Technical '64 Impala Trans Swap

Hi gang,

I've had this Impala for about 27 years now, it's had three engines in it during that time, all small blocks, factory 283, then a 350, and now a 327. I've never rebuilt the original powerglide transmission but it's been slightly leaky for a good long time now and I park it over a drip pan in the shop. I've replaced the pan gasket but that didn't solve it, and it's hard to tell where it's coming from. Finally today I pulled the faithful powerglide out and I'm debating rebuilding a TH350 that I have and installing that in its place to go from a two speed to a three speed. There are several differences including length (350 is just over 2" longer), shift linkage, kick down (cable on right side vs. linkage on left side), output shaft spline count (driveline length and yoke change), vacuum pod on right vs. left, cooling lines have hose and clamp fittings, whereas powerglide has threaded hard-line fittings (would have to cut existing and install soft hose jumper) the fittings come out of the trans case in slightly different location and angle so it would be hard to swap fittings and make this work with existing lines. I think speedo hookup and dipstick are close enough to work with but anyway a few things to adapt. Plus perhaps column indicator and things I'm not thinking of yet...I need to check cross member mount location too haven't really looked at that yet.

I'm looking around to see if I can find a walk through of anyone performing this swap but haven't come across it yet so looking for input on anyone with that experience. I feel like it would be a decent perk having that kick down gear that the TH350 has over the two speed powerglide but hard to say if the mod will be worth it. It has always driven fine but it lacks that 45-55 range passing gear that I think the TH350 would offer.

I am going to look into parts availability on rebuilding as well which might affect my decision on which one to go through.

 

my 1967 el camino had a pg and I put a 350 both were same length and used same rear mount shift linkage and drive shaft didn't hook cable up it is only for kickdown.

 

Beautiful car, how about a 200 R4 same length as the glide and overdrive for interstate cruising

 

The early Aluminum Powerglide is shorter and has a different output spline, compared to the later 60s PG. So he has to change the driveshaft yoke and shorten the driveshaft regardless which trans he uses.

The dipstick and tube are different on the TH350, too.

You don't want to use that braided hose kickdown cable or dipstick tube...really....

Having 3 speeds is nice. Then again, gasket sets for the PG aren't hard to find, and if the transmission is working ok, you could probably reseal it for under $100 and be back on the road. Might want to change a few bushings and inspect the friction material though, that could add a little to the expense.

tough decision. I put a 350 in place of the iron PG in my brother's 58 wagon years ago....

 

An aluminum Powerglide in stock configuration is the simplest and cheapest automatic transmission to rebuild. .A monkey could do it given three tries.

 

Thank you for that correction.Then a 2004r would be a nice addition.

 

I'll say this...years ago, when I replaced the 'glide in my '68 Impala with a TH350, the extra overall gear ratio with the 2.5 low (give or take) as opposed to the 1.76 low of the two speed made it feel like it just gained 50 horsepower.

 

That's interesting, must be different generation trans as mine, these are definitely a couple inches different in length and have several differences, including spline count on the output.

 

I thought about something like that too, but I don't already have one haha. I might consider it depending on what I'm looking at with these two.

 

Great points, appreciate the thoughts on that. Why are the cable kick down and dipstick a no-go, do they not hold up well over time? This TH350 was in a friend's 39 Ford that had a Chevy stroker small block in it. That's why it has the cable stuff on it I'm sure I don't even remember if it was in working condition but I believe it was. It's been sitting for 25+ years so I'm sure it needs to be gone through. I'll be looking into those parts costs for both and see where it lands me. Also going to get together with a friend who works on these things and see what his thoughts are between the two, not much to see without having driven the TH350 so maybe we'll crack into them both and see what's to see.

 

Haha! Good to know and good news for me!

 

That would sure be a nice addition to this car. Looking at going through the engine again or buying a crate engine as well. I'm having trouble heating up, just drained it down and pulled the thermostat. Looks fine but who knows. I might yard out the water pump and take it apart too and see if there's something off with that. If that's not it, I might install a larger diameter fan that fits the shroud better than the one I'm running. 4-core radiator too so I'm not too sure yet what's up. Head gasket blockage? Hot light came on today idling out in front of the shop for 15 minutes, foggy windows and steaming out the overflow so pretty warm. Dieseled along for a few seconds after shutting down too so I've got some stuff to do. Carb needs work, all things I need to get around to.... It's been neglected a while.

