What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

Quadrasteer 8.1L Suburban tow rig

2003 Suburban 2500 Quadrasteer camper towing 8.1L 6.0L swap 4L80-E
Overview Gallery Discussion
Are you saying the oil pressure switch (red) is hard to change in an GMT800 or in a square? I know I've done it on a GMT800/5.3L, but the 8.1 intake manifold is kind of ridiculous tall. Or are you suggesting to grab a new crank position sensor (yellow) before dropping it in? I've read that suggestion - probably in @Larry 8.1 resource thread. (Not my engine pictured)

rear sensors.jpg
 
This is mine as it was getting ready to go in my Suburban back in 2015. The oil sending unit I use is a D1819A with a PT2326 pig tail. This is a single wire sending unit that only runs the gauge. If it were me, I’d put a fresh 12575172 crank sensor in it while you’re there. Spend the money for a GM sensor and not a ching chong China sensor off Amazon. This is one sensor that you don’t want to skimp on as it will be near impossible to change once the engine is in the truck.
16689082610_dc995c5c06_c.jpg
 
Yea, I'd do both too, but I think the one I did was your red circle. I did change mine out with a few different combinations of extensions, but it wasn't super easy.

Also, I think my 8.1 (3:73 gears) turns around 2200-2300 rpms around 75 mph (going from memory). Definitely over 2000 rpms. It's happy in that rpm band.
 
Looks like the earlier crank sensor was problematic and likes to get stuck in the block - 12556427, ACDelco 213-942:

12556427.jpg

It's been replaced by a better one which has only the single O-ring - 12575172, ACDelco 213-1556

2131556.jpg

What's slowing me down is all the broken exhaust manifold studs. 4 came out with a wrench, I got 4 more with the welder and there are still 4 in there that have to get drilled, one of which has an extractor broken off in it. So I'm gathering lefty drill bits and an 8mmx1.25 tap for repair. Meanwhile I've cleaned all the removable parts with needle scaler, wire wheel, etc. and been painting.

Found an eBay seller doing (10) 41-983 spark plugs for $30, then used the AC Delco $2/double platinum rebate, so set of plugs for $10 + 2 spares.

Finally found what I think is an OEM dipstick tube and ordered it (12570590), as it's been discontinued as while back and Dorman claims they don't offer one.
 
Last edited:
The good news is the double O-ring 12556427 is extinct. The part number still shows as valid most places you look but supersedes to the 12575172.

Yes, the exhaust studs are a friggen joke. I can’t understand why GM and PSI (PSI still uses those itty-bitty studs on the new 8.8Ls) but I personally feel the reason the break is due to the piss poor engine mounts on the GMT800 trucks where these engines come from (4.8 on up to 8.1s and dirtymaxs). There hasn’t been an 800 truck I’ve seen with more than 100K miles that doesn’t need engine mounts. Funny thing is you can’t really feel the broken engine mounts as easily like with older trucks however the quickest way to know if they need mounts is to look at the air induction pipe. If it laying on the fan shroud you can guarantee it needs mounts. Once the mounts cave the engine drops down around an inch then it puts the exhaust Y-pipe under stress where eventually something has to give and it is usually the right rear studs first followed by the left. I feel this is the reason why even after 10 years my K10 hasn’t broken exhaust studs yet even with some pretty serious frame twisting on trails.

Also, there are a few different dipstick tubes for 8.1s but if I recall the actual stick was the same for all the tubes except G-van. The most common tube is the 12570590 that you mentioned and the dipstick I used in mine is a 12575123. I don’t have the later tube number though…..dunno why I didn’t add it to my spreadsheet back then. There are several hits on eBay for the stick and tube….probably were you got yours.
 
Larry said:
The good news is the double O-ring 12556427 is extinct. The part number still shows as valid most places you look but supersedes to the 12575172.

Yes, the exhaust studs are a friggen joke. I can’t understand why GM and PSI (PSI still uses those itty-bitty studs on the new 8.8Ls) but I personally feel the reason the break is due to the piss poor engine mounts on the GMT800 trucks where these engines come from (4.8 on up to 8.1s and dirtymaxs). There hasn’t been an 800 truck I’ve seen with more than 100K miles that doesn’t need engine mounts. Funny thing is you can’t really feel the broken engine mounts as easily like with older trucks however the quickest way to know if they need mounts is to look at the air induction pipe. If it laying on the fan shroud you can guarantee it needs mounts. Once the mounts cave the engine drops down around an inch then it puts the exhaust Y-pipe under stress where eventually something has to give and it is usually the right rear studs first followed by the left. I feel this is the reason why even after 10 years my K10 hasn’t broken exhaust studs yet even with some pretty serious frame twisting on trails.

Also, there are a few different dipstick tubes for 8.1s but if I recall the actual stick was the same for all the tubes except G-van. The most common tube is the 12570590 that you mentioned and the dipstick I used in mine is a 12575123. I don’t have the later tube number though…..dunno why I didn’t add it to my spreadsheet back then. There are several hits on eBay for the stick and tube….probably were you got yours.
Click to expand...

congrats on the March calendar pic!
 
The new dipstick tube mounts to a hole in the head and eliminates the bracket that used to go there and hold the temp sensor connector. The old one mounted to one of the exhaust studs. The dipstick stick-out measures 1/8" longer, but it's hard to be exact when the old one is broken. We'll call it close enough.

20200310_152504.jpg

The CPS was the older style. I didn't realize the connector rotated 90 degrees, but it should be even better, if anything.

20200310_155923.jpg
 
OK, a bit of progress. DS head is clear. Still 3 broken in PS.

