Hi all,

Firstly I want to thank you all for indirectly helping with my build over the last 7 years! I have an 86 firebird trans am 305 tpi based in the UK that I have fitted a v1 vortech supercharger to and modified pretty much everything with the help of this great forum and website.

However I have a problem with my gearbox! I have finished the build and have been carrying out test runs ect and have been struggling to get my gears. Before the build I had 1-4 no problems. But now think I only have 1-3 or maybe even 1-2! I can reach speeds of around 80-85 mph at 5000rpm but have no up change into 4th and the rest of the gear changes are very speradic. The gearbox will only change at max rpm and only if I let of the throttle and then re apply it. Part throttle will also down shift very early.

I have tried to adjust the TV cable as suggested in various places on this website and also on external sources. I have attempted the wide open throttle method and then adjusting one click at a time to no avail. This does change the shift position slightly but still at very high rpm and only once the throttle is released.

I have also removed the governor and checked over that for damaged weights or springs and for cleanliness and seemed ok. I have replaced the fluid as well but not the filter.

The only thing not stock on the transmission is the mega shifter I have fitted, I have adjusted this over and over again in all gears and the pin fits perfectly. But could the wiring be the cause of the problem? I didn't use a relay as I was told that just the back up switch and neutral start wires needed to be used for this. There are 2 wire left over from the original shifter and not connected which are orange and black If my memory serves me right.

The other issue I have noticed is the TCC lock up wires were not connected correctly as the previous owner replaced the brake switch with a cheap single supply unit that does not turn the lock up off when the brake pedal is applied and has been left with a constant 12v supply Could this have caused damage to the gearbox or the lock up converter and be the root of my problem?

Sorry for such a long post but I am just not competent enough to resolve this final niggling issue in my own and your time and patients, as my auto gearbox knowledge is limited, would be greatly appreciated

Thanks in advance

Jamie

 

If you didnt get the trans rebuilt/beefed up prior to the SC install, its safe to say you killed it. It didnt take long for my turbo v6 to kill the stock 700.

Time for a rebuild to handle the SC, go bigger than you think you need. Don't waste your time with a stock rebuild; it wont survive.

Its dying and probably on its last leg, sounds like you fried the 3-4 clutch pack.

 

Thank you for your reply! I had a feeling it could be the 3/4 clutch but as there are other issues like the shift point timing and wiring possibilities I wanted to check before doing a very expensive rebuild. Was hoping to try get trough this summer with a stock gearbox and use next winter to build a monster gearbox but might have to be done early by the sounds of it

As I said my knowledge of gearboxes especially autos is very limited! What sort of upgrades would be needed to handle 400/500hp on a 700r4? And could a gearbox novice with a decent knowledge of mechanics do this or is it a specialist kind of process?

Jamie

 

Well the 700r4 rebuild is not for the faint of heart. I am attempting to rebuild mine here in a few weeks, though I have already taken it apart and done a few things. Even then its something new for me, and I have still ordered the proper manuals and still am researching on rebuilds.

I like to think of myself as very mechanically inclined, having done an ecm swap and a turbo install with no prior experience of either. I am an electronics engineer and have been working with cars since age 7; 23 years doing that now. But with that experience I was comfortable doing what I did and was successful at it.

All that aside, the best advice I can offer you is to keep researching and watching rebuild videos specifically for the 700r4, then make your decision based on your comfort level after doing your research.

At the least I would be looking to build it for 150hp over your expected power goal. Or even higher for that matter depending on your funds.

 

Ok so I have done a pressure test on my 700r4 transmission today and am below the minimum pressures stated below

Range Minimum Maximum
Park 90-110 190-230
Reverse 95-120 200-300
Neutral 90-110 190-230
Overdrive 90-110 190-230
Drive 90-110 190-230
Second 185-230 185-230
Low 185-230 185-230

I get 65 psi in P,N,OD, D and 2nd and 100psi in 1st and R when TV cable is at idle. I get around 170psi at WOT in all gears

Does anyone have any ideas what could cause low transmission pressure like this?
I know the transmission will need rebuild but want to make sure other issues are sorted as well

Thanks in advance

Jamie