My '69 vert currently has the numbers matching 350 2bbl mated to a 2-spd powerglide, along with what I believe to be is a 2.56 rear end (don't know what else it could be). The car is sadly slower than my Honda Pilot.... My friend with a TH400 is switching to a 2004r and is selling me the 400, and I'm seeking information about the swap and what I'd need. First of all, what rear end do you think would best fit my combo? I do mostly city driving, and as it's setup currently it's a complete dog. I don't expect much from a bone stock 350, but it's all noise and no-go Don't want another open diff, one wheel peels are pretty lame. Now for the tranny, does it just bolt right up? What about the cooling lines? Also, I've seen many people running conversions with floor shifters, but how will it work with my column shifter? Last thing is the drive shaft, do I just have to get new yokes and have it shortened? tl;dr: - What rear end should I use? - Is the TH400 a bolt on conversion? What do I need to make it work? - Does drive shaft need shortening with new yokes?
Yes, the th400 will more or less bolt right up (if out of a '68 or '69). Yes, you will need to shorten (and balance) the driveshaft. The trans lines will need to be modified (just put in new ones). The shifter connections will also need to be modified, I put in a shifter from a 400 car, problem solved!
I don't think changing gearing or rear end would change much. The trans change will also not change much, other than better gas mileage.
The biggest change would be putting a 4bl and better heads on the engine. If it's a 350 2bl, it will still be a 350 2bl with the changes you are mentioning.
PS, you don't say what year the th400 is, but if from the '70's, you will need a whole bunch more mods, plus you will lose the electronic kick-down capability. What you are proposing could cause a lot of heartburn, trial and error, and you still won't be able to lay down two lines of rubber. At least with the th400, you will get a little better gas mileage, unless you have a lead foot.
I used to be indecisive. Now I'm not sure. I feel like I am diagonally parked in a parallel universe. 1968 400 convertible (Scarlet) 1976 T/A - 455 LE (No Burt) 1976 T/A New baby, starting full restoration. 1968 350 - 4 speed 'vert - 400 clone (the Beast!) 1968 350 convertible - Wife's car now- 400 clone (Aleutian Blue) (Blue Angel) 2008 Durango - DD 2008 GXP - New one from NH is AWESOME! 2017 Durango Citadel - Modern is nice! HEMI is amazing! 1998 Silverado Z71 - Father-daughter project 1968 400 coupe - R/A clone (Blue Pearl) (sold) 1967 326 convertible - Sold 1980 T/A SE Bandit - Sold
I'm not quite sure what year the trans is from, but here is his '68 setup quoted from a Hot Rod Network article: "The 462 outputs power to a TCI Saturday Night Special 2,000 rpm stall converter connected to a Turbo 400. A B&M trans cooler provides extra protection and shifts are handled by a B&M Quicksilver unit. The stock driveshaft connects to a GM 12-bolt with Moser axles and an Auburn Pro Series carrier housing a Richmond 3.42:1 gear set."
He's running a 428, also not sure from what year. I will ask him and see. So you are saying if it's from the 70's I shouldn't go for it?
Also now that you mention the heads, I was thinking of going two routes for the 350: swap heads, intake, carb (quadrajet or holley?), and cam for a high comp OR doing something a little more adventurous with just an intake and larger carb, clean the old heads up, and run stock compression with some forced induction (high compression and forced induction don't mix lol). I'm familiar with turbos and know what I'd need to make it happen, just would have to go through fabrication hell and back with the manifolds for a single turbo and intercooler piping, and have it tuned properly to avoid detonation... anyways that's to decide later. I just want to get a tranny and rear end setup that would suit me for the life of the car.
Not for sure but I think the flex plate will need to be changed. and a torque converter if it doesn't come with one The cross member will need to be changed to the 400 cross member, and trans mount You will need to get a drive shaft yoke for the 400 trans, and have the shaft shortened. Be careful on the yoke as there are two different size outer diameters, it will depend on the trans as to witch one you need. as far as the shifter goes. You can put in an after market floor shifter, or if you want to keep the column shifter, there is a company called Shift Works that make parts to change over to the 3 speed from the 2 speed shifter. http://www.shiftworks.com/index.html you will also need to run a vac line from the motor for the vac modulator. the cooling lines, you can run flex hose for it. I have been running rubber lines on mine for many many years with no problems, just make sure it is for transmission cooling. Or you can run steel braided. you don't have to run the electric kick down if you don't want to it will not hurt anything,
If your buddy is going the 200 R route see if he will give you all the stuff for the 400, as he will be changing most everything you need for the 400. Also you will see a little bit more quicker off the line as you have an extra gear. but the 400 uses more horsepower. On the drive shaft. Since you say your car is a numbers matching, I would see if your buddy is going with a new drive shaft on his and if so see if he will sell you his. if not then I would get a new one made for the 400 swap so you can keep your original one with the trans and everything else you change, so it can be put back to original if ever need be
on the rearend, you can install a posi unit and gears into your housing. I have 3:43 gears in mine with a TH400. It is ok for both town and highway. I have tall tires and turn around 2500 RPM at 65 MPH
If you really have a 2.56 or similar “highway gears†then going with numerically higher will make a big difference in acceleration. 3.23 or 3.55 would help a lot. You’d be turning some revs on the highway though. There are trade offs
I had a 350 2bbl with a 2sp Powerglide and 2.72 rear diff.
