Overdrive gone (thinking about swapping to 3t40) - Transmission Forum

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Overdrive gone (thinking about swapping to 3t40)
Monday, April 11, 2005 1:20 PM
I was driving to school this morning and for some reason the car refused to shift into overdrive. It shifts fine between 1,2,3 and R but only goes into OD when I left off the gas. As soon as I get back on the gas it downshifts back to 3rd. Any ideas? I haven't had a chance to check the fluid, but I'm thinking it may be a solenoid. One shop said I should just replace the transmission.

I have a spare 3t40 (I currently have the 4t40e) available. It only needs a fluid and filter change. Will the pcm handle the 3t40 without a reflash? Are all the wires and sensors the same?




Re: Overdrive gone (thinking about swapping to 3t40)
Monday, April 11, 2005 3:25 PM
The PCM won't like it, it will be trying to communicate with the TCM and it won't be there, so it'll go into limp mode.





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Re: Overdrive gone (thinking about swapping to 3t4
Monday, April 11, 2005 3:42 PM
Reflash the pcm with a VIN from a 3 speed then?



Re: Overdrive gone (thinking about swapping to 3t4
Tuesday, April 12, 2005 8:35 PM
Zach, I'll give you my VIN considering it does me no good... Let me know.

A



Josh
SLK 32



Re: Overdrive gone (thinking about swapping to 3t4
Thursday, April 14, 2005 10:57 AM
Zach, if you want to keep your times in the SOLO2 you'll want to get the gearing right. If that 3sp is from a 3rd gen, it's going to have a 2.84 final drive with the 33/37 chain drive, for an overall ratio of 3.18. You'll want at least a 3.33overall(3.33 f/d & 35/35 chain), though this might be a little slower. I would recomend some thing more like a 3.43(3.06 f/d & 33/37 chain). you could go as far as 3.73(3.33 f/d & 33/37 chain), but I dont think you'ld want to cruse at 60mph turning 3008rpm!
BTW here's your 60 mph cruse rpms for each gear( assuming you're using stock 25" dia tires):
3.18----2564rpm
3.33----2685rpm
3.43----2765rpm
3.73----3008rpm
These would be at TC lock-up, allow for more rpm when the TC isn't in lock-up.

Whith your engine mods I'd stay with the stock TC(2375 rpm stall), or you could go with a 2560 stall for a little more torque response. Let me know if you want to change the TC, I'll look-up the ID code for the one you'ld want to use.

BTW, mine's in the shop now getting repaired and the f/d changed to the 3.06 and a factory replacement TC with a stall of 2760rpm.





Re: Overdrive gone (thinking about swapping to 3t4
Thursday, April 14, 2005 1:33 PM
Well, Josh's old transmission(3t40) has 170k on it. I think I'll stay away from it.

Its looking like I'll end up replacing mine with a rebuilt 4t40e for like 1500(I only paid 3500 for the car 3 years ago...). This sucks. I could do an eco-5sp swap for that kind of money, I just don't have the time.

Whats the final drive on the 4t40e jack? Do you know of a way to keep the transmission from downshifting on me when I put it in 2?



Re: Overdrive gone (thinking about swapping to 3t4
Thursday, April 14, 2005 1:33 PM
Also thinking about installing a transmission cooler. Only got to make the car last two more years and then I swear I'm going to blow it up (no, really I am...)



Re: Overdrive gone (thinking about swapping to 3t4
Thursday, April 14, 2005 8:20 PM
I guess from inexperience with this trans would be the speed sensor.
The comp is confused whether to go into o/d or direct drive. The speed sensor would input to the comp. It wouldn't hurt to check out the speed sensor/ ring



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Re: Overdrive gone (thinking about swapping to 3t4
Thursday, April 14, 2005 8:56 PM
I currently only have one catalog with the 4T40E listed. It shows two different chain drives and three final drives. The chain dives are 35Tooth/35T(1 to 1) or 32T/38T(overdriven 18.75. They dont list the gear ratios for the f/d's, only the sungear tooth count which is 34T, 38T and 42T counts. When I get some more time I'll check some other possible sources for the gear ratio's.





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