 

I used to do them years ago for people, I had a stack of blown up ones next to my dad's garage, probably qualifies as a Super Fund site... a quick and dirty "front job" would get a tired one going again.

 

The braided dipstick tube is very small inside diameter, it's a nuisance to fill the transmission. Aside from how "street rod" it looks. The cable can be made to work, again it looks totally out of place on a car that fits this forum...I'd rather use the OEM cable. Some guys just don't use the cable at all, which you can get away with on a T350, since it only does the kickdown function. I like having a cable, myself. Although it's been a long time since I had a Th350 in anything of mine.

 

Swapping a T350 for a PG is one of the most common swaps. But since you would need to do a few more modifications to make it work than later PG (which is nearly bolt in and go), plus your T350 is sort of unknown shape since sitting for a length of time, I would consider the 200-4R. What rear gear does your car have now? If 3.70 or higher then the OD trans will definitely be nice. If rear gear is 3.55 it is kind of toss up, how much high speed freeway driving do you do? If taller than 3.55, then the OD will not work as well. The OD is really nice if you do some longer trips. Even a 700R4 will fit and work, but it is physically bigger than the 200-4R and slightly more modifications to make it work. The 200-4R is a good small block OD trans, that with some simple upgrades when rebuilding can handle as much power as you will ever put in front of it. Many of them are both Chevy and B-O-P-Cad bellhousing bolt patterns. Either 200-4R or 700R4 will require a throttle valve cable that must be hooked up and set correctly for proper and long term trans operation. The throttle valve cable is not hard, and sort of functions as both the kickdown and the vacuum modulator functions. No vacuum hookup on the OD transmissions.

I guess it depends on how much work and how much expense you want to do. Quickest, lowest cost and same driving is rebuild the PG and put back in. Most time, higher cost and better driving is the 200-4R OD conversion. T350 is in between those options.

 

I went from a cast iron pg to a TH350 in my 62 Bel Air 12 years ago and it still works great. I was changing engines too, but ended up just modifying all the existing stuff to work. The column shift linkage was easy to change, the driveshaft was easy to shorten, and you just need to get a different yoke.

The power glide was cool but the TH350 is way better. Cooler lines are easy to adapt. Nothing in the swap was a big issue really.

 

Yea that's a good point on the fluid fill as well as the appearance. They do look off with the braid. The engine bay on this car is going to go back the other direction too, probably some stock script painted valve covers, etc. to get it looking right. It's been a long time since this car has seen much attention that way.

 

Yea man I like your points here. @Tickety Boo was speaking to that OD trans too, I'll have to dig into the expense between options and see what makes sense. I'd have to source one to rebuild or turn in for core, or buy one ready for install. I'm almost leaning towards just cleaning up the PG and reinstalling due to ease but not sure yet. I don't drive too crazy far but it cruises the highway just fine at 60-70. And that's just it, it's a cruiser, we don't get into it and make like it's a muscle car, just drive it pretty low-key. If I look at an engine swap and go for HP it would be a different story but I'm not there yet with this car. I think I want to go retro originality looking with the 327 and dress it out like it was back then. We have other cars to beat on, burn out, bang gears, etc...lol so I guess this get's my fix on laid back cruising. Honestly I'm not sure what gear set it has, I'll have to check that out but it's fairly tall. If I bury my foot in it on the onramps I can pretty much hit 60 before the PG hits second gear. It's always driven fine, but I have had times it would be really nice to boot on it on the highway and have that intermediate passing gear. Almost a nice safety feature too. Kicking down that PG at highway speed, or close to, makes that small block sing! I do love a 327....

