All about Flexplates, Converters, Transmissions and Spacers - LS1TECH - Camaro and Firebird Forum Discussion

Go Back  LS1TECH - Camaro and Firebird Forum Discussion > CHASSIS, SUSPENSION, APPEARANCE > Automatic Transmission
Reload this Page >

All about Flexplates, Converters, Transmissions and Spacers

Notices
Automatic Transmission 4L60E | 4L80E | TH350 | TH400 | TH2004R | Powerglide | Converters | Shift Kits
Sponsored by:
Sponsored by:

All about Flexplates, Converters, Transmissions and Spacers

Old 03-26-2015, 09:09 PM
  #1  
Moderator
Thread Starter
 
mrvedit's Avatar
 
Join Date: Aug 2010
Location: Ann Arbor, MI
Posts: 6,161
Default All about Flexplates, Converters, Transmissions and Spacers

When installing a different (non-stock) transmission there is often confusion over what flexplate to use and whether a spacer is needed. When swapping an LS engine into a custom Hotrod, there is even more confusion:
  • long versus short cranks
  • dished versus flat flexplates
  • whether the desired transmission needs a spacer or a pilot extender sleeve.
I will therefore try to clarify some of this. (Many thanks to Chris from CircleD Converters for explaining this to me, providing the crank pictures and proof reading this article.)

A key concept is understanding what is meant by "short crank" versus "long crank". The SBC, BBC and all GM engines before the LS engine had a crank which ended about .740" past the back of the block. This position of the crank with respect to the back of the block is now called "long crank". The LS engine was designed with a shorter crank, it is about .400" shorter than an SBC/BBC crank with respect to the back of the block and is therefore called a "short crank". (The LS crank only extends about .340 past the back of the block.)

Here is a picture of the short versus the long crank. (Both cranks were cut at about the position of the rear-most connecting rod.) Notice that the cranks have a lip of about .300" depth for mounting the flexplate.

Name:  60f9cd63-80e0-47ba-a36f-29e18810642c_zpsb16n0i4o.jpg
Views: 32098
Size:  257.3 KB

To add a bit of confusion, a few LS engines in '99 and '00 for truck applications were built with a "long crank"; I will detail that later.

Lets start with a stock Gen-4 FBody with an LS1 engine and 4L60E transmission. It has a short crank and a dished flexplate. While the LS crank is short, GM wanted the starter and converter in a "normal" GM position and therefore created a dished flexplate with a 0.575" offset. The LS-style 4L60E transmission has a 300mm input shaft (and a bolt hole in the 12 O'Clock position) and uses an LS-style converter. The 3 converter bolts are on a unique 11.066" diameter pattern, which is different from previous SBC and BBC patterns. The LS converter also has a longer (than SBC/BBC) pilot extending about .600" past the converter pads.

To install a different transmission into your LS1 F-Body, you need to know the bolt pattern and pilot depth of different converters. Here they are:
  • TH400 and 4L80E have a 11.5" diameter bolt pattern, sometimes called the "big" pattern.
  • TH350, 700R4 and LT-style 4L60E have a 10.75" diameter bolt pattern.
  • LS-style 4L60E have a 11.066" diameter bolt pattern.

The pilot for all non-LS converters extends only .250" past the mounting pads (versus about .600 for LS-converters).

Therefore, if you want to install a 4L80E in your LS1 car, you have two problems - the bolt pattern is wrong and the converter's pilot is too short. The solution is to install the GM spacer and a flat flexplate that has the 11.5" bolt pattern. The .405" thick spacer is installed between the crank and the flat flexplate, effectively making the crank act like a "long crank" with the hole for the pilot extended far enough to properly engage a 4L80E converter. The starter will also properly engage.

Here is a picture of the GM spacer part #12563532; you also need 6 longer bolts #19257940.

Name:  IMG_7722_zps8u7aixbv.jpg
Views: 30670
Size:  177.1 KB

And when it it bolted to a short crank, the combination is the same length as a long crank.

