TC lockup ?

lee · #1 09-06-2002, 02:24 PM

Equipment:
New radiator, rebuilt tranny, 17K Hayden cooler in series (after stock).

Performance:
Tranny will not shift into 4th until some warming up, as expected.

TC will not lockup until well after engine is up to normal temp (by dash gauge). The engine is usually at temp after driving about a mile. The lockup seems to first occur about 3 or 4 miles into the drive (all this with the ambient around 75 or 80F). At what I belive is TC Lock there is no clunk or other noises. Watching the tach, the engine smoothly slides down about 250 to 300 rpm in a couple seconds duration. To minimize my influence on the process, this is on cruise control at 50mph and a flat road (hiway A1A on my way to work for those who have live/visit FLA - about as flat as they come).

Question:
So, is the longer delay in lockup what one should see or is it supposed to occur any time the fluid warm enough to allow shifts into 4th?

Beav · #2 09-06-2002, 03:49 PM

Not to say mine is operating perfectly (but I have no problems with it - yet...) but it will go into OD as soon as it reaches the correct speed in the morning. Usually within a few blocks. What is it, 50°F before its supposed to be available? You should have no problem hitting that down there.

lee · #3 09-06-2002, 04:59 PM

Not sure I understood your answer, probably because my explanation lacked some info. By the time I hit A1A (4 blocks of 20mph speed limit) the car will shift into 4th gear (overdrive) with no problem. The engine hits normal temp about a mile down the road.

My concern (maybe) is that the TC lockup won't cut in until maybe three miles down the road (in the morning, less in afternoon heat). Once it does cut in, subsequent lockup occurs easily and smoothly. Here's the routine (once it has started to work): I hit 50, put on (or resume) cruise control, take my foot off the gas, and within a few seconds at stable speed I can see lockup occur by the tach dropping a couple hundred rpm. On short stops I see no problem with lockup once at speed. This is only following a cold start. So I guess I'm asking if OD works at one temp (50F or thereabouts) and TC lockup at some higher temp.

Mostly I'm trying to make sure I understand this thing before my rebuild warranty ends.

As an aside it's never been below 50F for the last couple years, so minimum temp isn't the problem.

Beav · #4 09-06-2002, 07:27 PM

I would expect it to wait for a period of stable cruising speed before it locks up. If you were to drop out of lock up to go up...uh, over a causeway

, I would expect it to go back to lock fairly quickly.

Yeah, it never goes below 50 now that I sold my dune buggy and I don't live there anymore.

Ron Mummert · #5 09-06-2002, 08:46 PM

Uhhh... So that period of time between the shift to OD (4th) & the lockup occuring is called what? Is this the interval where if I had a tranny temp gauge it'd be up around 5000 degrees? I'm not sure I can deal with the truth on this one. Thanks Lee & Beav for raising my blood pressure.

Ron.

Earthworm · #6 09-06-2002, 09:01 PM

I've noticed that it takes up to 10 miles before TC lockup. I just received my tranny gauge and will install that monday.

I still think my TCU is not working properly though.

vkykam · #7 09-06-2002, 10:00 PM

Lee,

Not that mine would be the "perfect" example, but mine does exactly the same thing since I bought the car and had the tranny cooler installed. I didn't pay attention as to whether it did it before the cooler was installed though.

As the weather starts to cool here, I expect lock up to take longer and longer, and by the time snow flies here, it probably won't lock up for 5 or 10 miles.

My 1.3 cents.

VK

Jamsvx · #8 09-07-2002, 02:10 AM

Hi.

Since you will be putting in a tranny temp gauge, can I get your advice/comment on where to locate it and the like??

I too would like to join the SVX Tranny Temperature Increase Cardiac Arrest Club!!

In all seriousness, your thoughts on the install process would be great.

Thanks

James

immortal_suby · #9 09-07-2002, 07:37 AM

With 2 svx's and 4 trannys worth of experience I find that they all had to be warmed up to about 150 degrees to lockup the TC. In cold weather this could take several miles. With all the coolers on mine I have even had it unlock doing a steady 80mph in the northern states cold weather. If you want it to heat up faster to lockup try doing some nice easy part throttle climbs through the gears - the ones where you never tach past 3k and it shifts long and smooth - if you had a tranny temp gauge you'd scare yourself watching the temperature climb.

lee · #10 09-07-2002, 09:45 AM

Where to install a tranny temp gauge is an interesting question and I'm NOT a tranny expert. The easiest would be (in the US anyway) to buy the Perma-Cool filter/gauge combo package (about $80US). That measures the temp as the fluid leaves the tranny and should be somewhere near the top of the scale. Of course then one couldn't use the Subaru filter (and Aredubjay would disapprove

). I have heard of people tapping a hole in the tranny pan for a sensor, but that's where the fluid goes after running through the cooler(s).

