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90 Reatta Transmission Overdrive


Guest RT Rothwell

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Guest RT Rothwell

Just purchased a 90 Reatta four months ago everything works fine until now. The coupe has about 89K miles and now will not shift into overdrive. It is curious though, it seems to act up when it is cold (below 50 degrees). If I drive it on the side streets for a while it will sometimes shift into OD at 50 but if I get right on the freeway soon after starting from home it will not shift. Getting terrible mileage. Does anyone have suggestions or does this mean a trans overhaul? Are there other controls besides the transmission itself?

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Guest Bobby Valines

I don't know that much about trans, the first thing I would do. Check trans fluid level, look at the fluid for small black particles in it, smell it for a burnt smell. If you do have to take it in Make sure the trans shop has a good reputation. My 89 has 140,000 mi and doesn't miss a lick,it was driven by a 65 yo lady. When i was a kid we would have to change the clutch in my friends 65 GTO every 2,000 mi. I think it matters how it was driven more then mi.

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Guest DAVESWF

There is also a switch on the brake pedal (turns it off when you hit the brakes), and I have had that go out-of-adjustment and cause the cruise to work irratically. As a check for this, if you are in a 'no traffic' area, you can put your left foot under the brake pedal and pull up on the pedal, and see if that makes any difference.

However, sounds like your problem is more likely related to engine temperature.

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Guest crazytrain2

Assuming your tranny is a 440-T4 it is somewhat unique in that it has two factors which control "shift"

The shift timing is controlled by a throttle pressure cable that connects from the transmission to the throttle body. Check this cable first. Make sure the cable is not out of adjustment.

It also has a modulator that controls shift firmness. If this modulator goes bad it can shorten the life to your transmission. Pull the vacuum line off at the transmission, if there is fluid in the line, the modulator is no good.

Your engine temp may be effecting the transmission fluid cooler (these coolers tend to be borderline undersize).

Check the fluid for color and smell (per above) you might consider adding some lube guard to fluid as well.

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Guest F14CRAZY

Is your engine temp gauge getting up to normal (roughly the middle)? I forgot the exact temp, 138f or so, that the engine needs to be at for OD to be available.

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146F is correct and the 50mph makes me think you are talking about the TCC (lockup), the shift into top gear takes place at 42-44 mph.

Had a 90 Bonnie with a stuck open thermostat, ran fine in Florida but toward nightfal on a witery trip to Indiana we'd get about 5 miles down the Interstate and it would drop out of lockup. Stop, check, and everything was fine for another five miles then would do it again.

Turned out the "hot soak" when I would stop was enough to get over 146F but a few miles at 38F and the coolant temp would drop below 146F and it would drop out of lockup.

Now I always use 180F Stant "Superstats". (plug)

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Guest steakneggs

Lockup is not the same as OD. It goes into lockup at some low speed (25?) or so but won't go into OD until 50 or so. I would do a fluid change or flush and look for debris. Steak

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Guest RT Rothwell

Thanks guys for the pointers. I think you are correct in the shift. It shifts into third at about 40-43 and into OD at 50. Most times lately it seems it will not shift at that 40-43 mark and does not drop in RPM until the 50 mph and no OD. The temp gauge runs in the straight up mark sounds like the higher degree thermostat is an option. I will change the fluid and filter even though the fluid is clear and does not smell burnt.

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Guest Bobby Valines

Most trans shops give free estimates if its just the modulator or something fairly easy for them, might not cost much. Just make sure it a honest shop. Did you try taking off the vacuum line and check for trans fluid, like crazytrain suggested. Maybe try taking off the vacuum line to the modulator, and go for a drive and see if it makes a difference.

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  • 6 months later...
Guest wally888

Wondering the outcome of this?

My 90, when bought in 2004, would not go into O D until I replaced the switch (3 circuit, CC, Brake lights and O D disengage).

Now having same problem. I removed the sound cover and re-inserted the switch. Now works sometimes.

Is there a simple way to test switch?

I know tapping brake pedal at about 60 mph on level ground should show an RPM drop as O D is disengaged.

The switch exhibits little resistance when inserting-do the retainer threads wear?

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Guest wally888

I think the switch has failed or not settleing in the right place?

I adjusted switch per FSM but still no O.D. at 50-55 mph and no RPM drop when brake pad is tapped.

As I remember RPM w/ O D engaged at 50/51 mph (90 model) was/is about 1500 RPM? Mine about 1800!

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wally,

I believe you are confusing OD with lockup torque converter operation. When you tap the brake over 50 mph, and you are maintaining a constant speed, the torque unlocks and causes an RPM increase. Not a RPM drop. The switch on the brake causes the torque converter to unlock. I agree that something may be wrong with the switch. However, if your car is running too cold (less than about 140 degrees) the torque converter will never lock.

If the transmission is not actually going into OD (4th gear) the problem is not with the switch. It would be caused by shifter or kick down linkage not being adjusted properly or an internal problem.

You can go into the diagnostics screen while driving and it will show you when the torque converter is locked and what gears are engaged. That will help isolate the problem.

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Guest wally888

I meant increase in RPM.

This car had the same problem when purchased in 04, I replaced switch.

We'un call the top gear, where RPM is at it's least, overdrive. I understand!

Guess I'll re-adjust switch, see if it corrects problem, if not, replace. At age 78 I hate standing on my head in the floor of a car! Probably would'nt like it even if I was looking up___________ (you fill the blank) dress.

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Look carefully at the diagnostics in Reatta.net. 90 is not as easy to read as 88-89 but is there.

Once you go into diagnostics mode, the HVAC graphics tell you what gear you are in and whether the TCC is locked. Is something about whether MED is lit or not or what air mode is shown but do not remember exactly.

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Guest wally888

Gitten old is a [censored]!

I now remember the last time, when I replaced the switch, it, at first did not work...however did work when I pulled up on the brake pedal.

Does same now! Do I have the switch mis-installed? I shoved it down til it seemed to bottom.

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