Name:  IMG_7246_zpsbzwdranr.jpg
Views: 31168
Size:  263.4 KB

In other words, to use a flat flexplate you need either a long crank or a short crank with the GM spacer.

Someone on a tight budget might be inclined to try to use the stock dished flexplate, drill new holes for the 11.5" or 10.75 bolt pattern and place the spacer after the flexplate (crank, flexplate, spacer). While this will bolt up properly, care must be taken to ensure that the spacer is properly centered by the lip on the crankshaft. (Details: The lip is .300", the stock flexplate is .150" leaving .150"; now subtract the .040" chamfer on the crank and .040 chamfer on the spacer and only .070" is available to center the spacer. However, sometimes the lip is less and/or the flexplate is thicker.) If the spacer if only positioned by the bolts and not centered on the lip of the crank, this may cause vibration and potential future breakage or problems.

Instead of using a spacer, a pilot extender sleeve can be used with a dished flexplate. It is not ideal; since the extender is relatively loose, there are reports of it causing noise. This is what the sleeve looks like:

Name:  IMG_0723_zpshtmfwnos.jpg
Views: 30392
Size:  194.0 KB

As mentioned, some '99 and '00 LS1 truck engines came with long cranks, a flat flexplate and a 4L80E transmission without a spacer. It appears that most (all?) LQ4 6.0l Vortec truck engine have the long crank; there are reports that some 4.8l Vortec engines also have the long crank. Obviously these long crank engines will bolt up easily to a non-LS transmission, but they cannot be used with an LS-style 4L60E unless a custom converter with a shorter pilot is purchased.

For those of you calculating the offset numbers, the OEM flat flexplate is .175" thick, plus the .405" spacer gives a total offset of .580". This compares with the OEM dished flexplate which is .150" thick and has a dish of .425" for a total offset of .575.

In the following picture a stock flat flexplate is on the left and a multi pattern dished flexplate is on the right:

Name:  IMG_0722_zps8rwjzotz.jpg
Views: 31178
Size:  206.4 KB

The following picture shows the flat flexplate sitting on a long crank (left), and the dished flexplate sitting on a short crank (right). Notice that the total offset of each combo is the same:

Name:  IMG_0720_zpstmrdejxg.jpg
Views: 30381
Size:  172.0 KB

A popular LS flexplate upgrade is the TCI #399753 which has a dual pattern to support both 10.75" and 11.066" diameter converters. While it appears flat, its thick design and and thick mounting pads for both the crank and the converter mimic the stock dished flexplate with its .575" offset. Due to its thick design it should not be used with the GM spacer because there is no crank lip left on which to properly center the spacer.

Similarly, the TCI flexplate #399754 is identical to the 753 except it is drilled with the 11.5" 6-hole pattern to support 4L80E converters. It is very thick and has the same .575" offset. To mount a 4L80E converter Chris recommends not using the GM spacer with it (no lip left to center it) and instead using a pilot extender sleeve.

Last, remember that a custom converter company like CircleD can build e.g. a 4L80E or TH400 converter with a longer pilot so that a spacer or pilot extender sleeve is not needed. Generally there is little or no additional charge for this.

Last edited by mrvedit; 04-02-2015 at 11:45 PM. Reason: More pictures
mrvedit is offline  
Old 03-26-2015, 09:45 PM
  #2  
LS1Tech Premium Sponsor
iTrader: (21)
 
Circle-D's Avatar
 
Join Date: Feb 2006
Location: Houston, TX
Posts: 2,471
Default

Great write up Ted, appreciate you taking the time to put all this info together. I know it will help countless enthusiast. We are here to help with any questions you guys will have.

