73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => 73-87 Chevy & GMC Trucks => Topic started by: 76_Scottsdale on March 30, 2008, 06:31:56 pm
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After having had my 700R4 installed for a few months, something's been bothering me. With the new overdrive, my final drive RPM at say 50 miles per hour only dropped a couple hundred RPMS. If it has a .7 overdrive it should've dropped almost 700 RPMS. Now before anyone asks, yes I'm sure it is in overdrive, and yes the torque converter locks up once it shifts into 4th gear. I can feel the torque converter unlock if the brake pedal is pressed slightly, so I know the tranny is in overdrive. I'm extremely disappointed with the overdrive if this is all it has to offer. It is a brand new tranny under warranty from Bowtie Overdrives, so if something is wrong with it's covered. Does anyone have any ideas why I can barely notice an improvement in final drive rpms? If iI calculate the rpms if should be around 1470 at 50 mph in overdrive. It is actually at 2100 which is the 1:1 ratio, so obviously the tranny is not engaging in overdrive. The TV cable is adjusted correctly also.
I'm running 4.10 gear ratios and 305/70/16 tires if it interests anyone.
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Manually shift the transmission to verify each shift. If you shift from overdrive to drive does it shift into 3rd or does no shift occur?
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I can feel it shift into 3rd, but the RPMS only rise slightly, like only of the torque converter unlocking, about 200 RPMs or so. If I accelerate smoothly manually shifting into each gear, then from 3rd to 4th i feel it shift but it only drops about 200 rpms, which I believe is just the torque converter locking.
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bump
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I get about 1800
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Here is the 50 mph set. If you are getting 2100 rpms you are not seeing OD
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In fourth gear converter locked you should be around 1750 RPM's give or take a few...
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That's exactly what I'm thinking. The converter is definitely locked but I don't think I'm seeing OD. I've made contact with Bowtie and it's covered under warranty, now I think I get to take it out and put a new one in >:(
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Did they wire it up to lock the converter in drive? So if you shift in and out of overdrive there is no change? Just unplug the connector for the converter clutch so you aren't confused by it. Manually shift each gear.
Did you adjust the TV cable properly?
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The TV Cable is adjusted perfectly. I wired in the torque converter. It is wired so it automatically locks the converter in 4th gear. I'll try unplugging it so it doesn't lock and i'll see if there's any change shifting into 4th.
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just a thought, was the speedo gear matched to the gear set and tire size?
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It's a 4 wheel drive application there are no speedo gears.
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I unplugged the TCC wiring so I wouldn't feel it lock at all. It doesn't shift into a 4th gear at all, automatically or when I manually shift it into 4th from 3rd.
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You have 1-2-3 with normal shifts? Not late shifts?
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No late shifts. The TV setup feels just perfect, it shift right when it should. Just no 4th gear.
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Just to verify it's not a linkage issue, if you shift up manually one more does it go into Neutral?
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Yup. I talked to a tech at Bowtie today. He said next thing to do is drop the pan and verify that the 4th gear valve isn't stuck and make sure it is able to move back and forth. That's getting done tomorrow. If there's something wrong with the valve assembly, they'll ship me out a new valve body.
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When I put a rebuilt th350 into my truck the shift points were different at first. Example the shift points were all lower. It was like going from 308 rear end gears to 410s. Example it was shifting into 3rd gear at speeds where it should normally only be going into 2nd gear. I just drove mine and after 100 miles it fixed itself. Have no idea what was going on.
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Can anyone provide a picture showing the 4th gear valve in the vavle body so I know which one to un-stick when I pull the pan?
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what year is your trans?
(http://i6.photobucket.com/albums/y228/Sabaka454/700r4vb.gif)
(http://i6.photobucket.com/albums/y228/Sabaka454/700r4vbb.gif)
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I honestly have no idea because I bought it from Bowtie but it does have TCC lock up if that matters. So once the pan is off I should be able to get a small dental pick up in there and pull out that 3/4 shift valve right?
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anyone?
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no, you will not have the shift solenoids like pictured above. You'll need to drop the valve body. Take a pair of dykes or needle nose pliers and slide the roll pin up and you can remove the valve. Are you capable of taking apart the valve body and will this void your warranty?
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The way the guy at Bowtie explained it to me, he said I should be able get to the valve with out dropping the valvebody, so maybe I have the other kind of tranny?