20200310_174642.jpg

Yeah, the 6.0 that's already installed and running well has been looking pretty attractive.

I might order one of these universal drill guide things and start going at it. I should get some prices from machine shops and consider pulling at least the one head.

https://www.amazon.com/gp/product/B01A8Q3BCE/ref=ox_sc_act_title_2?smid=A42WAWTAXK2UG&psc=1

I'm wondering if the key is to drill into the head a bit to eliminate the outermost section of threads where the rust has fused things together. That's basically what I did on the one I got out tonight (after I managed to get the end of the extractor out with the welder). It removes 1 or 2 threads but there is still more than an inch of engagement back there on 8x1.25mm bolts. I'm hesitant to do a complete drill/tap solution to the same threads because the remaining portions of the factory stainless studs jams things up. That's how I broke the tap off in the EGR holes on the manifold.
 
Last edited:
Blue85 said:
Yes, I was planning to just run it. Interestingly rated at 440ft-lbs, same as the 8.1L. Burb/Av/XL and some vans with 8.1 came with 4L85-E, which is rated for 460, but most seem to think these are all under-rated. 5-speed Allison sounds interesting, but requires body lift, floor mods, extra controller, etc. The advantage of the Allison is lower gears down low (Allison 3rd is the same as 4L8x 2nd), but won't be much different on the highway. Allison .71 OD is arguably worse for towing than 4L8x .75.
Click to expand...

I have a GM Performance catalog that states that the 4L80E is rated up to 400 Ft. Lbs engine torque, and the 4L85E is rated up to 600 Ft. Lbs engine torque. If you install a billt steel forward clutch drum housing and a billit steel torque converter lock-up piston in a 4L80E this will bring the 4L80E up to the same 600 Ft. Lbs. pound rating as the 4L85E. I did that with my 4L80E.

852-34322-02k.jpg
 
Please provide some links. It's commonly quoted that 4L80-E is rated for 440 lb-ft and 4L85-E for 460 lb-ft and the biggest difference is the planetary set. By some definitions "80" means absolute max torque of 800 and "85" max of 850 torque, but these numbers are more commonly referred to as "relative" torque ratings, meaning a 4L80 is 33% stronger than a 4L60, 4L85 6% stronger than 4L80, etc. The 4L85-E didn't start until 2002, while the 8.1L was offered in 2001, so 4L80-E and 8.1 was a factory combo in the same basic platform I'm working with. 50% more torque from the '85 is not realistic, so that must be a quote from aftermarket parts manufacturers, which is not the same thing as a GM rating.

I just haven't found anything yet that motivates me to pull and rebuild my trans for the marginal improvements.
 
Blue85 said:
Please provide some links. It's commonly quoted that 4L80-E is rated for 440 lb-ft and 4L85-E for 460 lb-ft and the biggest difference is the planetary set. By some definitions "80" means absolute max torque of 800 and "85" max of 850 torque, but these numbers are more commonly referred to as "relative" torque ratings, meaning a 4L80 is 33% stronger than a 4L60, 4L85 6% stronger than 4L80, etc. The 4L85-E didn't start until 2002, while the 8.1L was offered in 2001, so 4L80-E and 8.1 was a factory combo in the same basic platform I'm working with. 50% more torque from the '85 is not realistic, so that must be a quote from aftermarket parts manufacturers, which is not the same thing as a GM rating.



I just haven't found anything yet that motivates me to pull and rebuild my trans for the marginal improvements.
Click to expand...

From Crate Engine Depot.

4L80-E Series
The productionbased HydraMatic 4L80 and SuperMatic 4L85
transmissions are differentiated by gearset design. Each
planetary gearset in the 4L80 has four pinion gears, while
the 4L85 has five pinion gears. The external dimensions and
mounting provisions are identical for each. The maximum
torque capacity for each includes:
4L80E – 440 lb.ft.
4L85E – 685 lb.ft.

The 4L80E has known weaknesses, and the factory lock-up torque converter piston and forword clutch housing are the main ones because they are made of cast iron. If you replace these two items with billit steel components the 4L80E will have the same torque capabilities as the 4L85E.
 
Last edited:
"SuperMatic" is their own brand name. It is not a GM transmission, but a modified transmission, as I proposed in my last post. The torque rating is from them and therefore can't be compared directly to GM torque ratings.

That number is above an Allison 1000/2000, so take it for what you will. Plus, I hesitate with pros who omit punctuation and publish "forword" and "billit".

http://www.crateenginedepot.com/Transmission-Supermatic-4L85-E-19300175-P10723.aspx

https://en.wikipedia.org/wiki/GM_4L80-E_transmission
 
Last edited:
Blue85 said:
"SuperMatic" is their own brand name. It is not a GM transmission, but a modified transmission, as I proposed in my last post. The torque rating is from them and therefore can't be compared directly to GM torque ratings.

That number is above an Allison 1000/2000, so take it for what you will...

http://www.crateenginedepot.com/Transmission-Supermatic-4L85-E-19300175-P10723.aspx

https://en.wikipedia.org/wiki/GM_4L80-E_transmission
Click to expand...

The wikipedia URL you posted states that the SuperMatic is a GM manufactured transmission all the way at the bottom.
 
I would run it. Toss on a cooler and keep it cool.
If you blow it up. Then hey, you need something stronger.
 
Wikipedia is only referencing the builder you linked! It looks like Chevrolet performance is using the SuperMatic name, but it's not the same thing as the regular production 4L85-E. Interesting topic..
 
You must log in or register to reply here.

Latest Posts

Top Bottom