service kit for the Smart Tech, great price at just $100 and change, considering they could charge whatever they want for it. I got a fresh "7" apply ring from my friends at Perfection Plus hard parts(short legs for thicker steels on the factory heavy duty unit makes more space for the 3-4 clutch stack). Dana at Pro Built is sending me another 8 friction 3-4 clutch stack. The Smart Tech housing with the "7" apply ring has 1.25" inch 3-4 clutch capacity. That's with a no flex bolt on backing plate and a super rigid apply plate. Very cool.

I forgot to ask Sonnax tech, when I called about the repair kit, why they don't make those lugs deeper. There's plenty of room on the outside of the apply ring legs. You could make those lugs as deep as you want. Maybe they are thinking of rotating mass. Either way, they really really mean for you to use their long boost springs in the 3-4 stack, and I guess now I know why. For anyone planning to use this bad*ss input housing, learn from my mistake and DO NOT leave those springs out.

On this last weekend's build up, I went with the factory 3-4 and forward spring packs, making sure all the springs were in tact(none broken), and installed the boost springs. Those Sonnax springs are pretty stiff. I'm thinking they go a long way towards bridging the difference between the factory spring packs and the TG CS-7 springs. Crosley says he mixes the stock springs and TG CS-7 springs and uses the boost springs. I still have the TG springs incase I decide I want to do that down the road. I may also step up to a 9 stack next time, just for the heck of it.

I also yanked the TG orifice and installed a brand new AC Delco check ball. Two weeks ago, I replaced the 3rd accumulator check ball capsule. When I have a phone again, I'll post a photo of the cool tool I made from a 5/16" grade 8 bolt for removing the capsule. The tool with a slide hammer pulled the capsule right out nice and clean. The new capsule went in clean and easy too with a 3/8" roll pin punch.

For now, the unit is shifting great. I'll have all the parts to repair the 3-4 assembly in a week or so. I'll go in and do the repair right away. It'll only take a day, since I don't need to tear the unit clear down.
 
#45 ·
Just got the Smart Tech service kit from Sonnax yesterday. Only had time for a brief visual inspection but it looks like they give you pretty much everything needed to rebuild the housing. I don't have the original apply plate out for comparison, but it definitely looks like Sonnax caught on to the lugs being too shallow. It appears that the lugs on the new plate are much deeper. They measure .167 with the dial caliper. I'll compare with the original when I have it out but there seems to be a difference. The new lugs are deep enough that the shiny tips of the apply ring legs probably won't even matter since the lugs go well past the damaged area. But, the apply rings getting swapped anyway. I'll keep the old one for a spare.

I already got the new 3-4 stack up from Dana at Pro Built. He's such a great guy, quick service. The new apply ring came from Perfection Plus just two days after I called them. $5 and they also threw in a late style 3-4 spring pack. The new springs look better than what I have so I'll probably use them as well.

I'm ready now anytime to go back into the unit to fix the apply plate and ring and replace the 3-4 clutch again. Right now it's looking like next weekend will be the time for that. I'll update once I have it done. I'll get photos during if I can but no promises. I've spent over $1500 on hotrod parts in the past three months and still no phone. Looks like I have my priorities straight after all.
 
#46 ·
Just a quick update. I went back into the unit this past weekend. Everything looked great. I installed the new 3-4 apply ring with the apply plate and backing plate from Sonnax, along with new BW high energy frictions and steels. The trans shifts beautifully and no leaks. Got the job done in one day and didn't even work too late.

I feel very good now that I have the trans dialed in so it should last a while with me pouring the coal to it.

We'll see how it does over the next few years.
 
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