Chris
__________________
Please fill out my Ask Chris form for converter recommendations.

http://i1288.photobucket.com/albums/...psd87ed8f5.jpg

http://i1288.photobucket.com/albums/...ps92fe0d92.jpg
Circle-D is offline  
Old 04-01-2015, 09:02 PM
  #3  
Moderator
Thread Starter
 
mrvedit's Avatar
 
Join Date: Aug 2010
Location: Ann Arbor, MI
Posts: 6,161
Default

The flexplate pictures above are of Circle D's "LS Multi pattern" dished flexplate which is both a nice upgrade from the stock flexplate and will bolt any short crank LSx to many GM converters. (You may need the pilot extender sleeve for some combinations.)
In more detail, it has:

6 Bolt holes for 4L80E and TH400 converters (11.5" pattern)
6 Bolt holes for 4L60E LS-style and 6L80E converters (11.066" pattern)
3 Bolt holes for 4L60E LT-style, 700R4, TH350 converters (10.75 pattern)

Hopefully my posts in this thread are reducing confusion and not increasing it.
mrvedit is offline  
Old 04-02-2015, 08:58 AM
  #4  
TECH Senior Member
iTrader: (96)
 
01ssreda4's Avatar
 
Join Date: Aug 2007
Location: Turnin' Wrenches Infractions: 005
Posts: 24,140
Default

Good info.....heres my contribution

Name:  ls-flexplate.jpg
Views: 29644
Size:  109.3 KB
01ssreda4 is offline  
Old 04-02-2015, 10:50 PM
  #5  
Launching!
iTrader: (1)
 
alowerlevel's Avatar
 
Join Date: Sep 2007
Location: South Jersey
Posts: 233
Default

Originally Posted by mrvedit View Post
there are reports that some 4.8l Vortec engines also have the long crank.
I can confirm this as the 4.8 I swapped into my 73 has the long crank, it was from a 2000 5 speed manual truck.
alowerlevel is offline  
Old 04-07-2015, 03:23 PM
  #6  
TECH Regular
iTrader: (2)
 
bboyxclub's Avatar
 
Join Date: Mar 2007
Posts: 410
Default

OMG This is gold!. Im getting to do my M6 to Auto Swap so your write up comes just in time! Awesome stuff man. THANKS

Sticky material if its not by now.
bboyxclub is offline  
Old 11-26-2015, 10:11 AM
  #7  
LS1Tech Sponsor
iTrader: (16)
 
Bob@BruteSpeed's Avatar
 
Join Date: Mar 2003
Location: Roanoke, IN
Posts: 20,855
Default

Any ideas on a Gen V LT1 with a glide? That's what I want to use in my Vega. Bob




__________________
ATI ProCharger and Moser Sales 260 672-2076

PM's disabled, please e-mail me
E-mail: [email protected]

https://www.brutespeed.com/index.htm Link to website

Bob@BruteSpeed is online now  
Old 01-15-2016, 01:24 PM
  #8  
TECH Resident
iTrader: (4)
 
dementia's Avatar
 
Join Date: Apr 2004
Posts: 882
Default

Same boat here going from m6 to auto. Have my 4l80e and was looking to do the mezier billet flex plate. Will this combo need an adapter to pair with an ls1? Converters an fti triple billet 10in.

Last edited by dementia; 01-15-2016 at 01:51 PM.
dementia is offline  
Old 04-24-2016, 08:14 PM
  #9  
TECH Resident
iTrader: (11)
 
Join Date: Nov 2014
Location: San Marcos, Tx
Posts: 971
Default

A little info added. I had an 02 LQ4 that I just sold the 4L80e trany and converter today. The crank is a short style. The flexplate has the spacer crimped onto it to compensate for the short crank.

Now here is MY question. Which flexplate do I need for a powerglide and 3 bolt converter to mate to my LQ4?
Taxman20 is offline  
Old 08-12-2016, 09:51 AM
  #10  
On The Tree
 
Join Date: Nov 2010
Location: St. Cloud, MN.
Posts: 114
Default

I'm getting on this a little late. I just picked up an LQ9 which has the flat flex plate and will be mated to my 700R4. According to what I just read, I simply need to get TCI flexplate #399754 and that's it? No spacer or longer bolts required?

