# reviving old tranny thread - advice on converter stall speed



## ylwgto (Oct 27, 2009)

I'm reviving this thread...









Gear Vendor OD on a Th400, advice on tranny rebuild


My TH400 is a tired tranny last rebuilt in the late early 2000s. Been a great tranny, but recently it's flaring a bit in 3rd and the shifts are just not as neck-jarring at WOT as they used to be...I miss tire chirping. I've been battling with kickdown and short shifting woes for months (may not...




www.gtoforum.com





...because summer is here, I'll be in CA in a week and I do not want to drive my car with it's current tranny for another minute.

I've abandoned an OD conversion or manual conversion for now (can't afford it), but I am close on a local deal for a BOP TCI Streetfighter TH400 to replace my current one, direct swap. Given the price it seems cheaper and faster than a rebuild. Seller will guarantee the tranny in writing (my kind of seller) as it is low mileage as he made the leap to a 700r4 on his GTO. I will likely buy it, but it does not come with a torque converter. I will have a shop do the instal to ensure no issues with this "guarantee".

*Questions I need advice on:*

1. What stall converter should I be looking at and what are good brands? I know not to cheap out on a converter. I have no recollection of what I currently have. Engine is a mild 400 with speed parts, but nothing crazy. 3.25 rear. mostly round town fun driving with little highway time. I like ratchet shifting and chirping tires.

2. is there any variability in speedo drive units year to year on these transmissions or is it all standard (I want to reuse my current one)

3. I'm currently running the lines to an integrated cooler in an aftermarket, fully shrouded aluminum radiator. Is this sufficient or should I go back to an external trans cooler (always hated the way the soft lines look going under the radiator core support)?

4. any benefit to a poly trans mount over the standard style?

5. for a tranny shop this should be no more than a 3hr job including a pan drop to put a new filter and fluid in. That sound reasonable?

6. anything to be done about my weepy rear main seal without dropping the oil pan (wishful thinking here I imagine)? I am going to photo the back of the crank to make sure it is cast to receive a pilot bushing for my manual conversion someday.

Thanks. I feel so close to crisp, high RPM shifts again


----------



## armyadarkness (Dec 7, 2020)

The entire TC purchase would be based on quality and cam RPM. If you don't know what cam you have, then just get a good converter and a mild stall. When I was originally considering that route, I had the names of the best companies to go with, but that was a year ago.

If no one else chimes in on it, the info is in my old threads, so we can always go back and find it.

For the record, we had my TH400 disconnected and out, in under an hour, in the driveway.


----------



## ylwgto (Oct 27, 2009)

armyadarkness said:


> The entire TC purchase would be based on quality and cam RPM. If you don't know what cam you have, then just get a good converter and a mild stall. When I was originally considering that route, I had the names of the best companies to go with, but that was a year ago.
> 
> If no one else chimes in on it, the info is in my old threads, so we can always go back and find it.
> 
> For the record, we had my TH400 disconnected and out, in under an hour, in the driveway.


Thanks army. I wrote UCC and PTC to get info from them...we'll see about cost, I think I'll pay more for the converter than I am the transmission. The cam is likely an RV-type grind to get low end power...engine was never built around high rpm racing. It's tempting to just get a $180 unit from Summit, but I know the power transfer won't compare and that is the reason I'm doing all this anyway.

I was considering doing it in the driveway, but haven't dropped a tranny out the bottom in over 15 yrs and not sure I have what I'd need to get the front of the car high enough. I think having a shop do it would keep whatever written guarantee I get valid.


----------



## armyadarkness (Dec 7, 2020)

I hadnt dropped a tranny in well over 30 years, myself, but it was a breeze... much easier than I remember... now that my toolbox consists of more than a tackle box with six wrenches and a hammer.

You and I shared the same TH400 woes... and yes I sold my soul to pay for the TKX, but it was just a game changer for me... and as it turns out, my TC was shot!

In and out, two guys could handle that job, on jack stands, in under three hours. 87.4 hours if you add in all of the shit that's going to go wrong.


----------



## ylwgto (Oct 27, 2009)

armyadarkness said:


> 87.4 hours if you add in all of the shit that's going to go wrong.


Ha, exactly....


----------



## NoGoat (Jul 21, 2021)

I’m in the middle of a trans swap at the moment
. I went this route to get off the ground enough.