I haven't given up the idea of tapping into the wires coming out of the tranny itself. The voltage/resistance values given in the manuals imply a curve that looks like a thermistor using a constant-current scheme on a 2252ohm thermistor. That would put the sensing device right on the valve body - which IMHO would be optimum.

I know that some Jeep products used a thermistor in this range for water temp, but their gauge is built into a pod with speedo, etc. There aren't any wrecking yards near me or I'd be out cruising and checking other makes/gauges - when I find the time.... I have no idea what stand-alone temp gauges (VDO, AutoMeter, etc) use for a sensor so I can't tell if a commonly available aftermarket gauge could be used with the built-in sensor. Maybe I should write to some of the companies and see if they will give up the info - another rainy day project.

Jamsvx · #11 09-07-2002, 06:14 PM

Quote:

Originally posted by lee
Where to install a tranny temp gauge is an interesting question and I'm NOT a tranny expert. The easiest would be (in the US anyway) to buy the Perma-Cool filter/gauge combo package (about $80US). That measures the temp as the fluid leaves the tranny and should be somewhere near the top of the scale. Of course then one couldn't use the Subaru filter (and Aredubjay would disapprove). I have heard of people tapping a hole in the tranny pan for a sensor, but that's where the fluid goes after running through the cooler(s).

I haven't given up the idea of tapping into the wires coming out of the tranny itself. The voltage/resistance values given in the manuals imply a curve that looks like a thermistor using a constant-current scheme on a 2252ohm thermistor. That would put the sensing device right on the valve body - which IMHO would be optimum.

I know that some Jeep products used a thermistor in this range for water temp, but their gauge is built into a pod with speedo, etc. There aren't any wrecking yards near me or I'd be out cruising and checking other makes/gauges - when I find the time.... I have no idea what stand-alone temp gauges (VDO, AutoMeter, etc) use for a sensor so I can't tell if a commonly available aftermarket gauge could be used with the built-in sensor. Maybe I should write to some of the companies and see if they will give up the info - another rainy day project.

Thanks for that. I am making inquiries on Monday as to whether Australia got that update filter kit - if not, I may need to call on some assistance from my Stateside friends

There is a fellow in one of the dealerships who is the service manager and was trained on the SVX's so hopefully he should be able to assist.

Oh....Kvox (4ws SVX) and I met up yesterday - and then bumped into another SVX so we had 3 of them going down the freeway...very nice!! Photos on the way

Jamsvx

Beav · #12 09-07-2002, 08:56 PM

I don't recall ever seeing any ground rules regarding the best location for an A/T temp sensor. I think I would use the 'weakest link in the chain' method and look for the hottest point, probably as the fluid leaves the tranny, heading for the cooler.

If you use an aftermarket trans temp gauge it should come with enough fittings to get you into trouble. Barring that, take a trip to your parts store, find a roll-around stool and park yourself on it, in front of the Weatherhead fittings cabinet. After sitting there for a while, you should be able to dream up a scheme for installing the sensor in the line. Deduct one I.Q. point from your score for every thirty second interval spent there.

svx_commuter · #13 09-08-2002, 08:33 AM

Hi lee,

I use a digital thermometer that runs on one AAA battery. It has an LCD display and I bought it from McMaster Carr for about $30 dollars. I have it attached to the outsdie of the trans fluid pipe coming out of the tranny. It is wrapped with teflon tape and some of that white foam sheet insulating/package material and then wrapped with more teflon tape and some wire ties.

It is real easy to install and the readout can sit on the dash. No need to go thru the firewall as the wire can be routed to the fender door junction and then routed inside past the door weather stripping.

I usually drive about 3 miles before getting on the highway and then at 60 mph it locks up in maybe about 4 or 5 miles with hot weather 80-90F.

Have you notcied any change in when it locks-up since it was rebuilt?

lee · #14 09-08-2002, 09:03 AM

I only had it for about a thousand miles before the rebuild, so I can't honestly say I noticed anything out of ordinary (it was my differential that died, not the tranny). While it was apart the tranny had some new components put in (clutches, solenoid pack, TC rebuild), and I'm assuming from comments in this thread that the behavior I'm seeing is OK.

As to your "external gauge"...think you could measure the resistance at a couple different temperature points across the probe wires (assuming they can be disconnected)? If the curve fits the same as the built in temp sensor you could actually use the Suby internal sensor as the input to your display.

svx_commuter · #15 09-09-2002, 05:52 AM

Hi Lee,

My thermometer is on the outlet of the tranny and that is after the TC adds heat to the fluid. The only accurate temps will be when the TC locks up, above 145F. When the TC locks up the fluid by-passes the TC so this should be close to the sump temperature where the temp sensor for the TCU is located. So I could get some readings between 145 and say 180 on the highway with TC locked up. Would that be any good?
Then I have to find the time to tap into the TCU wires but I have been wanting to do this anyway. So maybe it will get me to do it sooner