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4t65e non HD trans and L67

M

meritt

New member
As you may have seen in my earlier post the transmission has died in my son’s car. We had just recently completed a 2001 GTP L67 SC engine, PCM, and (recently GM Remanufactured) HD trans swap replacing his old 2000 GT L36 engine, PCM, and trans. We did this when the intake gasket leaked and ruined the motor at around 72k miles.

We still have the original transmission (the non HD version) that came out of his car so I am considering swapping it back into the car. I know that we will need to have the PCM tuned for this swap but what other problems would we run into? IE what should I expect regarding the different gear ratios when I pair the old GT trans with the L67 engine and Torque converter?

Also assuming the HD differential is OK in the GTP trans I think I will pull it out and drop it into the GT trans. Is this a good Idea or more work than it is worth?

If it looks ok can I use the old torque converter that came with the GTP unit or am I asking for trouble?


Here is a new update on the trans I want to put back in the car

The original GT trans was running good before we swapped it but when we dropped the pan we saw about 4 small metal shavings in the filter and two more in the bottom of the pan. They don’t look like much and when I drug a magnet through the fluid I didn’t pick up much at all other than these chips? The fluid smells good and after sitting overnight there is just a little non ferrous sludge in the bottom. Should I be worried about this or not?
trans shavings.jpg

Thanks for any help guys.
 


That is basically what the GT-GTP differential swap entails.. The cover, and end gear. The L36 and L67 flywheel patterns are different sizes. The L36 torque converter is smaller and wont bolt to the GTP flywheel.

You can use the GTP torque converter and flywheel with the GT tranny, swap over the HD cover and diff, and get the shift points fixed with a tuner.
 
If you don't want to have to go through any of the pcm tuning and you have a 3/8" and 1/4" torque wrench I'd suggest investing in 2 channel plate gaskets. If you don't take the oil pump or valve body apart these are the only 2 gaskets you'd need to swap out the 2.93 gear ratio sprockets.....also while doing this swap out to the HD diff and HD diff cover and you'll end up with the exact replacement for the trans that just went bad.....and wont have the hassle of having to make any changes in the PCM setting, torque converter, and flex plate.

With putting in a new trans I would always suggest a re-manufactured torque converter especially if the previous trans had a failure. Lots of crap can be left over in the converter and you're only contaminating the new trans by not replacing it and also flushing the trans cooler.
 
I like the idea of swapping the sprockets, especially if I really don’t have anything else that would be required to make that setup work.

What do you think about the shavings I found in the trans that I want to reinstall?

My first thought is, not a big deal probably some casting material, but then again I am paranoid now so… Trouble is I don’t have the time or cash to be excessively paranoid and just replace everything…
 
With that little, it's very possible that you can run for a while w/o issue. I doubt it's just casting. Double check the diff cover to see that the pin isn't digging into it.

Reprogramming or swapping the gears, as Greg said is pretty straight forward. I would also change the output shaft and diff. (Split the diff off the output shaft and make sure the shaft comes out the driverside of the trans), also remember the o-ring on the input shaft or you will destroy it.
 
I think this is the way I want to go so hopefully those parts are good in the HD Trans!

I also found a “GM 4T65E 4Th Clutch Hub & Shaft Updated Hardened Splines Brand New 97-On (99924)” from usa.industries on EBay for only $38.50. That seems like a pretty good deal, has anybody dealt with them before?

My concern is it doesn’t appear to be discolored from heat treating as was mentioned in a previous post. When I asked about this the gentleman said it is because it is hardened not heat treated and is better?

I see everyone is recommending Dexron VI but I have read that not all seals prior to 2006 in Allison transmissions were compatible? (I was thinking using it in my 01 GMC 8.1)
I realize these are not Allison transmissions we are dealing with here but does this concern anyone?

I also think I will drop in the ZZP shift kit since we won’t be tuning the PCM now.:)
 
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When you say ZZP shift kit, are you talking the super cheap one?

If so.. it's spacers you can pick up at a hardware store. 3 3/4" and 1 1/2" get metal, not plastic.
 
Yeah it’s only some springs and spacers, unfortunately I already ordered the Kit before reading your post.

Any thoughts about hardened versus heat treated splines on the 4[SUP]th[/SUP] gear hub?
 


well hell... you are spot on there weren't even springs in the kit just plastic spacers.... not a complete rip off at least they give you some decent instructions...
 
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