4L80E No Reverse!

[GasGuzzler]

GM Service Information actually has a "No Torque in Reverse and Third" chart and a "No Reverse" chart. Here's the latter...

No Reverse
Checks
Cause

Case (7)
The rear band anchor pin is broken or the pin is not positioned.

Center Support (640)
Leaking at the case, or the support is broken.

Center Support Seal (639)
Leaking

Center Support Bolt (25)
• The bolt is loose or broken.

• The feed hole is blocked.

Rear Band (657)
Broken, worn, or not anchored

Rear Band Apply Pin (73)
The pin is too short or the pin is binding in the case.

Piston (65)
Binding in the case

Seal (66)
Leaking, damaged, or worn

Gasket (63)
Damaged or displaced

Cover (62)
Damaged

Bolts (61)
Broken, loose, or missing

Checkball
Missing

Fluid Pressure
Too low

Direct Clutch Components

•Reaction Plates (618)
The splines are worn.

•Friction Plates (611)
The splines or the friction are worn.

•Spring Assembly (607)
Jammed

•Housing (623)
Cracked

•Piston (619)
Leaking

•Seal (620, 621, 622)
Leaking

•Ball Check
Leaking



Now for range reference.

[Kros383SS]

things you could have checked before rebuilding when losing reverse and third...

Solenoid "B" in the valve body. Stuck "off" condition. leaking seals. burned out, no voltage, no signal from PCM, loose connection.
2-3 shift valve item 312

Doesnt have any solenoid's anymore, coverted to full manual. I lost 3rd and reverse after leaving the 3-4 shift valve and spring out when I was going through the VB trying to figure out why 2nd gear would not hold above 3500 RPM.
After that I lost 3rd and reverse, so I tore it down and found the direct clutches burnt along with the Int. Band which looks like it was skipping on the drum. The 4th clutches looked ok but there was burnt spots on the steels.

I have good pressure so Im assuming I have good pressure to the Reverse circuit but the band is not engaging.
Only problem with that is I have 1st gear which also uses the rear band and low/reverse piston.
3rd gear works fine so Im also assuming the direct clutches are engaging.

Im thinking real hard on this one before I pull the trans and it could be something in the VB or the rear apply piston.

Also after the rebuild Im getting close to 300 psi when I give it gas, Its vacuum modulated now. Didnt do that before.
Park, N, D idle psi-175 quick tap on the gas gives 300psi
Reverse idle psi-150 quick tap on gas 300 psi.

I was hoping to get my hands on some fluid flow diagrams so I can see whats going on in each gear.

I have the range ref. in the ATSG book which helps me somewhat.....

[Vince_B]

You do have the manual valve in the correct postion? Seen it do some weird stuff in my days when it is not. If you have engine braking in low then the band is ok. According to the power flow for reverse to work, the OD roller, direct clutch and the low band are applied. As far as solenoids in your case it does not apply. In a regular unit even though the 1-2 shift solenoid is energized it does not need to be on in order for the trans to have reverse. With you having 3rd gear I would think that the direct clutch is ok. I have seen where if the late style OD roller cage is just a little off when assembled, it will not hold. This is the style that uses a blue and black plastic cage. If you do take this unit a part, do us a favor and carefully remove the input shaft, over run drum and OD planet assembly. Make sure that the planet locks in one direction and free wheels in the other direction. This might be where your issue is. Another thing to check is do you have the little check 3/16's ball installed for the gear command function. This is the one that is installed between the valve body and the plate supplied from transgo. I do not remember if the hd-3 kit uses this but it is definitely something to check. Best of luck with this one. Vince B

[Kros383SS]

If you have engine braking in low then the band is ok. According to the power flow for reverse to work, the OD roller, direct clutch and the low band are applied. As far as solenoids in your case it does not apply. In a regular unit even though the 1-2 shift solenoid is energized it does not need to be on in order for the trans to have reverse. With you having 3rd gear I would think that the direct clutch is ok. I have seen where if the late style OD roller cage is just a little off when assembled, it will not hold. This is the style that uses a blue and black plastic cage. If you do take this unit a part, do us a favor and carefully remove the input shaft, over run drum and OD planet assembly. Make sure that the planet locks in one direction and free wheels in the other direction. This might be where your issue is. Another thing to check is do you have the little check 3/16's ball installed for the gear command function. This is the one that is installed between the valve body and the plate supplied from transgo. I do not remember if the hd-3 kit uses this but it is definitely something to check. Best of luck with this one. Vince B

Well it does not have 3rd gear either. I hooked up the DS and you can pretty much tell there is no rpm drop from 2nd to 3rd.

I pretty much tore back into it and dropped the VB and I noticed one thing...which requires a call to Transgo.

The transgo vb gaskets have two holes that are open and the gaskets that came with the rebuild kit do not have these holes. Its page 6 step 6 on the HD-3 instructions.

U use 7 ck balls for the case just like the HD-2 instructions but u discard the checkball in the 3rd/reverse bushing in the VB

thanks for the help

[Vince_B]

These holes in question, does the separator plate have a hole in these locations? If not I would think this is not an issue. In my last post I thought you had 3rd gear. When you say you have 1st and second is this in the manual ranges? Or in D3 or OD range? I will have to take a look to see if I have a set of -3 directions and take a look tomorrow when at the shop. Vince

[Kros383SS]

These holes in question, does the separator plate have a hole in these locations? If not I would think this is not an issue. In my last post I thought you had 3rd gear. When you say you have 1st and second is this in the manual ranges? Or in D3 or OD range? I will have to take a look to see if I have a set of -3 directions and take a look tomorrow when at the shop. Vince

Yes you had to drill these two holes in the sep plate. It seemed I had 3rd gear without the DS installed...upon installation you can accuratly tell there is no rpm drop shifting into 3rd.
Only way to shift this trans is manually now.

Called transgo you have to use the supplied gaskets or make holes in the gaskets that dont have them.
I asked them what these two holes did and Larry said it completes a circuit.
No kidding....I know that. Seems it has to do something with 3rd Exhaust.

Really wish I had some fluid flow diagrams.....would make this 100 percent easier IMO.

[Vince_B]

Take a picture of the plate for me so I can try to tell you what is going on there. I'll take a look in my book for you if you do. Vince

[Ray@NP]

check the rear band apply pin might be too short or may be binding in case.

[builtyota]

Great! Thanks Richard, I'll give you a call today when I have some time , hope you do too. My email is jeffsemale@hotmail.com if ya could send that PDF to me, I would be indebted to you.

I re-read the thread and realize you were using a rebuild gasket, didn't catch that the first time, does the T-go gasket have the holes already or do you have to cut them too? I guess I'll just give you a call.


And regarding the pin, why would putting the kit into th VB cause the pin to be short now? I know some guys add 1/4" to it. Does the servo not apply as much/not travel as high in the bore now, you would think it would be the opposite! Like I said, it worked fine just before the kit, the transmission was rebuilt a few years ago by a trans. shop, (they had added the SK bypass valve kit too). I'll get my hands on a caliper and check it, maybe they already put a longer pin in during the rebuild.

I appreciate the help guys!

Jeff

[builtyota]

My reverse/low servo pin is about 4.33" long, seems it is the early 400/4l80e pin. According to this company: http://www.wittrans.com/c-713-4L80E.aspx?pagenum=48 (D34913F).

It's the shortest pin there is, they go up to 4.861" , pretty much 1/2" longer. Should I lengthen it anyways, even if it is not the root problem?


I don't want to hi-jack here, but if someone has the same problem this info will probably help them. Plus, the guys that are in this thread are hopefully subscribed to this topic already.