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So, I'm a total newbie on automatics. Always have been using manuals.
I took the leap and got a built 350 (I think they are called 370), with a hughes transbrake. I had a read through the information from hughes and there are some limitations in it.
About the burnout: Start in second gear and shift up to third and finish burnout. DO NOT start in first!
Why? I'm just curious.
Same with down shifts. No down shifts what so ever. If the wheels are turning, ju can't shift down.
Why?
Can some one help me get some clarity to this?
Any other don'ts I should be aware of? Or do's for that matter?
LOL jeez man give the guy a break he's only got 2 posts!!!
OP lots of help on this forum, just try to confirm what you're posting first and while it is cumbersome to make a long thread it is helpful to be as descriptive as possible.
@ Jays_SSZ28 Ok, ok... take it easy. Like I said, I am a newbie on autos.
Thats what the guy who built the trans said. Because I thought it was a 400, but he said it wasn't. it was a 350 and to handle my 700 ish he had to change the output shaft. Thats all I know.
Now, I trust him, but I may have misunderstood him on something? I can for certain say that it is a 32 spline.
I'm happy to listen and learn.
The transmission is in the car already. It was out of a van, can't remember what year though. -87 maybe? What do you want a picture of?
@allblackedout5 I tried searching, but I don't really know what to search for. I spent at least 20 minutes searching and apparently I don't even know what transmission I have.
Sorry if I mess up the writing and being hard to understand. I'm not a native english speaker.
Thanks for the help though
This is the easier way to check which transmission you have. Take a look at the shape of your pan and see which one matches.
(not my pic, found on google images)
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The th375 only came out in the mid to late 70's and had 375 cast into the tail housing and uses a 27 spline output AND has less clutches. I DO NOT CARE WHAT ANYONE ELSE SAYS. GM ALSO came out with the same transmission in the late 80's early 90's and put them in 3/4 ton trucks. 27 spline outputs but no 375 on the tail housing. Otherwise identical to a th400. My best friends father had a 3/4 ton truck with this transmission in it and it also said HD on the bellhousing. He bought this brand new from the dealer and I later owned it.
So do you have a th400 or th350?
The th400 probably has no front band so if you downshift from 3rd the intermediate drum will overrun and possibly fly through the case. I'm guessing also it's full manual?
I built a th400 like this and a guy that works at Hughes who is on a forum told me this. No front band, do not downshift at speed.
You are absolutely....positively wrong about not being able to downshift from 3rd. You can do so, but just need to know how. If you downshift to 2nd while applying part throttle, it's fine. The problem comes when you let the motor drop to idle in 2nd.... and then stand in it, which will likely kill the sprag. And whoever this guy is at hughes that told you so, should be ashamed for misinforming you like this.
You are absolutely....positively wrong about not being able to downshift from 3rd. You can do so, but just need to know how. If you downshift to 2nd while applying part throttle, it's fine. The problem comes when you let the motor drop to idle in 2nd.... and then stand in it, which will likely kill the sprag. And whoever this guy is at hughes that told you so, should be ashamed for misinforming you like this.
You absolutely...positively didn't understand what I said at all.
My explanation was based on a run down the drag strip. Since it starts with a burnout, etc.
Didn't explain how to downshift at all, I just said duplicate what it would do in stock form. For example, yes, you could cruise down the highway and give it throttle while downshifting. Thats what would happen in stock form right? On the other hand no, you don't want to put it in neutral and coast or drop down to second without throttle.
My explanation is solely based on a run down the drag strip. Thats why it starts with a burnout and ends with don't put it in neutral at speed.
I built drove a RMVB th400 and drove it behind a 468 that would turn 8500 rpm on the street and track, I know how to drive it, I had the car 19 years. I'm not a ******* teacher for explaining how to drive a 32 spline th350 that doesn't exist, never said I was tech support either.
Maybe I should be ashamed of explaining something that doesn't cover every possible scenario you might find yourself in and how to drive your 32 spline th350 during each one.
There were TH350's that had the ID TH375. They were HD versions of the TH350. They came in Buicks if I remember correctly. And as stated there were TH375 versions of a TH400. Both not very common at all. I will not build a "reverse pattern" valve bodies for safety reasons. Each to their own on this though.
Yes, there was additional clutch (five) in direct. As well as a bearing on the front planetary, and a bearing on the backside of the rear planetary instead of a thrust washer on each. The spline count on the output shaft never changed, just the length.
Jays_SSZ28: Ok, my bad. It is a 400. I just checked the oilpan. I guess I got it all wrong.
So it's tricky to drive on the street?
When I do, can you help me and explain how to down shift at speed coming to a stop and how to at speed, maintaining speed?
I think I understunderstand.
Could I 3-2 shift with no throttle at the correct speed for second gear? At, let's say 20 mph?
Or is it the no throttle that is the issue?
Is it the pump rpm that is the problem with not having any throttle at downshift?
that would explain the need for engine braking.
I'm trying to grasp how an automatic works.
02-22-2018, 07:27 AM
Do's and don'ts th350/370 or th400 
