LiftedVictory

iTrader: (1)

I picked up a transmission at my local junk yard out of an 02 Z28, it had been rebuilt last year and the engine oil pan had a dent from the inside out, I'm assuming it threw a rod. So I spent the next couple of weeks swapping it into my 02 TA. Got everything all buttoned up last night and when I fired it back up, the transmission will only engage in R, 2 and 1. No power to the wheels in D or 3. Fluid looked good from it, I did change fluid and filter. Level is good, right where it needs to be. Car was still up in the air and tires were free spinning in R, 2 and 1, no movement in 3 or D. Everyone else says 3/4 clutch pack is burned up, but how can they tell, it won't even go into 1st from the D or 3 position which tells me that it could be electronic. Any suggestion from the automatic gurus?
Thanks in advance.

6t7gto

iTrader: (1)

I found this...
http://www.silveradosierra.com/trans...rs-t21799.html

bbond105

I will have to check the manual to 100% sure but I think the forward sprag is broken. In 2 and 1 gear position the overrun clutches are applied and take over for the forward sprag and that is why only those two forward gears work.

libertyforall1776

iTrader: (2)

Pretty similar to the problem mine had, see the last page of my post here for what was wrong:

https://ls1tech.com/forums/showthread.php?t=1735865

FirstYrLS1Z

iTrader: (4)

If you can start out in 1st and then manually shift thru the gears AND ATTAIN 3rd and 4th manually,it's forward sprag. I drove for 2-3 years under that condition until the trans was pulled and replaced.

mrvedit

This is exactly right. If it still does not engage 3rd gear after manually shifting from [D2] to [D3] then the 3/4 clutch is smoked.
In either case the trans will need to be rebuilt.

LiftedVictory

iTrader: (1)

Just an update, I got it on the ground and drove it around, and manually shifted through the gears, and it took a while and made some bad noises going into second, but it seems to be working fine now from all positions. Must of had a stuck valve or something. Just needed to have some torque applied. But as soon as I pulled back in the driveway, there seems to be a crack in the radiator side tank, so fix one problem and another one appears. Hopefully I have a new one in stock at the store and it won't cost me an arm and a leg.

LiftedVictory

iTrader: (1)

Another update. So while in the D position, if I give it anything over 1/4 throttle, during the 1-2 shift, it makes a loud pop sound and neutrals out. Then if I down shift and it picks back up in 2 and then shift to 3 and back to D, it shifts fine again. Any hard parts that might be the issue, like an accumulator or a spring somewhere? Something that can be addressed with a pan drop?

LiftedVictory

iTrader: (1)

I'm starting to think forward sprag.

mrvedit

Exactly what I was thinking.
There have been several threads where the forward sprag was intermittent - it would hold for a while and then spin free.

You might try your 1/4 throttle 1-2 shift with the shifter in [D2]. In this position the overrun clutches are applied and share the load with the forward sprag. Note that the forward clutches (just two of them) are not strong enough to hold WOT, but they should hold 1/4 throttle.

FirstYrLS1Z

iTrader: (4)

My sprag blew at the strip during the 1st to 2nd shift. Drove it for 3 years by manually shifting,even did an ocassional WOT and a trip from Cleveland Ohio to Florida. Knowing that the trans was gonna be replaced,I picked up a used tranny in Indiana and another in Cincinnati,so I had 2 to swap in. Eventually 4th gear went(a loud bang) and tranny was replaced 2 days later. I HAD to do a quick swap as I was running 4.56 gears at the time and without the overdrive ratio of 4th,rpm was too high for general use. The one from Indiana is functioning fine so I still have another sitting in the garage to swap in if necessary. The 2 I picked up were complete with bellhousing and tailshaft. The OEM tranny was scrapped after I removed its' bellhousing and tailshaft housing. It's easier/quicker/more cost effective to just replace the tranny than having downtime while the tranny's being rebuilt.