NOT a fast car to say the lest ...
2bbl Rochester is a good carb but 4bbl will get it going providing you get better rear end. Lower gearing (3.xx) will help you out on the low end but reduce your high end.
TH004 is good tranny but it's not going to "rip" your tires.
If you start changing the engine (heads) your probably going to go further (ie. change cam). It would be better to plan what your needs are and budget before "opening up the patient".
IMO I would be to try swapping out the tranny and rear end. Least costly and scope of change. No matter what you decide later for improvements, your decision on the tranny and rear end will work for you for any other mods.
You should be able to get a driveshaft without shortening your current one. Your linkage for tranny to steering column should work or getting another one is not hard to find. You need a downshift (electric) kit is available and you may need a vac line to tranny.
I have a 69 TH004 tranny out of a 69 Firebird. It's a complete tranny but I have no idea as to the condition so I would call it a core.
I need a 68 Firebird rear end with 2.56 /w SafeTrack.
If your rear end matches my needs I would be willing to swap or you could buy my core. At least you will know you have the correct TH004 for your car.
Engine Test Stand Playlist: https://www.youtube.com/playlist?list=PLwoxyUwptUcdqEb-o2ArqyiUaHW0G_C88 restoring my 1968 Firebird 400 HO convertible (Firedawg) 1965 Pontiac Catalina Safari Wagon 389 TriPower (Catwagon) 1999 JD AWS LX Lawn tractor 17hp (my daily driver) 2006 Sequoia 2017 Murano (wife's car) 202? Electric car 203? 68 Firebird /w electric engine 2007 Bayliner 175 runabout /w 3.0L Mercuiser__________________________________________________________
Thanks for all the input, and sorry for the delayed response (I don't check here as often as I should). Doug still insists that his tranny bolts right up to the block, which may be true, but it's looking like a lot of other parts will be necessary to make the swap happen. I'm really keen on swapping out the tranny and rear end and keeping the numbers matching parts for the unforeseeable future, so I don't think I'd want to give up my 2.56 (sorry Gus!). I think I'm going to get Doug's TH400, despite the possible complications presented, and see what other supporting parts I could get from him. He lives very close by so it'll be fairly easy to transport and work on the car. I guess it's going to be one of those projects where I order parts as I go lol. Better that I know all of these things now before I start!
Now MPG and revs for highway speeds were brought up, and I don't know if I really care about both right now. Again, I don't do a whole lot of highway driving (usually just once a month to cars and coffee) so if I wanted to get good mileage I'll just drive my Honda...
What specific rear ends should I start looking for? I know first gen rear ends aren't exactly the easiest things to find and I could be stuck modifying the wider second gen which isn't ideal... Anything in the 3.22-3.55 range would probably do fine, just looking for POSI and relative ease of installation. As Wade mentioned, I could put a POSI unit and gears into my housing which sounds like a good idea, I would just have to know that it could be put back together in it's original 2.56 state if I ever had to. If that is true, I would be very interested in that idea.
If you install the posi unit and gears into your housing , just save what you take out, you can reinstall it when ever you want. If you really want to change to a different housing, I would look for an 8.5" rearend out of a 72 and up Nova, Ventura, there are others but not exactly sure what others. They are all most as strong as the Chevy 12 bolt, GM used these to replace the 12 bolt , and you can find them pretty cheep, and they bolt right in, but the driveshaft has to be shortened, but you are going to have to do a different driveshaft anyway. I have one in my 69. Your car is the same color as mine was from the factory, do you have green interior also? mine has dark green deluxe interior, came with a 350 2 bbl TH400
Not quite what you were asking for, but here is a table that shows which gears our cars would have come with from the factory: http://thefirstgensite.com/library/axle/firebirdaxle.jpg A 69 with 350 2bbl and automatic trans is said to have had 2.56, or 2.78 if equipped with A/C.
There is also a "Mountain performance option" that would have given you 2.93 or 3.08, but I think that was a quite rare option.
Yes Wade, the car has a dark green interior with green carpet! I can take some pictures and upload them later... And the TH400 is coming out of a highly modified '68, you can read up on his build here: High Performance Pontiac - Hot Rod Network
It's quite the beauty, he also has a company called Billet Rides (Billet Rides) which fabricates various parts for first gens. It's quite strange how I met him considering how rare first gens are these days... He saw my car in the grocery store parking lot and was like "It's not everyday you see a '69 Firebird convertible!", and continued to show me his website and pictures of his car, and came to find out he was a mile away from me small world...
I'm set on the posi unit and gears, where would be the best place to source these and which ones should I look for specifically? And just to confirm, I'd still need a driveshaft if I kept my stock housing?
Nice. I haven't seen very many with Green interior Yes you will still need a different driveshaft. I see his car has a Chevy 12 Bolt rearend. See if you can get his driveshaft and crossmember with the trans. You might have to change the rear U-Joint to fit your yoke on your rearend. If he has a shop and does all his own work, I would talk to him about installing the posi unit into your car, he should know which one and where to get it from.