----------



## ylwgto (Oct 27, 2009)

NoGoat said:


> I’m in the middle of a trans swap at the moment
> . I went this route to get off the ground enough.
> View attachment 154205



good idea! did you add 2x4 levels at corners as you jacked it up gradually?

Kinda reminds me of the El Camino-on-a-Blazer 4x4 frame trend in the 90s.

nice car, BTW.


----------



## NoGoat (Jul 21, 2021)

ylwgto said:


> good idea! did you add 2x4 levels at corners as you jacked it up gradually?
> 
> Kinda reminds me of the El Camino-on-a-Blazer 4x4 frame trend in the 90s.
> 
> nice car, BTW.


No, figured out the height needed and pre built them. Jacked it up half way on stands, then a couple 4x4s and she was up. Thank you for the compliment.


----------



## michaelfind (Dec 14, 2018)

Is there a reason you do not want to reuse your current torque converter? That would be your least expensive option, even with flushing it included in price.


----------



## ylwgto (Oct 27, 2009)

michaelfind said:


> Is there a reason you do not want to reuse your current torque converter? That would be your least expensive option, even with flushing it included in price.


It was installed back in 1999 and I cannot find my records on what stall it is or what brand. Back then I think I just told the shop to do a "shift kit" rebuild and paid no attention to converter details. I'm willing to spend a few hundred on a good converter to maximize power transfer, but still need some guidance on brand/stall speed details.


----------



## michaelfind (Dec 14, 2018)

Still, if you liked how it responded before your th400 started giving out, and everything else remains the same, you may like it again with a fresh th400. Maybe like it more if the transmission is better built?


----------



## ylwgto (Oct 27, 2009)

Some truth to that. I did like it when the tranny was working well, but ! am assuming it may be part of the problem. Maybe that is a bad assumption. 

Aside from obvious things like ballooning from racing, are there any signs of a converter going bad? Over the last decade I probably only have a few thousand miles on the car and it has spent most of its time sitting in storage (does that impact converters)?

Were I to reuse it, what need to be done to it to make sure it is fresh?


----------



## michaelfind (Dec 14, 2018)

I’m not an expert but I have swapped torque converters from one transmission to another without doing anything extra. But that was from one healthy transmission to another. If there was catastrophic or gradual failure in the transmission, then you have junk likely circulating in the fluid everywhere, including the converter. In those cases, I have had them flushed to clean out any dirty fluid. To my knowledge, they do not go bad from lack of use, especially if they are full of transmission fluid. They may call it something else these days, but I would ask the shop installing the transmission to flush or clean it internally with whatever machine they use for that purpose, then install it with your new transmission.


----------



## ylwgto (Oct 27, 2009)

Appreciate it. I may end up going that route.
I'm considering doing it myself to save the $, but if I indeed reuse the converter I'll have it cleaned out somewhere.


----------



## armyadarkness (Dec 7, 2020)

My TH400 was a fresh, performance rebuild, and it had a terrible leak.

I bought new lines for it, still leaked.

Replaced the sensors, modulators, o-rings, and sealant... still leaked.

Replaced the pan with a high quality aluminum one and used Ultra Grey... STILL LEAKED!

Then when I pulled the TH400 to instll the TKX, I put it and the converter in storage. A week later, I had to go into my storage and there was trans fluid all over the floor. It was coming from the converter. A closer inspection revealed a crack/ rupture/ pinhole, which mustve poured like crazy when spinning. I don't know if it had anything to do with my lacking performance, but Im glad it's out and done.


----------



## BearGFR (Aug 25, 2008)

ylwgto said:


> 1. What stall converter should I be looking at and what are good brands? I know not to cheap out on a converter. I have no recollection of what I currently have. Engine is a mild 400 with speed parts, but nothing crazy. 3.25 rear. mostly round town fun driving with little highway time. I like ratchet shifting and chirping tires.


