Transmission questions???

bricud · #1 02-03-2011, 10:19 AM

I have a 1994 SVX LSI AWD with 146K on it. I have had it since 126K and assume the trans is original.

I noticed that when the car is cold, and usually for the first 30 minutes of driving or so, the tranny doesn't seem to fully engage into 4th gear. When driving at 60 mph, the tach reads about 2300 rpm. When you give it gas, it goes up to maybe 26-2800 rpm. After a while, it seems to lock into 4th gear and is taching 2000 rpm right on. When you give it gas, the rpm doesn't jump, but remains at 2K as the engine pulls until the veicle speed increases.

I am familiar with how the car holds in third gear until it warms up, but this is after the shift from third to fourth.

Bottom line, most of my driving involves shorter runs, but at highway speeds, and when it doesn't lock into 4th, my mileage is kind of crappy (18-19mpg) with about 75% being highway miles. I am wondering if I have a tranny problem?

Also, I read somewhere someone assuming that the blue torque converter is not the factory converter?? I recently replaced the motor and have the bright blue converter. Does this tell me it has been replaced?

Thanks,

Brian

Huskymaniac · #2 02-03-2011, 11:19 AM

I am no expert but it sounds like you are describing torque converter lockup. The TC won't lock up until the ATF is warm enough. Do you have an external tranny cooler? If so, how big?

Manarius · #3 02-03-2011, 11:44 AM

The Torque Converter won't lockup until the internal ATF temp is at least 125deg F (although, I think it's actually higher).

If you're not doing long highway drives, you're going to get around 20mpg. You need to do long highway drives in order to see greatly increased mpg.

Red94Svx · #4 02-03-2011, 11:51 AM

Yea your miles per gal. Is not that bad considering the max is 25 ish i drive about 50 miles to work and the best i have ever got was 24 and this is in a fwd svx...

Huskymaniac · #5 02-03-2011, 12:07 PM

MPG will suffer in extreme cold and I assume you have extreme cold in MN. Have you switched to synthetic ATF? If not, I highly suggest it along with synthetic in the differentials. I have not yet been convinced to use synthetic in the engine, however. There are good arguments to changing the oil every 3-4k miles regardless of the type of oil. If I am going to do that, I am not spending the $$$ on synthetic. I have opted for Quaker State High Mileage oil instead as it has a good viscosity index and a good additive package for high mileage engines. It is a little more money but not nearly the bank breaker synthetic oil is. The high VI will keep your 5W30 oil from turning to molasses in the MN winters.

dcarrb · #6 02-03-2011, 01:42 PM

Quote:

Originally Posted by bricud

Bottom line, most of my driving involves shorter runs, but at highway speeds, and when it doesn't lock into 4th, my mileage is kind of crappy (18-19mpg) with about 75% being highway miles. I am wondering if I have a tranny problem?

As others have noted, the torque converter won't lock until the transmission thoroughly warms-up. Most trips, this occurs right about the time I get to where I'm going, meaning my typical commute mileage is right in line with yours at 17-19 MPG (highway mileage is high 20s). So no, you probably don't have a problem.

dcb

bricud · #7 02-03-2011, 03:04 PM

I don't have an external tranny cooler. And it does sound like, based on your response, that it is simply the needfor the tranny to fully warm up before it will lock the torque converter. I am not running synthetic ATF.

Doesn't sound like there is any way to get it to lock sooner to improve mileage??

Brian

Manarius · #8 02-03-2011, 03:17 PM

Quote:

Originally Posted by bricud

I don't have an external tranny cooler. And it does sound like, based on your response, that it is simply the needfor the tranny to fully warm up before it will lock the torque converter. I am not running synthetic ATF.

Doesn't sound like there is any way to get it to lock sooner to improve mileage??

Brian

Locking sooner isn't going to resolve your problem. Longer highway speed drives with less stops are the only thing that's going to improve your mileage.

That and maybe swapping to a 5MT so you could short shift constantly. Still wouldn't resolve your short trip problem though.

Huskymaniac · #9 02-03-2011, 07:48 PM

Quote:

Originally Posted by Manarius

Locking sooner isn't going to resolve your problem. Longer highway speed drives with less stops are the only thing that's going to improve your mileage.

That and maybe swapping to a 5MT so you could short shift constantly. Still wouldn't resolve your short trip problem though.

I was always told that a tranny is more efficient when the TC is locked.

Manarius · #10 02-03-2011, 08:37 PM

Quote:

Originally Posted by Huskymaniac

I was always told that a tranny is more efficient when the TC is locked.

Well, of course it's more efficient because it doesn't have to slip and waste that energy. However, when you're stopping and going, the TC isn't getting time to lock up or it's locked up so infrequently that the fact that it's locked barely contributes to efficiency.

Stop and go traffic and 3600lb of metal is going to kill your gas mileage. Plain and simple. Those problems are not easily remedied and doing something to lock your TC faster isn't going to fix those problems.