Thread: Td6 5L40E Options

I have been talking to Gav (bacicat2000) about gearboxes after his and many others troubles. I have spent many hours researching options and at this stage I could really only offer the 2 following ones.

1.
Convert 5L40E to 5L50E specs;
• Late model R/R boxes haD larger 2nd clutch & 2nd coast clutch plates that were the same as in 5L50E.
• Weld drive shells where shaft attaches ( common practice)
• Late model R/R boxes planetary gears are the same as 5L50E.
• Use copper planetary thrust washers instead of the plastic variety.
• Jpat H/D output shaft http://www.jpat.co.uk/5L40E%20Shafts.pdf
• Sonnax kit for main pump on bellhousing; Sonnix believe this pump ahead of the valve body is the start of pressure problems with this box.
• http://www.sonnax.com/system/pdfs/14...-TIP-02-09.pdf
• Reconditioned Sonnax valve body
• New pressure regulator solenoid 5L40E Thrust Washers - Autolink Automatics
http://docs.google.com/viewer?a=v&q=...QcDLvo3cC7rw1A


• Import H/D diesel Torque Converter; the standard one is crap and I haven’t seen any local H/D versions. If you have seen this article then you would already know

GM 5L40-E transmission teardown


This would give a reliable and improved box, but I think the cost would be prohibitive and of course there are remove and replace charges, bearing replacements etc when the box is dismantled and inspected to add to these costs. The link below is for a firm in Germany that do the GM Factory rebuilds !

Fahrzeugtechnik Hetzel: Automatic transmissions - repair reconditioning



2.
GM 6L80E replacement.

• Common and cheap gearbox to buy and repair, upgrades to handle 1200 RWHP and is standard fitment for Commodores and Statesmans locally.

6L80E Performance Transmissions Torque Converters Tuning and Parts 6L90E

Circle D 6L80E Transmission Upgrades - GM High-Tech Performance Magazine



• Been quoted $350 for non-goer, $800+ for a goer and $1400 exchange for a stock rebuilt box using original T/C.
• Electronics are built in the case and programmable locally.
• The 6L80E - gear ratios: (1st 4.03:1), (2nd 2.36:1), (3rd 1.53:1), (4th 1.15:1), (5th .85:1), (6th .67:1), (Reverse 3.06:1)
• Marks 4WD Adaptors are already doing Nissan Conversions, I have contacted them, but still awaiting a reply.

Auto Trans Adaptors

• Local rebuilders are doing mods and upgrades.


[ame=http://www.youtube.com/watch?v=RShHyjloHQ0]6L80E Transmission Rebuild - YouTube[/ame]

• What we need to find out is can we use the original bell-housing and if not if the 6L80E pump can be fitted to it.
• Bell-housing adaptor ?
• Extension will original fit or will we need a custom one ?
• The 6L80E is shorter than the 6L90E so we have some variables for fitting


1) The biggest concern is that this box has 32 spline output shaft against the 27 spline on the 5L40E.
The 6L90E uses a larger output shaft that's 1.5'' 36 spline for 2wd applications and the 4x4 unit uses a 29 spline output. The 6L80E uses the standard 32 spline output like the 4l80.
2) Then it’s fitting the/an extension housing to the NV225 transfer case, I think this might be the hardest to solve cheaply.
3) If we could just plate the front of the transfer case and run the normal extension housing on the auto and using an output shaft adaptor like below to the T/C.
Circle D 6L80e Transmission

Upgrades Tailshaft Housing Photo 24



Below are comments from Gav (bacicat2000)

How is the TC supported? Just wondering if it is relying on the trannie to hold it, or if it has its own mounts? If it has its own mounting, then what you suggest may work - I see no reason why you couldn't make a plate to go on the TC as long as both the trannie and TC are supported, they wouldn't need to be physically bolted together.

Do you know how much shorter the 6L80E is compared to the 5L40E? You would need a bit of room to allow for an adaptor plate on the engine, and any mucking around with the TC. If the TC is mounted further back, the new drive shafts would need to be made - no biggy, but the price starts to go up a lot.



If you have any ideas or suggestions please post them on the forum.

Regards
Laurie

Originally Posted by harlie

Correct me If I'm wrong - The engine and Trans communicate for every gear change. The Trans 'requests' the engine to do certain things - How is this going to work? (I'm more electronics based than mechanical)

Having an extra ratio will be a huge improvement for the small engine but the top gear might be a bit tall - would be interesting to see, might just be happy to kick down earlier especially since 5th is not far below.

I'm just thinking out loud, this looks like a banger project and given my L322 doesn't see much use sometimes (ATM - its not moved in 5 weeks), if (or when) the GM trans craps out, I'm all up for something like this...

You have asked the million dollar question that I have yet to get a firm answer on. My testing has got as far as unplugging the trannie and seeing what happens. When you do this, the car thinks the trannie is in Sports mode - 2nd gear, so it won't start. Now, if you start the car first, then disconnect the trannie, the engine still runs fine, and revs no dramas, so I'm not sure what info they are swapping, but they are connected on the main CAN bus, so info is changing hands...

I have yet to check over the wiring ans see what can be done to fool the engine into thinking the trannie is there - just something else we need the answers to.