Last edited by Ozz1967; 08-21-2016 at 08:54 PM. Reason: Removed the excessively long "quote".
Ozz1967 is offline  
Old 08-15-2016, 08:53 AM
  #11  
LS1Tech Premium Sponsor
 
Circle-D_Brian's Avatar
 
Join Date: Jan 2014
Posts: 324
Default

If you have the flat flex plate, you most likely have an LQ4, as the LQ9 came with 4l6x style dished flex plates. Assuming your motor is 2001+, you can remove the flat flex plate and the spacer behind it and run the 399753. It will come with it's own crank bolts as well as the necessary pilot extender to properly engage the crankshaft.

-Brian
__________________
Please fill out our Ask Circle D form for converter recommendations.
Circle-D_Brian is offline  
Old 08-20-2016, 09:58 PM
  #12  
On The Tree
 
Join Date: Nov 2010
Location: St. Cloud, MN.
Posts: 114
Default

Originally Posted by Circle-D_Brian View Post
If you have the flat flex plate, you most likely have an LQ4, as the LQ9 came with 4l6x style dished flex plates. Assuming your motor is 2001+, you can remove the flat flex plate and the spacer behind it and run the 399753. It will come with it's own crank bolts as well as the necessary pilot extender to properly engage the crankshaft.

-Brian
Ok, the junk yard is pulling the motor out of the truck this weekend and I should have it by next wednesday or so.I'll know more by then.
Ozz1967 is offline  
Old 08-21-2016, 08:54 PM
  #13  
On The Tree
 
Join Date: Nov 2010
Location: St. Cloud, MN.
Posts: 114
Default

Originally Posted by Circle-D_Brian View Post
If you have the flat flex plate, you most likely have an LQ4, as the LQ9 came with 4l6x style dished flex plates. Assuming your motor is 2001+, you can remove the flat flex plate and the spacer behind it and run the 399753. It will come with it's own crank bolts as well as the necessary pilot extender to properly engage the crankshaft.

-Brian
Also, I haven't found any LS swap cross members that "fit" the 700r4.
Ozz1967 is offline  
Old 12-04-2016, 01:59 PM
  #14  
On The Tree
iTrader: (1)
 
G-BODY-JAMES's Avatar
 
Join Date: Dec 2015
Location: Kelowna BC Canada
Posts: 123
Default

just found this thread i'm doing th4oo swap to my ls3 11.5 bolt pattern converter 3-4000 rpm stall
i have purchased the tci 399754 flexplate and couldn't figure it out with the sleeve spacer etc. (lost or threw out my instructions haha)
(2010 camaro ss 6.2 L LS3)
ok i found my issue.....well one of em haha so my engine was a manual trans prior to my swap and it had the pilot bearing installed preventing me from figuring out the spacer bushing piece with the 399754 TCI flywheel simple mistake haha and for the th350 trans i used the first time i simply bought a 6.0L flywheel and gm adaptor piece/bolts from the junkyard and ovaled out 3 torque converter holes so it would bolt up and she worked fine. the 6.0 L engine must have a 4l80 trans behind it for it to be the right flywheel for this. i was told but after reading this thread there may be more to it than that !!!

so i now have the new flywheel bolted up (399754) the flywheel simply bolts up as normal the torque converter centering ring/bushing/sleeve slides into the end of the crank freely before or after bolting up flywheel (did not have to hammer it into seat) and the torque converter snout fits snugly into that.

the trans and stall torque converter to flywheel/ block are going to mate up perfectly (measured) but when i tested the converter alone to see how far the snout penetrated the bushing it was not fully seated into it thus leaving approx 1/8" or more space where the bushing could walk outwards onto the TC. snout and that creates a situation where it wouldn't be penetrated into the crank enough anymore to keep the TC. perfectly centered.. and would most definetly vibrate/ be noisy or cause failure not good.
now even if the snout was longer on my converter there would still be that space of 1/8 " or so for the sleeve extender to walk out onto snout causing issues. or maybe not if it bottoms out on the centering sleeve inside lip..?? unless of course it was long enough to penetrate the crank itself but i already have the converter and paid cash so....
(need longer centering sleeve???? is there one???)

i think if i had a ring spacer to put on the converter snout prior to installing it to close this 1/8" or more gap it would work great or weld it to the TC. or weld it to the centering Bushing/sleeve (would be better less movable parts) just when i thought i had her figured out hmmmmm
if no spacer rings existed i thought of purchasing another sleeve bushing and simply cutting off the amount i need to make up and close that gap...

part numbers for spacer rings?? or i guess snout extender weld on rings??

what ya think? any extra info appreciated thx.