 

That is one killer bubble. I like 4-speeds too and have a couple hanging around in the shop. I have a rebuilt Muncie M-21 complete and ready to go that I pulled out of the 65 El Camino we have when we swapped to a modern Tremec 5-speed in that car. With the 64, I think I have a hard time not going full SS conversion with buckets, console, interior package and SS trim if I go the 3-pedal route. I know they made a few limited option go-fast cars those years that ran bench/stick but I don't know how common that was and it might not fit with this one. I almost cut it in and went that way a few years ago but decided against it. I think I would prefer to have either the bench/column or the buckets 4-speed, either going full SS clone route or keeping it standard hardtop. That's a tough one. Something about throwing my arm over the back of the bench seat with my bride by my side you just can't get in a bucket seat 4-speed car, ya know? hahaha.

That 4-speed/bench setup looks great in your 61. My El Camino runs a factory bench frame, but we bolstered it so it has kind of a bucket/bench combo look to it. I love that bench/stick look. The El isn't a HAMB friendly build in pretty much any way so it won't show up around here lol but it sure is fun to drive with a hot 454/5-speed/12-bolt posi. bright blue, 4" cowl, ghost flames and all kinds of billet. haha don't puke....

 

I'm curious, did you hard line thread your cooling lines or use hoses? This TH350 has clamp nipples for sliding on a rubber hose and hose-clamping. My PG is hard threaded into the body. I can cut and flare the factory cooling lines and run a jumper hose, or get new lines and go that route, I don't think I can make them fit as they are with the different orientation of the fittings and the angle they come out of the case on the TH350. Any change of getting pictures of your cooling lines and linkage, maybe the trans mount too?

 

We used the existing lines and just jumped to the trans with rubber hose.

I could grab some photos, but it won't be for at least a month as my car is in cold storage behind an ice-frozen gate. My car is too low to get photos of the underside without getting it up on the lift in the garage.

Mine was a cast iron powerglide, not sure if the linkage was different as a result.

 

Turbo 350 trans itself bolts in. You might be able to use the dipstick tube, I don't remember. The only thing I couldn't do myself at home was the driveshaft. So I bought one for 35.00 at a swap meet a column shift rod is available aftermarket for cheap. Cooler lines adapt easy. I pulled it later and dropped in a 4 speed. Powerglides are simple, but the extra first gear of a turbo 350 is hard to beat. Note this was in my 59 El Camino, very similar to your 64, and my 66 C10.

 

Gotcha, no worries man, it'll be pretty straight forward to sort out, I'm sure there are a lot of photos out there, I'll dig in and see what's been done. Otherwise I can come up with a good setup I'm sure.

 

Yea right on, sounds like it went off without a hitch then. I like that the Chevy bells are all more or less same-same, that sure opens up options. I'll have to look at the aftermarket column shift rod option and see how that looks. What is the application you used, or what was that source? I'd be interested to check that out.

I have a local drive shaft guy that has been through several drive lines for my, this two-piece needs to be refreshed anyway (X-frame). The carrier bearing support rubber is pretty cracked up and I think I'll just have it shortened with a yoke swap, new joints and rebalanced if I go the TH350 route. Cost usually isn't too bad on that. I had him rebuild the 2-piece for my Cummins Dodge truck and he told me the Mopar spec was to balance within 5 grams, and he balanced it within a half of a gram. I didn't fact check that but it sounds good to me, and he did a badass job, painted it, the works.

 

on the torque converter....beware there are two sizes bolt patterns for flex plate to converter. The later flexplates have both patterns, early ones might only have the large pattern. Check before you install the transmission, you may have to drill holes or swap flexplates. Keep the large diameter, just get one with dual converter bolt patterns if needed.

 

I bought the Shift Linkage rod for my 59 from Cars inc, it was listed for a 700 r4, for a 58-64 Impala.. on the 66 C10, I used the stock components with a little tweaking. I didnt go with the driveline shop because they were too far away. my cheap driveshaft looks to have been done at home, and not clocked properly, so I would reccomend a shop. Its worked for 20 years, so i cant complain too much. I ought a spare, just in case last fall. still, 35 bucks at a swap meet.

 

Good tip, thanks!

 

I looked around on carsinc but wasn't able to locate that linkage. I'll shop around and see if I can bring anything I find to the table here for others to see as well. Not 100% sure what route I'll go still but I'd like to get a complete idea put together of the swap either way.

 

Great thread.

I've had my '64 Impala for 35 years. I swapped in a low mile '61 283 4bbl cast iron powerglide 30 years ago.