Choose a converter stall RPM such that when you hammer it, it allows the engine to 'flash' up to the RPM where it's starting to make good torque. If you like how it behaves with your current transmission, then there's no reason to change converters or stall RPM. The converter I'm running in my '69 at present is from TriShield Performance. I like it a lot. If you do decide to change converters to one with a higher stall RPM, be careful not to go so far that the converter will still be "slipping" at your normal highway cruise RPM. That will cause your trans to run hotter.



ylwgto said:


> 2. is there any variability in speedo drive units year to year on these transmissions or is it all standard (I want to reuse my current one)


If you're not changing rear gear or rear tire size, then the speedo drive will be the same. I'm assuming that your current one is accurate, of course. There are two different driven gear housings for TH400's dep[ending on the driven gear size/number of teeth. I've not ever changed the driving gear that's on the trans output shaft, but I do know that it's visible if you remove the rearmost tailshaft housing (6-bolts).



ylwgto said:


> 3. I'm currently running the lines to an integrated cooler in an aftermarket, fully shrouded aluminum radiator. Is this sufficient or should I go back to an external trans cooler (always hated the way the soft lines look going under the radiator core support)?


If you don't have transmission heat problems now, and don't change converters, then your current setup should be fine.



ylwgto said:


> 4. any benefit to a poly trans mount over the standard style?


Poly mounts are 'stiffer' and don't deflect as much as a rubber mount. If you decide to change mounts, be careful that the new mount is exactly the same height as the old mount. Changing the height will change the ujoint operating angle and unless you "tilt" the rear axle by exactly the same amount, you're likely to introduce vibration in the drive line. 



ylwgto said:


> 5. for a tranny shop this should be no more than a 3hr job including a pan drop to put a new filter and fluid in. That sound reasonable?


Depends on the shop, but that sounds reasonable.



ylwgto said:


> 6. anything to be done about my weepy rear main seal without dropping the oil pan (wishful thinking here I imagine)? I am going to photo the back of the crank to make sure it is cast to receive a pilot bushing for my manual conversion someday.


How "weepy"? Dropping the pan on a Pontiac is not a trivial operation. Considering how high you have to lift the engine to get enough room to remove it, it's usually easier to just pull the engine. For sure it's easer to replace the seal with the engine out.

Bear


----------



## ylwgto (Oct 27, 2009)

Thanks Bear! Super helpful.

I changed my wheels/tires and rear gear last year. never even thought about updating the speedometer gear, so it is probably not accurate currently. not a huge concern to me, but if it is easy to deal with I'd try and make it accurate.

Rear main is a couple small drops a day...not enough to go through the effort of dropping the pan while in the car. I did that once and that gasket(s) are a PITA.

Working my courage up to do this in the driveway...main barrier is getting car high enough.

How much fluid do you pre-fill the converter with before putting the transmission back in?

Thanks


----------



## NoGoat (Jul 21, 2021)

ylwgto said:


> Thanks Bear! Super helpful.
> 
> I changed my wheels/tires and rear gear last year. never even thought about updating the speedometer gear, so it is probably not accurate currently. not a huge concern to me, but if it is easy to deal with I'd try and make it accurate.
> 
> ...


Extreme Automatics said you don't need to, pump fills it super fast at startup. If you want to add, I've always heard 1 quart.

As for getting it high enough. I went to Home Depot and bought some 2x4s from their "cull wood rack" at 70% off. The pieces you need to make those wheel cribs are so small a little curve or warping is of no consequence. Ended up about $35. A lot of cutting and screwing (watch it!). Then I jacked the car up to the full jack stand height, then used a couple 4x4s joined together to get the remaining height. 15 inch cribs gave me 25 inches of frame to ground clearance. If I can do it, "YOU CAN DO IT!"


----------



## armyadarkness (Dec 7, 2020)

ylwgto said:


> Thanks Bear! Super helpful.
> 
> I changed my wheels/tires and rear gear last year. never even thought about updating the speedometer gear, so it is probably not accurate currently. not a huge concern to me, but if it is easy to deal with I'd try and make it accurate.
> 
> ...


If you read my TKX thread, there's a detailed requirements and procedure for removing the TH400


----------



## armyadarkness (Dec 7, 2020)

I performed my entire TKX swap, including removing the TH400, with the car like this.








