so after doing some research i've discovered a problem with my conversion

99' ls1 to a power glide, ls1 was originally mated with a 4L60

i have a few separate issues

1. car actually idles and runs fine I haven't put any power through it to date, i have all gears and i have had it up on the transbrake to about 3000 rpm

2. when i was installing the setup I noticed the converter would float about 10-15mm from bottoming out into the transmission on one end and touching the flex plate on the other. I was a little sceptical of this but once i bolted the converter to the flex plate all seemed great and spun up freely with no issues

3. i randomly come across SBC adapters for earlier boxes and lose my marbles (haha), the list of questions i have regarding the spacer is as follows:



a) as far as i can see the spacer in my scenario will centralise the converter it will not address the float issue, but if i include this spacer i feel it will push the converter away from the flex plate (will have to confirm after measuring)

b) has anyone else come across this float scenario and is it a problem, e.g. could i snap the input shaft from lack of contact area, damage the pump from lack of engagement etc

c) it appears as if the best scenario would be to space the flex plate away from the engine which pushes the converter back towards the box (at a guess this would only be an option if the converter snout is currently seating into the flex plate)

d) if the spacer is placed between the crank and the flex plate does the start still have enough reach to engage the flex plate to crank?


This probably doesn't make a lot of sense but if anyone can lend a hand or some experience it would be greatly appreciated



Chris

 

Read the link in my Sig

 

The powerglide and the th350 are completely interchangable, I have a th350 on my 4.8. I used flexplate gm part #12621399 (elongated holes) flexplate spacer #12563532 and bolts 12563533 x 6. Hope this helps you out. Work awsome for me.

BTW... if there is any wobble it will beat the bushing out of the trans pump and score the convertor hub. Possibly breaking the pump and/or the convertor.

 

had a good read of that prior, the part that didn't make sense is the reasoning for the spacer in my case

i feel the need to have a spacer but ONLY to push the converter AND flex plate closer to the gearbox. I'll have to get some more information

appreciate the feedback

 

No, the spacer goes on after the flex plate and supports the hub. Think of the spacer as just an extension of the crank.

In stock form the 4.8/5.3L flexplate are dished to allow for bolting up to the converter, so the 4l60e has a longer converter hub that rides actually on the crank itself. Now the 4.8/6.0L used with the 4l80e (because that trans converter is spaced for the SBC motor it) uses a flat flex plate and the spacer goes next the the crank spacing it out the 4l80e converter hub is shorter and it rides on the spacer which then rides on the end of the crank. Some of the early 99-00 cranks actually were 10mm longer and used the flat flex plate.



If you place the spacer then dished flex plate it will not bolt up as the flex plate will be spaced 10mm from the starter teeth and 10mm to close to the trans itself and the converter will bottom out into the pump breaking it.

A cheaper alt. to the GM spacer and longer bolts is the hughes space bushing it rides between the verter hub and flex plate and has a lip that rests inside the crank http://www.summitracing.com/parts/HUP-HP3795/ It installs with no need to unbolt the flex plate.

 

ok so to clarify there are two seperate issues i was hoping to address

1 - that the snout of the converter must be supported to keep everything balanced, not a drama it goes inbetween the flexplate and the converter to achieve this. I can easily check this scenario by taking the converter and flexplate off and sitting the flexplate on top of the converter checking for clearance.

2 - i had what appears to be excessive play between the flexplate and the gearbox, e.g. the converter when bottomed out on the gearbox had about a 20mm gap between the flexplate and the converter, the logical solution to this problem would be to place a spacer between the engine and the flexplate closing that gap


if i was to use the adapter between the flexplate and converter i wouldn't be solving my issue of the 20mm of play as the spacers job in this example is to only centralise the converter not offset its position

i'll get some pictures up this weekend

 

The ls1 flex plate should be dished.

Check that your converter is engaged. It should be 28.5mm from trans bellhouse to converter pads.

 

ok i'll measure that when i get the box out, i've taken some photos










i can confirm the flex plate appears dished luckily i have a flate sfi flexplate i can use along with the spacer, just before i fit it i'm going to fit them while on the ground to confirm the converter isn't mounting into the flex plate (not sure what converter i have exactly)

the only thing this wont change and you can see it from the picture is the distance the converter is from the gearbox, can anybody check for me the distance to the seal to the start of the converter? i'd need the measurement when it's all installed in the car

cheers

 

ok another little update, once i took the bolts out for the converter it only slid back into the box about another 10mm max before it bottomed out

so i've ordered the spacer and bolts (got pumped $70us postage ) with any luck i'll have it all back together this weekend

much appreciate all the help

 

I just bought a 5.3 with no flexplate and will be mounting it to a powerglide. Is this the best option if starting from scratch?

 

he's spot on

the turbo 350/400 converters don't come with built in support bushes, if your using a 350/400 converter with a glide you need to have your powerglide bushed to suit

with regards to the spacers, i used a standard LS1 flex plate (has the dished centre) elongated the holes and used the after market lengthend high tensile bolts (use loctite sealant as the crank holes push through to the bottom end)

hope this helps