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This forum has helped me a ton through out the process of building my car, and I'm in the middle of a swap from the th350 to a 4l80e. So far the th350 is out, and the 4l80e is bolted up in place. Here's my questions..
I had a energy suspension poly mount on the th350, and it fits the bolt holes on the 4l80e. Any reason I can't use this thing? It's pretty new.
I've got the back of the trans supported, with the cross member out. It's clear that I will have to modify the cross member to mount to the 4l80e. When I take my measurements to modify the cross member, is it imperative that I have the same height from the the floor to the yoke on the 80e at the same height the yoke on the differential? I guess I'm referring the drive line angle?
speaking of angle, what about side to side as well?
It is wise to try to duplicate the same dynamics as what GM designed. Using a level and also a laser pointer may help to make sure you get it where it needs to be....But I usually do all of this when the old transmission is still in the car. Especially if I am having to make my own crossmember or modify the facotry one.
I learned something from a guy who called himself 427swede that there are two ways to minimize vibrations in the driveline. The one everybody understands about equal and opposite angles and another possibility about equal angles called the W-arrangement. After a bunch of measurements I ended up doing the latter by modifying my differential carrier bracket to change the differential vertical angle alignment in the frame. I thought I posted that mod but couldn't find it just now.
Also the motor is offset in the frame so there is a side-to-side angle to be considered. Turns out that makes it a three dimensional problem if you really want to get into it.
As DUB says, you want to duplicate the factory setup as much as possible and if that is not possible you want to get the angles as close to equal as you can.
So from what I can gather from that thread you posted is that there is an intentional angles side to and the up down needs to be the same right?
any thoughts on reusing the mount as well?
You say you have to modify the crossmember but you don't say how. At this point you might just jack it into the position you want and measure the angles. It's not that hard to do given that you have some sort of angle measurement device. I really can't guess at what's going on here but if the distance from the mounting flat on the 4l80e to the centerline of the transmission is the same as that of your 350 it is hard to see that you have a problem.
Doesn't the driveshaft tunnel have to be modified for clearance to install a 4L80 transmission in a C3? And, if you don't do that, I think you get into shaft angle problems.
It looks tight, but the with the yoke on the back of the 4l80, it seems to clear. If I don't move the motor, wouldn't the end of the 80e be on the same side to side plane as the th350 was?
As you know the 80 is longer and this tends to carry the tail shaft deeper into the narrowing of the driveshaft tunnel. I had to do a small "ding" with a ball peen hammer on my steel floor tunnel to clear the yoke...about a 1/4" clearance was needed. You can re-use your mount if the holes line up for at the tail housing....can't remember if they're the same. Don't forget your pulley bracket for the emerg. brake. I created some shims to elevate my trans to go between the mount and the cross member...lowered/thinned the snub bushing on the pinion mount at the diff. The cross member in mine is bolted to all 6 of the factory locations...the fabbed cross member is primarily different in the mount location.
2" x 2" x 1/4" wall stainless....you're not going to be able to build from my tape measures.... you need to get the trans installed and determine critical points. I used a 1/4" piece of plywood to locate frame bolts, trans mount bolts, & parking brake pulley....you can see it in the back ground of one of my pics. Also, I later replaced the pictured trans. with a 1997 and up model 4l80e with sleeker pan and a relocated center hub lubrication cooler line.
Jim
Last edited by jimvette999; Feb 23, 2017 at 09:06 AM.
Something nobody here has addressed is the location of the air filter. Here is why. I live in Oklahoma, and our Oklahoma summers tend to be....er....warm. Scratch that. It gets hot as hades here. This also may come as a shock to us "old school" carburator guys, but with the switch to a modern powerplant, one thing overlooked is a thing called "cold air" and why it's important with these swaps.
I know many here are puzzled because they have done the swap and their car runs fine.....or does it? I learned the hard way, as my build egan as an LQ4 block, LS3 heads and morphed into an LSA supercharged engine jammed into a 74 Roadster.
But on a hot summer day things were taking place under the hood I wasn't aware of, and here is why.
On a hot 100 deg day, you can bet the underhood temps are quite a bit warmer, wouldn't you agree? But by how much? You think it might get 150 degrees under that hood? Mayber higher? Let's be conservative. How about 130 degrees? That's not too hot is it? Not only that, but your car survived over 40 years with a 14 inch filter drawing air from the middle of the engine and it ran great, right?
The problem is you didn't have an IAT sensor, and now you do. Why should you care? Because this little sensor sniffs the intake air temp of the air before it enters the engine, and is tied directly into the engines PCM timing control. As soon as the IAT's hit around 130 degrees, the PCM starts pulling timing. You get around 150 deg IAT's and your engine may have 6 to 10 degrees of timing being pulled and you don't even know it's going on bebind the scenes.
You MUST be able to not only draw air from in FRONT of the radiator, you need to be able to have the IAT measuring OUTDOOR AMBIENT air, and not engine compartment air.
I'm currently in the process of designing a cold air system that will draw filtered air from in front of radiator/condenser, and do so without having to horozontally shrink the radiator and AC condenser. Would love to hear your ideas!
4l80e swap progress, need help.