FAQ - Powetrain: TREMEC TKX - Automatic to Manual Conversion


This is my final write up for the swap. It is NOT ANY CHEAPER to do a Muncie than a Tremec.. in fact, it's more expensive. A quality Muncie rebuild is going to cost over $2500 and you wont have overdrive. So, yes, you can buy a used cheap Muncie, but that's on you if you choose to forgo the...




www.gtoforum.com


----------



## michaelfind (Dec 14, 2018)

NoGoat said:


> Extreme Automatics said you don't need to, pump fills it super fast at startup. If you want to add, I've always heard 1 quart.
> 
> As for getting it high enough. I went to Home Depot and bought some 2x4s from their "cull wood rack" at 70% off. The pieces you need to make those wheel cribs are so small a little curve or warping is of no consequence. Ended up about $35. A lot of cutting and screwing (watch it!). Then I jacked the car up to the full jack stand height, then used a couple 4x4s joined together to get the remaining height. 15 inch cribs gave me 25 inches of frame to ground clearance. If I can do it, "YOU CAN DO IT!"
> View attachment 154234


I've always been told and used 1 quart in the torque converter before installing it too. It's easy to pour a quart into the TC before putting it on the shaft and if it provides any benefit, it easily outweighs the "trouble" of doing it. It certainly is not damaging anything in any way.


----------



## ylwgto (Oct 27, 2009)

thanks, guys


----------



## ylwgto (Oct 27, 2009)

armyadarkness said:


> I performed my entire TKX swap, including removing the TH400, with the car like this.
> 
> 
> 
> ...


Did you weld up those stands? I was thinking of going to my buddies wrecking yard for 8 steel wheels for stacking like they do at the yard...seems plenty strong (i've seen cars stacked 4 high on em). Like a 15" on top of 16" so it is a slot-fit.


----------



## armyadarkness (Dec 7, 2020)

ylwgto said:


> Did you weld up those stands? I was thinking of going to my buddies wrecking yard for 8 steel wheels for stacking like they do at the yard...seems plenty strong (i've seen cars stacked 4 high on em). Like a 15" on top of 16" so it is a slot-fit.


Yes I welded them. I leave them on their sides for little stuff, but I can put the entire car 2 feet in the air if I stand them up, and they're much sturdier than a regular stand. Just one would hold up the entire car.


----------



## armyadarkness (Dec 7, 2020)

I also welded up that floor jack adapter to lower the TH400


----------



## ylwgto (Oct 27, 2009)

Noticed that, nice. If I find time to do this on my trip I'll have to cludge together a cradle for my floor jack too (probably from wood though). did you support your oil pan to prevent the block from tipping or did your exhaust hold it in place?


----------



## armyadarkness (Dec 7, 2020)

My engine didnt budge. No, I didnt support it at all. My mounts were fairly new


----------



## ylwgto (Oct 27, 2009)

What’s the fluid capacity on a standard depth pan th400? Just looking for ballpark for the initial fill before fine tuning once car is back on ground and running warm.

Any favorite Dex 3 fluid brands more suitable for performance transmissions over parts store stuff?


----------



## ylwgto (Oct 27, 2009)

Picked the transmission up today. It looks to be in fantastic shape and ended up coming with a nearly new TCI 10” breakaway converter (2400 stall) and an sfi rated flex plate. Eager to do this job myself when I have time now.

can anyone recommend a good source for the technical aspects of the job (how much t fluid to add and torq specs for flywheel, converter, bellhousing, u joint bolts etc)?

Do you all reuse bolts or should I buy new bolts all around?

do I have to pull the starter? If so is it ok to hang it with a zip tie so wiring stays attached?

and does the dipstick tube get installed after the new transmission is bolted in?


----------



## armyadarkness (Dec 7, 2020)

You don't have to pull the starter.
I just use ANY Dex 3 fluid, that NAPA sells.
You can reuse the old bolts.
I would personally use a Summit Aluminum pan with drain. It seals so much better, it holds more fluid, and it drains!!! That being said... capacity specs are everywhere, but you should always just fill the pan, start the car, put it in each gear with your foot on the brake, and then recheck it. Add more until it reads full in park.



https://butlerperformance.com/p-34888-pontiac-engine-torque-specs.html


----------



## ylwgto (Oct 27, 2009)

armyadarkness said:


> You don't have to pull the starter.
> I just use ANY Dex 3 fluid, that NAPA sells.
> You can reuse the old bolts.
> I would personally use a Summit Aluminum pan with drain. It seals so much better, it holds more fluid, and it drains!!! That being said... capacity specs are everywhere, but you should always just fill the pan, start the car, put it in each gear with your foot on the brake, and then recheck it. Add more until it reads full in park.
> ...



Thanks, helpful.

It's got an aftermarket pan on it with a drain plug already (bonus). Considering changing gasket and filter before I install just because I do not know the history.


----------



## Droach6498 (Nov 1, 2020)

Been praising wheel cribs for awhile now 20" x 16" Im just using them here for stops no ebrake


----------

