TH400Code for 4BT's?

[Slaughter]

I am lookin for info on the Turbo 400's put in bread trucks. Specifically 1) What Torque Converter did they use? GM? 3 or 6 bolt to flex plate? 2) What valve body did they use? 3) What was the 2 letter production code? 4) Was the valve body any different from other TH400's? 5) What make manual modulator did they use? Thanks Scott:-{}

 

[jlast]

I do not know specific answers but, i assume they would be exactly the same as any 2wd diesel GM th400 trans. I doubt that they would come with the th475 which is the 6 bolt converter and the straight cut gears that came in buses and larger trucks, usually have the parking brake drums on the back.



not exactly sure why you are looking for this? any th400 can handle the power of the 4bt, but the converter would have to be different, not exactly sure if a GM diesel converter is a good match for the 4bt.



Please let me or us know what you find out.

Might try diesel depot sometimes called avant salvage suppose to be the same place i guess. deals in medium and heavy trucks seen them list a few 4bts on ebay as well as adapters and such out of bread trucks.



Jamie Avant

478-552-9510

 

[Slaughter]

The TH475 would be nice...

I am wondering, not about the strength, but about how the shift points are adjusted for the torque curve of the 4BT. (ie is the valve body different or just the modulator, manual no doubt, adjusted to compensate for the narrower 4BT torque band) They are obviously different from the gasser TH400 and probably from the 6. 2/6. 5 GM diesel, which has a different RPM/torque curve. I am also hoping the sprags in the planetaries are the "dog bone" type. The torque converter has to be a much lower stall series, but I think GM has only 2 that are stock, the question is, Which ones? What are the specs? BTW Avant is the next call... ...

 

[pmartinez]

I work for a bread company. I currently have a truck in the shop that has one of these engine and transmission combinations. I will look to see if there are any numbers on the transmission. I myself have rebuilt one of these transmissions and could not figure out how they make this thing shift. The modulator is a modified unit which I could not find a replacement. I myself did a conversion on a chevy 6bt/t400 and used a modified vacuum valve from a chevy 6. 2 diesel. It works fairly well. I installed it on the top of the injection pump. I will let you know the numbers if I find any tomorrow.

 

[243]

PMartinez,



Please try to find out how the vacuum modulator works on the bread vans. Specifically, how do you supply vacuum and how is it synchronized with engine rpm to control the modulator?



B&M used to make a device called the Modulink. It fit in place of the modulator. It was cable operated off the carb to move the same rod the modulator controls. It was marketed for supercharged or turboed gas motors or vehicles with a big cam which did not have enough vacuum to operate the trans.

 

[Slaughter]

Any new info?

Still trying to find out which t400's were in the bread trucks. Anyone know where the specific types of internals (clutch pak, valve body #'s) can be spec'd? Thanks

 

[DKarvwnaris]

Last 400 transmission I bought for a cummins repower was purchased directly from a GM medium truck dealer. I speced it specifically for the p-30 platform with the 4bt engine. I will see if I can find the paperwork on it, it has been over 2 years since I had to locate one. I have convinced most friends to go with the dodge automatics, less headaches. You should be able to go to any dealer that services or sells the p-30 platform chassis.

 

[britannic]

Slaughter, if you're still looking for a TH400, I have one out of a military diesel that works great. Comes complete with the 6 lug diesel torque converter. I also have a vacuum regulator valve that you could adapt to your inj. pump so you can control the shifts. PM me if you're interested. The other control it uses is a WOT switched kickdown.

Originally posted by Slaughter

I am lookin for info on the Turbo 400's put in bread trucks. Specifically 1) What Torque Converter did they use? GM? 3 or 6 bolt to flex plate? 2) What valve body did they use? 3) What was the 2 letter production code? 4) Was the valve body any different from other TH400's? 5) What make manual modulator did they use? Thanks Scott:-{}

 

[BJMarshall]

I just got a new converter for mine today. I'll send you the dacco number as soon as I look at it again. Stall is perfect. The main difference on the transmission is the governor. It has real heavy weights and springs to make it shift earlier. I would think it is the same as the governor on a hummer. The moduator has been replaced with an adjustment screw. You can adjust how firm and how late it shifts. The modulator is basically a pressure regulator. Screw it in and it shifts later and harder. The only problem with this is it is going to shift this way all the time. It's not going to shift soft when you are easing along and firm when you are on the throttle. Mine shifts at about 2200 all the time. It's a little aggravating, but it's not that bad.

I found out the hard way that you have to watch the torque converter bolts. Mine loosened up and ruined the flywheel, converter, adapter and hub. $650 later and $3 for some loctite and it is fine. I will still watch them though.

 

[BJMarshall]

The Dacco part number for the 400 converter is B6. I've got one behind my 4bt now and it works great. Also another difference I found on the 400 was the pan. It is a big cast aluminum piece that also bolts to the engine adapter plate. Words might not mean much. Could send you a picture if you like. Internally, I didn't see anything much different form a regular 400.