dennisr

I've actually had a problem I have yet to address until I get my exhaust back on but maybe someone can shed some light. I have a Bow Tie Overdrive tranny behind a 420 hp 383 in my 71 vert. The problem is that once it has shifted into overdrive, It will not downshift until I press the gas at least half way down. Meaning if I'm just driving through town slowly It stays in overdrive. Trying to feather the gas when just cruising around causes it to buck as the rpm's are too low for OD. On my 81 when i just barely touch the gas it shifts out of OD. My short term solution has been to drive in third gear in town. Which has only been twice, but I obviously need to correct it. I set up the TV system exactly as BTO suggested. I have a pressure increase as soon as the throttle is pressed. My thought was I probably need to tighten the TV cable so it reacts quicker to throttle response, but I'm concerned about causing too much pressure in the tranny. Is this possible or do I just simply need to adjust?

Thanks in advance,

Jvette73

It sounds like the tranny itself is fine. The characteristics of kickdown many times are built into the tranny. I would check with BTO to see if yours is doing what they built it to do. Also, do you have a toggle switch that will allow you to bypass the 12v to the 4th gear automatic lock up pin? I have a toggle on mine and when I cruise at lower speeds in 4th, i can flip the switch and the convertor wont lock in 4th. With the auto/4th lockup bybassed, I can cruise as low as 30mph in 4th without the bucking you describe. The only time I lock 4th is on the hwy at consistant speeds adove 50mph. So it sounds to me like, currently, your tranny is set up to automatically lock when its in 4th. The locked convertor in 4th gear at slower speeds is causing the bucking. Some say they solve this problem by simply pulling the shifter down to 3rd when thier cruise speeds are lower. The toggle switch will allow you to kill the 12v signal that goes to the convertor in 4th, allowing you to use 4th gear without the convertor locking. You could test this first by simply disconecting the wire from the side of the tranny. With the wire disconnected you can take a cruise and the convertor should stay unlocked even in 4th. If you like the results, re-connect the wire to the tranny and add a toggle to the circut to allow you full controll with the flip of a switch. I have miniature toggles that hide good under the ashtray lid. The second toggle allows me to lock up in 2nd and 3rd if I so desire. The only time I use lockup in 2nd and 3rd is for 1/4mi drag racing. With full throttle blasts, locking 2nd and 3rd nets me 2 tenths better E.T.

dennisr

Thanks, I like the idea of the toggle switch. Could this cause any overheating by allowing 4th gear to slip at all time except highway. I use a beCool rad and a tranny cooler so I would thinkit should be o.k.

Thanks again,
Dennis :cheers:

Jvette73

It is true that a locked convertor will not be creating heat from slippage and friction. Your extra cooling capacity should handle the task easy. BTO was the provider of the toggles and knew in advance how I would be using them. They didnt raise any warrantee issues with me on the subject. With two toggles though, you could even cruise in 3rd locked up if you want. I find it best just to keep the convertor unlocked completly for traffic and slow speed cruising. That way I can get into 4th at low speeds without the bucking and chugging. I use the lockup on the open road and hwy when i can cruise consistantly at higher speeds. What you probably felt on your '81 was the convertor unlocking in 4th then locking again when you release the throttle. In my opinion, in those conditions its better to over-ride the lockup. This way the convertor is not constantly seeking in and out of lockup causing additional wear on the lock up clutches. With the BTO trannys, the two toggle setup gives you full controll. Im not sure how to handle the lockup matter with respect to your '81 and its tranny.

Carl in LA

I'm learning to love my BTO 2004R right now and I can report that I do not have the bucking problem with the tranny locking in town and loping as low as 1000 rpm at 30 mph. I do have the same wish to make the kick down react a little quicker... I did not use the BTO laser cut adaptor to extend the throw on the throttle to cause more action on the TV... I believe I need to use the adaptor but I have not seen a clean way to attach the adaptor for that perfect swing (the stock Rochester M4MC clete is almost perfect for the 200 4R... only need about an additional 1/8" radius on the sweep to achieve perfect idle to WOT swing on the TV pushrod). I am planning a road trip out to BTO in Hesperia (100 miles for me) to let them show me their plans for a better adaptor arrangement.

Part of the situation is these strong engines.... you really dont want to push the accelerator too hard because you're going to be flyin' when it finally does kick down and grab! Perhaps driving in third in town is the common sense solution.

The other thing I am getting used to is the kick in the pants shift characteristic of the BTO built tranny... It shifts pretty hard and I worry about the rear end and universial joints taking that 1st to 2nd hit around town. Obviously I want it both ways... silky slippery smooth around town and then a kick in the pants with aggressive driving!

I did envision some kind of a cable and cam arrangement hooked to the cable to alter the TV relationship while driving to achieve a "sport" setting.... Kind of like the way you see things on more modern sports cars.


[Modified by Carl in LA, 12:58 PM 2/2/2002]

rhoeven

Dennis,

I installed a BTO 700R4 in my '81 as well. The tranny shifts into OD at 44mph(very light throttle) and downshifts into third again at 40 mph. The speeds of course depend on your differential ratio. I have 3.08
When I'm driving at around 50 mph in OD , it requires about 10 ~ 15% throttle to downshift back to 3rd.
Just check again that the plunger in the oil pan gets completely burried at WOT AND there is no gap at idle.
Further more, I set the TV-cable bracket at the carb in the 6 o'clock position at idle. This assures that the TV-cable pull distance vs. throttle travel distance ratio is highest. This also gives you firmer shifts (which I like :) )

Hope this helps.

Roger