I have fitted the Summit racing 8709 cam to my 2003 5.3 Silverado 2wd with a 4l60e, I am in the UK so Blackbear Performance remotely tuned the truck for me, I ran with the stock convertor initially then swapped to a Summit 700335 convertor, with a stall of around 2700rpm, this completely woke up the motor however I have been having issues with the convertor not locking up when cruising on the highway, as a result the transmission is overheating. Blackbear Performance have tried to increase line pressure several times however I am still having the issue and I can't use the truck as the i am going to destroy the transmission. I contacted Summit and they said that 'If the cruising rpm is at or below the converters stall speed its going slip. The only way to solve that is to install a smaller converter' this really confuses me as the only way to take advantage of the bigger cam is to run a higher stall convertor. Surely lots of people have encountered this, what is the solution to get the convertor to lockup at highway speed?

 

That converter is not enough for that high lift cam in my opinion. I also am curious why you choose that cam also. The specs say it comes in at 3500rpm-7200rpm.
I have a btr truck norris cam( which has a lot of dyno support numbers in our engines) in my 2000 single cab silverado with a 4l80e swap and stock converter, granted it is only a 212/22x .552 lift and 107 lsa. I should be running a 3400 stall a least. Torque comes in around 2500 rpms like it should for a heavier truck. As far as locking up you need to have it on a scanner watching live data to make sure it's doing what it's supposed to electronically. Could most likely be a bad converter.

 

Thanks for your input, if Im honest I naively picked the cam that gave the biggest power gains, Ive since realised that it is way too big and not really suited to what I needed the truck to do, I wish I had gone with the Truck Norris cam as Ive read a lot of good things about it since doing the swap, Ive bought an SUV as I needed transport so once the truck is fixed I will sell it, however need to get the issue with the convertor sorted as if someone buys it and does 20 miles on the highway it will definitely destroy the transmission, if I was keeping the truck Id go with a smaller cam however at this stage I just need it to get it running right.

As I am in the UK no one has scanners that work with these trucks, I sent a data log over to Blackbear performance and they have confirmed that the convertor is not locking up at all, I check error codes using the Torque app and I have the p0741 code logged, I have checked fluid levels and wiring to the transmission and it all seems fine, I reached out to Summit and they have agreed to replace the convertor although it means returning it to the US, this is good news although I am worried that something else is at fault and a replacement convertor doesn't solve the problem.

 

Just because it is a new part doesn't mean it isn't faulty. I've had a run of bad new parts especially over the past 2 years. Most likely it is the torque converter. Foxwell makes scanners that cover pretty much everything. I have a gt65 and it supports basically any foreign car out there. It's produced and sold out of china so support can have a little bit of a language barrier but every issues I've had they've had great communication. Also you could buy hptuners if you are planning on doing more ls stuff in the future.
Links for foxwell and hptuners.
https://www.foxwelluk.co.uk/ this is the uk site

https://www.hptuners.com/

 

Thanks for that, yes, I am beggining to think it is a bad convertor, Ill pull it off this weekend and return it, fingers crossed that solves it

 

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Greeting,
Rachel Gomez