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The other kind of tranny? What does he want you to do? Just try and move the valve with a pick tool? you might be able to move it a tad without dropping it.
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Yes, he wants me to move the valve a little with a pick to try and unstick it. He said once it's unstuck it should be fine, and if not then I'll drop the valve body and they'll send a new one.
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How much did you pay for this trans if you don't mind me asking?
I just can't believe they don't dyno test their transmissions.
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The tranny was $1295 bones. I believe the tranny was tested and sat on a shelf until I bought it which really erks me. The one thing I've ever bought from them acts up. Needless to say I'm not buying anything from them again.
If I get the pan off tonight Vile would you be able to explain where the 4th gear valve is at when you're looking up at the valve body?
Thanks for your help.
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Let me log into ATRA and see if I can find you a diagram
Here ya go
(http://i6.photobucket.com/albums/y228/Sabaka454/30vb010e.jpg)
(http://i6.photobucket.com/albums/y228/Sabaka454/30vb011e.jpg)
(http://i6.photobucket.com/albums/y228/Sabaka454/30vb012e.jpg)
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thanks i'll check back in a few i'm gonna go drop the pan.
Thanks Vile
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Man your diagrams are da BOMB VIle - IMPRESIVE!! ;) ;D
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Well I pulled the valve body last night. I completley removed the 3/4 shift valve and visually inspected it to make sure it moved freely and it did. I re-installed the valve body and the tranny still has no 3/4 shift. The tech at Bowtie suggested checking the gasket in the 4th gear servo, as this is the only other thing that he thinks could cause no 3/4 shift apart from a bad valve body. I'm going to check the servo tomorrow. Could this possibly be the problem?
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anyone have any thoughts?
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Hi, I do not want to interrupt your progress on your issue but I have been watching this thread carefully. I have a 75 and have been contemplating the same. After this is resolved, would you mind giving your thoughts on issues that you ran across in your installation. I do have a 203 and not the 205. I guess I should buy a transmission somewhere else that where you bought yours as it sounds like you seem to have to be doing way too much to fix this. I understand if it works it is better than pulling it back out but they should give you something for your time, AT LEAST!
Good Luck!
Steve.
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Well I pulled the valve body last night. I completley removed the 3/4 shift valve and visually inspected it to make sure it moved freely and it did. I re-installed the valve body and the tranny still has no 3/4 shift. The tech at Bowtie suggested checking the gasket in the 4th gear servo, as this is the only other thing that he thinks could cause no 3/4 shift apart from a bad valve body. I'm going to check the servo tomorrow. Could this possibly be the problem?
If it were me, I would nicely insist on a new valve body. Seems to me they are grabbing at straws as to why it is not working the way it should. I guess that is why I like manual transmissions, I can work on every aspect of them by myself. Good luck on the outcome, I hope they make it worth your while.
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No 3-4 Shift:
Governor weights binding.
Governor valve stuck
Governor drive gear retaining pin missing or loose.
Governor drive gear damaged.
Governor support pin in case too long or short
Oil pump assembly faces not flat
Pump cover retainer and ball assembly omitted or damaged.
Accumulator valve, throttle valve, T.V. limit valve, 3-2 control valve, 1-2 shift valve train or 2-3 shift valve train stuck.
Manual valve link bent or damaged.
Valve body assembly spacer plates or gaskets incorrect, damaged or incorrectly installed.
Incorrect 2-4 servo assembly band apply pin.
Missing or damaged 2-4 servo seals.
Porosity in 2-4 servo pistons, cover and case.
Damaged 2-4 servo piston seal grooves.
Plugged or missing orifice cup plug in 2-4 servo assembly.
Third accumulator retainer and ball assembly leaking.
Porosity in 3-4 accumulator piston or bore.
3-4 accumulator piston seal or seal grooves damaged.
Plugged or missing orifice cup plug.
Restricted case oil passage.
Faulty input housing assembly.
2-4 band assembly worn or incorrectly installed.
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:o Man, no wonder people are afraid of auto trannies! On the flip side, quite the feat of engineering that all those things can work in harmony.
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yes, auto trannies can be mighty overwhelming but i plan on diving into mine here really soon...i'm scared as heck that i'm gonna mess it up but excited to learn something new...