FIGURED IT OUT
got the centering bushing knearled to make it snuggly fit as to have no movement during operation and the 1/8 inch ish gap (between converter and bushing) is necessary as the converter gets hot and expands and contracts during use so im good here!!! only thing now is to test the starter gear engagement and make sure it is sufficient

Last edited by G-BODY-JAMES; 12-18-2016 at 06:00 PM.
G-BODY-JAMES is offline  
Old 12-15-2016, 01:38 AM
  #15  
Launching!
 
Join Date: Oct 2016
Posts: 248
Default

Ok so I have a 5.3 with a 4l80e with a yank converter made to fit the 3 bolt 4l60e converter... would this tci flexplate work for me ?
Ogoz23 is offline  
Old 12-15-2016, 08:47 AM
  #16  
LS1Tech Premium Sponsor
 
Circle-D_Brian's Avatar
 
Join Date: Jan 2014
Posts: 324
Default

I know TCI 399753 would work for you. I believe they also have a newer option that would be the 399853, but don't hold me to that one. I don't have any personal experience with it yet.

-Brian
__________________
Please fill out our Ask Circle D form for converter recommendations.
Circle-D_Brian is offline  
Old 12-15-2016, 08:57 AM
  #17  
Launching!
 
Join Date: Oct 2016
Posts: 248
Default

And with this flexplate I wouldn't need a spacer ?
Ogoz23 is offline  
Old 12-15-2016, 09:04 AM
  #18  
Launching!
 
Join Date: Oct 2016
Posts: 248
Default

Or longer bolts ?
Ogoz23 is offline  
Old 12-16-2016, 09:06 AM
  #19  
LS1Tech Premium Sponsor
 
Circle-D_Brian's Avatar
 
Join Date: Jan 2014
Posts: 324
Default

No spacer necessary. It comes with a pilot extender that you will NOT use. This flex plate uses thick washers to replicate the "dished" shape, you you will need the appropriate longer converter bolts. Probably 20mm under head length for your yank converter, but always check for proper thread engagement. It actually comes with new crank bolts too, so you're covered there.

-Brian
__________________
Please fill out our Ask Circle D form for converter recommendations.
Circle-D_Brian is offline  
Old 12-16-2016, 04:11 PM
  #20  
On The Tree
iTrader: (1)
 
G-BODY-JAMES's Avatar
 
Join Date: Dec 2015
Location: Kelowna BC Canada
Posts: 123
Default

Originally Posted by Ogoz23 View Post
Ok so I have a 5.3 with a 4l80e with a yank converter made to fit the 3 bolt 4l60e converter... would this tci flexplate work for me ?
To make sure I'd suggest messaging the TCI tech they walked me through all the exact stuff to check and I have the proper flexplate (399754) it's for short crank LS with a 11.5 inch torque converter bolt pattern
on my th400 I will be using the centering bushing provided being that my converter wasn't fabricated with a long snout to mate directly to the crank pilot hole
note!!!! The bushing TCI provided would slide in and out of pilot hole by hand, you do not want this as it will walk back and forth causing vibrations, noise other problems I had the end of the bushing that inserts into the crank pilot hole Knearled so that it will press into crank per say and used sleeve retainer thus not allowing any movement of the bushing
the knearl process gave me about 3-5 thousandths
tapped into crank using piece of wood BAM!!!

my 2 cents
G-BODY-JAMES is offline  

Thread Tools
Search this Thread
Quick Reply: All about Flexplates, Converters, Transmissions and Spacers


About Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

© 2018 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: