I've got a 89 Iroc L98, 700r4. My transmission shifts at 5500 rpm which seems way to high for the engine. Its like my motor runs completely out of steam by 4500 and its fighting just to keep pulling up to the shift rpm. Is this normal or does something need adjusted?

 

You defininitely need to toss the TPI intake that's holding it back.

 

For your car, a WOT, 5500 RPM, 1-2 shift, is normal.

 

I never really run the car hard from a dig or slow speed but from what I have it isn't as noticeable as the 2-3 shift. It really falls off right before it hits 3rd.

 

My 700 will shift at 5500 at WOT from 1-2 also whether I manually shift or not. It's an Lg4, but torque still feels good at 5500. I would rather it shift at 4500, or when I decide.

 

5500rpm full throttle is normal. I have seen different magazine articles on stock thirdgens that have the full throttle 1-2 shift occur at 5500rpm. I know for the '85 LB9's the 1-2 full throttle shift occurs at 5500rpm and 2-3 full throttle shift occurs at 5000rpm, from what I have read. The cars I saw were also paired with the deepest ratio you could get on an '85 LB9 IROC, 3.42. That combination makes the car move very well.

You will want to have the full throttle upshift that high to make up for the wide percentage drops between the gears in the 700r4 trans. Once you start making intake mods or put on steeper gears and a high stall converter it will really make a difference.

 

For my Lg4 that's 500 into the redline. Seems a bit high. I thought redlining is a no no (except when racing).

 

You can take the LG4 up to 5500rpm without a problem. With the stock LG4 I wouldn't want to rev it past 5000rpm, the stock cam is not making power past that. After you make mods to the LG4, it may be worth revisiting the idea of changing the full throttle upshift points. The L69 engines had 5500rpm max tachs. The LG4 and L69 have the same rotating assembly with the exception of the L69 having flat top pistons instead of dished pistions. I think the L69 had a 9.5 compression ratio and the LG4 had 8.6 compression ratio. The LG4 won't have a problem seeing 5500rpm. The L69's had a hotter cam shaft that was capable of making more power past 5000rpm as well.

The LG4 and LO3 cars also got a single inlet air cleaner assembly. The L69 cars got a dual inlet air cleaner assembly. I'm not sure if the single inlet air box has a smaller pipe than one of the dual inlet boxes. The L69 style dual air inlet box is another item that would help get an LG4 or L03 motor better breathing ability.

The same can be said with stock TPI - that it doesn’t make too much power past 5000rpm. GM did set the upshifts that high on the TPI's though. The camshaft on the TPI cars that didn't get the peanut cam are able to support power to 5000rpm - 5500rpm. The stock long tube runner set up stops making power around 4500rpm. TPI is a torque production intake system, never was made to be a super high winding intake set up. That being said mods can be made to TPI to give it more breathing power up higher in the rev range.

The 305's and 350's that came stock in 3rd gens are 2bolt main blocks with a cast rotating assembly. They won't have a problem seeing 5500rpm. I wouldn't want to take them past 6000rpm though without upgrading the rotating assembly and getting 4bolt mains. Probably don't necessarily need 4 bolt mains for a 6000rpm street motor but I would rather be safe than sorry if you are going to wind it up there all the time. When I take parts out I usually put parts back in that are stronger.

 

Just FYI, the Lg4 got bumped up to 9.5 compression ratio in 85. Prior to this it was 8.6. The valve springs in the L98, and LB9 are stiffer cause of the better cam. I am more concerned with a sbc loosing a push rod through the valve cover cause the rockers may start floating. BTW, I make power right up to 5500. I don't feel the wall some hit at 4500. Maybe the engine is a little warm from the previous owner, or what ever. I would just like the choice of RPM shift points when I manually shift as I would with a stick.

 

Ahh I see. Is your transmission still 100% stock?

You could get a 5000rpm or a 5500rpm governor if you wanted to. They sell governor recalibration kits online that have different weights and springs to change the full throttle shift points. I never had any luck with them. The shift points would be either to high or to low.

When I got my new trans from Bowtie Overdrives I had them install a governor that would make all full throttle shift points happen at 5500rpm. They have other governors to with different full throttle shift points.

I have seen some after market trans companies install manual / automatic valve bodies to allow full manual shifting with no governor overide. With my new trans set up I really don't shift manually anymore.

http://bowtieoverdrives.com/catalog/...UBCAT&CATID=ZE

 

I believe the tranny is stock. I can tell the difference from my other 700r4's that are newer, or rebuilt and have been upgraded. The later 700's seem to be smoother when going from park to 1st, and a better 1-2 shift.

 

Yeah that sounds about right. I thought that the late '86 and the 700r4's after '87 got some improvements in the transmission that improved the shift characteristics.