4t80e Cadillac Transmission Problems? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 05-08-2008, 11:46 PM
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re 4t80e caddy trans problem

the 4t80e uses a band for fourth gear.problem? i say this becouse it does shift but slips. the computer your using is it from the same car as the motor ?if so when it sees a fault 4th is disabled. in the vehicle there is away to shift the trans on command with the temp controler.what do the codes you get mean? also there is a relearn function you must do for proper pcm controled shifts if the battery has been disconected you need to reset the shift learn this trans has no ajustable clearences in the clutch pack when you build them by the book.the computer makes up for any clearance problems with a shift relearn so it can see the volumes needed for each perfect shift.the solenoids also have a habit of breaking at the base were it ataches to the vb becouse of the black square top filter popping up under pressure if this is a problem there is a hold down for the filter through transtar.try fixing any engine codes before a this too. good luck

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Old 05-10-2008, 08:14 AM
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4T80E no 4th

Everything is the same except the valve body was taken apart and it worked fine prior to the shift solenoids going out. I can buy a new valve body cheap if this could be the problem. Cadillac told me they don't replace the solenoids, they replace the whole valve body because of problems putting it back together??? The get $1000, I paid $300 for the solenoid job.
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Old 05-12-2008, 08:24 PM
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no 4th gear

Did the solenoids break or did they go bad? The other thing is does the valve body and separator plate match? I just built one that had a plate from an earlier model that had blocked ports when you lined up one to the other,it also slipped in 4th but the B solenoid was broken and scorched clutches metal & friction material made some valves stick too. If you have engine codes the pcm maynot allow 4th.The 4t80e has a capability to read its own pressures through a snap-on scanner maybe able to watch what the shift is doing or even be able to sea if the pcm is telling the trans to shiftup ?who did the work&how long ago,warranty?One more thing have you tried shifting it with the computer it has an over ride in the diagnostics you can do in the car without scanner.if none of this points in the right direction you might have to pull the valve body and look for misassemled valve assemblies a washer on the wrong side of the spring will make it have no pressure on boost valve in the pump that was my lesson with my 1st 4t80e. also knicks on valves,grooves on accumulator pins&bores torn gaskets will give problems. good luck.

Last edited by will22; 05-12-2008 at 08:33 PM.
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