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If you wanna hear a guy that has built these for blown (and nitrous...and turbo) big blocks say that it's OK...then here I am letting you know it's OK
You can find a stock 4l85e and have it rebuilt at any number of reputable shops and it'll live just fine...better than the "supermatic" crate trans you buy.
If this is a budget build, then simply dual-feed the direct clutch and use a simple VB recalibration kit and you'll increase your tq capacity from that 460 or whatever number you've been quoting.
If this is something you plan on adding larger injectors, or better turbo, etc then the list of upgrades you should look into will be more than the "supermatic" anyway.
Thanks for all the details, very helpful.
It sounds like you are saying the SuperMatic was never a factory option and only a performance crate product. If so, then I can be sure my Bus has never had a performance trans installed, definitely stock 4l85E.
No plans for upgrades or tunes that exceed stock levels, at least not anytime soon (I am the sort of idiot who thinks a Drag Bus could be fun). If I ever get to that point, I will certainly build the trans.
I read the Thread that 1FastBrick posted about building a 4L80E and the discussion about the HD2 shift kit. Sounds like that kit will allow me to dual-feed as you suggest correct? I would be so happy if I could throw a shift kit at it an then tune to stock, which it sounds like I can, with the right kit. If you suggest a shift kit other than the HD2, I would love to know what it is.
There are multiple kits on the market that will dual feed the direct clutch yes.
Transgo is the most popular and typically easiest to install.
I've posted here before, as have others, a list of what steps to follow and which steps to skip on the transgo kit instructions.
The method transgo uses to dual feed isn't my favorite but it works fine for enough people.
Old thread but I have the same question, factory 2008 4L85E I have purchased is from a GMC 3500 motorhome with 6.6 L Duramax, the chassis is the same as the school bus in this thread. Attached you can see the LBZ was derated just for the van/bus fitment, but only the the van /bus/motorhome were fitted with the 4l85E, the trucks used an Allison 1000 and therefore had uprated power and torque. Also the towing and load capacity are nearly double for the trucks using the Allison.
From my research it appears the "Supermatic" is a modified 4L85E that GM performance sell separate to the factory unit, fair to say its equal or better to a stage 2 or 3 4L80E build, "supermatic" also has a modified valve body with increased fluid pressures.
Hard to identify the exact differences, but the "stock" 4L85E has the 5 gear planetary gears, 300M input shaft and heavier duty clutches. After market 4L85E modifications seem to be 34 element sprag and heavier duty roller clutch, different brand clutches and a transgo kit.
So if I do want to go beyond 460 FT LB (which is on the limit if I use a Cummins IS 4.5 L engine with stock tune) I would like to identify which upgrades are most important to lift the torque limit up to 650 FT LB like the supermatic.
My understanding is the sprag and roller clutches are the weak link in these transmissions, the Allison 1000 dont use them. So maybe upgrading just the sprag and roller clutch would be be all that is needed and a transgo kit.
Old thread but I have the same question, factory 2008 4L85E I have purchased is from a GMC 3500 motorhome with 6.6 L Duramax, the chassis is the same as the school bus in this thread. Attached you can see the LBZ was derated just for the van/bus fitment, but only the the van /bus/motorhome were fitted with the 4l85E, the trucks used an Allison 1000 and therefore had uprated power and torque. Also the towing and load capacity are nearly double for the trucks using the Allison.
From my research it appears the "Supermatic" is a modified 4L85E that GM performance sell separate to the factory unit, fair to say its equal or better to a stage 2 or 3 4L80E build, "supermatic" also has a modified valve body with increased fluid pressures.
Hard to identify the exact differences, but the "stock" 4L85E has the 5 gear planetary gears, 300M input shaft and heavier duty clutches. After market 4L85E modifications seem to be 34 element sprag and heavier duty roller clutch, different brand clutches and a transgo kit.
So if I do want to go beyond 460 FT LB (which is on the limit if I use a Cummins IS 4.5 L engine with stock tune) I would like to identify which upgrades are most important to lift the torque limit up to 650 FT LB like the supermatic.
My understanding is the sprag and roller clutches are the weak link in these transmissions, the Allison 1000 dont use them. So maybe upgrading just the sprag and roller clutch would be be all that is needed and a transgo kit.
.
I like the Sonnax Power Pack or Performace Pack better than the Transgo HD2. I cant remember the Sonnax exact name.
Also the Overrun Clutch Manifold they offer now to help take load off the Sprag.
Thanks RDF, Am not as concerned with the transmission strength as the torque converter, even thinking of A BOLT TOGETHER UNIT so I can experiment, dont have a converter shop close to me. This ATI kit might work:
Anyone ever used one of these ? Can I use the turbine. guts and stator from my old unit ?
You would be better off talking to Pete at Circle D about a converter.
Ive used triple disk Circle d converters in 4l80s and locking them up with 800ftlb TQ.
You need to have a good input shaft to be able to hold the torque locked up like that tho. And the tune needs to be perfect with pressures and apply times.
RDF1 am looking at that now, here in Australia not a lot of custom torque converter shops and the few here dont deal much with diesel engines.a CIRCLE D bolt together would be good, thinking a low stall speed like 1400 rpm
Apr 11, 2023 | 09:06 AM
