I have an 86 Iroc 5.0 tpi w/700R4 trans. My transmission will hit all four gears, but it will not go into overdrive. I have installed a new 700R4, but I am having the same issue. My engine revs at 3000 rpm at 70 mph. Please help

 

I'm a bit confused by what you mean when you say it will "hit all 4 gears" but "won't go into overdrive".

Are you sure it's not going into OD? There's a thing called a TCC (torque convertor clutch). It puts the torque convertor into lockup. If the TCC does not engage, it can seem as if there's no overdrive.

Have you done this: Next time you're doing 70 and the stick's in OD, move it to "D". Do the RPM's change?


------------------
-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

I'm not so sure you want to try downshifting to 3rd at 70 even if it IS in 3rd... maybe a lower speed like 55 (it should be locked up by that time)

------------------
'91 Firebird
305/TBI/700R4/T-tops
Mods: Catco high flow cat - B&M Shift kit - Taylor 8mm Spiro-Pro's - ACDelco Rapidfire Plugs - K&N Air Filter - Trans Am tail light conversion
Stereo: Pioneer DEH-P8200R - Pioneer 6x9's - Kenwood 8" Tube
'91 Pics

'87 Firebird
2.8L/MPFI/700R4/220K Miles on its original, never been rebuilt engine!
Car being parted and sold, just ask what I have.
'87 Pics

 

try bypassing the TCC,short the pins in your ALDL connector(top left & top right) together with a coule pieces of wire and a switch,engage the switch after 1st gear the TCC should grab tight. this will also eliminate the "syncromesh" that takes place from D-OD.

 

"Synchromesh" is in manual transmissions. I have been around 4L60's for a good while, and the only thing that even comes close is a "synchronized shift" wich occurs at the 2-3 shift, when the band releases and the 3-4 clutches applies simultaniously.

------------------
If you live in Southeastern US, check us out!
South East Thirdgen


ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
Ported Plenum,
TB Coolant Bypass,
SSM SFC,
Boxed LCAs,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims.

'97 Bonneville SSE

 

Junkyard, you were right. Your suggestion worked. The ECM gave me a code for the VSS and I read that that directly effects the TCC as you mentioned. I will replace it and hopefully that will solve my O/D problems....Thanks.

 

yeahhhhhhhhh! I love fixing things! I learned that from one of Ed Mahers posts a year ago, he claims it gets him another .2 on the 1/4 mi,even though its not the best thing for the transmission. I still have the switch under my dash, Its kind of fun to turn it on once and a while.
thank you GMtech,learn somthin new every day,but I swear it says "synchromesh" OD gear in one of my tech manuals.

 

I just used that lockup switch at the track. It dropped 0.18 off my time, and gave me an extra 1.7 MPH in the 1/4!

[edit] That was with a lower-than-usual launch speed too; I only went to 1800 rpm, instead of my usual 2000-up. It started raining before I could try a higher launch.


------------------
-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

[This message has been edited by TomP (edited November 15, 2000).]