4l80e slips when cold

[Kevinshelton19]

4l80e in my 96 silverado sat for around 2 yrs until i just put a crate engine from jegs in. now when i first start the truck cold the trans seems to slip a bit in forward and reverse until the truck gets up to temp, it also made a bit of a whining sound at one point when i started moving forward. when i first checked fluid after i got the truck going it said fluid level was good while hot, now with about 30-40 miles on it, its down to the cold mark when hot ( will add some fluid if i dont end up changing) fluid is reddish brown and probably has 10k miles on it at most. any idea's what im up against here? sure hope i dont need a new transmission after just putting in an engine. maybe new torque converter? oh btw as far as i know trans is original to the truck which has 148k on it

 

[CRF450R]

4l80e in my 96 silverado sat for around 2 yrs until i just put a crate engine from jegs in. now when i first start the truck cold the trans seems to slip a bit in forward and reverse until the truck gets up to temp, it also made a bit of a whining sound at one point when i started moving forward. when i first checked fluid after i got the truck going it said fluid level was good while hot, now with about 30-40 miles on it, its down to the cold mark when hot ( will add some fluid if i dont end up changing) fluid is reddish brown and probably has 10k miles on it at most. any idea's what im up against here? sure hope i dont need a new transmission after just putting in an engine. maybe new torque converter? oh btw as far as i know trans is original to the truck which has 148k on it

Almost sounds like you need new clutch packs. Iv used transmissions that have sat for a long they seem to act weird for first few miles then get back to normal then I do a full fluid change and filter change. You can buy deluxe 4l60e transmission rebuild kits for about $200.

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[BIG_KID]

If the clutch packs were worn wouldn't it slip all the time.